jasmonic-acid and Disease-Resistance

Topics: Abscisic Acid; Colletotrichum; Crops, Agricultural; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Humans; Indoleacetic Acids; Metabolic Networks and Pathways; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants; Salicylic Acid

Sensing of pathogen infection by plants elicits early signals that are transduced to affect defense mechanisms, such as effective blockage of pathogen entry by regulation of stomatal closure, cuticle, or callose deposition, change in water potential, and resource acquisition among many others. Pathogens, on the other hand, interfere with plant physiology and protein functioning to counteract plant defense responses. In plants, hormonal homeostasis and signaling are tightly regulated; thus, the phytohormones are qualified as a major group of signaling molecules controlling the most widely tinkered regulatory networks of defense and counter-defense strategies. Notably, the phytohormone jasmonic acid mediates plant defense responses to a wide array of pathogens. In this review, we present the synopsis on the jasmonic acid metabolism and signaling, and the regulatory roles of this hormone in plant defense against the hemibiotrophic bacterial pathogen

Topics: Cyclopentanes; Disease Resistance; Host-Pathogen Interactions; Metabolic Networks and Pathways; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Pseudomonas syringae; Signal Transduction; Virulence

Volatiles mediate the interaction of plants with pollinators, herbivores and their natural enemies, other plants and micro-organisms. With increasing knowledge about these interactions the underlying mechanisms turn out to be increasingly complex. The mechanisms of biosynthesis and perception of volatiles are slowly being uncovered. The increasing scientific knowledge can be used to design and apply volatile-based agricultural strategies.

Topics: Agriculture; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Herbivory; Oxylipins; Phenols; Plants; Pollination; Signal Transduction; Terpenes; Volatile Organic Compounds

The channeling of metabolites is an essential step of metabolic regulation in all living organisms. Multifunctional enzymes with defined domains for metabolite compartmentalization are rare, but in many cases, larger assemblies forming multimeric protein complexes operate in defined metabolic shunts. In

Topics: Aldehyde-Lyases; Amino Acid Sequence; Arabidopsis; Chloroplasts; Cyclopentanes; Cytochrome P-450 Enzyme System; Disease Resistance; Intramolecular Oxidoreductases; Metabolic Networks and Pathways; Models, Molecular; Multiprotein Complexes; Oxylipins; Plant Development; Protein Binding; Structure-Activity Relationship

Global crop production is highly threatened due to pathogen invasion. The huge quantity of pesticides application, although harmful to the environment and human health, is carried out to prevent the crop losses worldwide, every year. Therefore, understanding the molecular mechanisms of pathogenicity and plant resistance against pathogen is important. The resistance against pathogens is regulated by three important phytohormones viz. salicylic acid (SA), jasmonic acid (JA) and ethylene (ET). Here we review possible role of CRISPR technology to understand the plant pathogenicity by mutating genes responsible for pathogen invasion or up-regulating the phytohormones genes or resistant genes. Thus hormone biosynthesis genes, receptor and feeding genes of pathogens could be important targets for modifications using CRISPR/Cas9 following multiplexing tool box strategy in order to edit multiple genes simultaneously to produce super plants. Here we put forward our idea thatthe genes would be either mutated in case of plant receptor protein targets of pathogens or up-regulation of resistant genes or hormone biosynthesis genes will be better choice for resistance against pathogens.

Topics: Animals; Bacteria; Bacterial Proteins; CRISPR-Associated Protein 9; CRISPR-Cas Systems; Crops, Agricultural; Cyclopentanes; Disease Resistance; Endonucleases; Ethylenes; Fungi; Gene Editing; Genome, Plant; Mutation; Nematoda; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Salicylic Acid

Various cool-season grasses are infected by Epichloë endophyte, and this symbiotic relationship is always of benefit to the host grass due to an increased resistance to abiotic and biotic stresses. Fungal diseases adversely affect the yield, quality, and economic benefits of rangelands, which affects the production of animal husbandry. Therefore, it is imperative to breed resistant cultivars and to better understand the role of fungal endophytes in order to protect grasses against pathogens. The present review introduces research regarding how these endophytes affect the growth of pathogens in vitro and how they change the resistance of host plants to plant diseases. From the perspective of physical defense, changes in physiological indexes, and secretion of chemical compounds, we summarize the potential mechanisms by which endophytes are able to enhance the disease resistance of a host grass. Through these, we aim to establish a solid theoretical foundation for plant disease control and disease resistance breeding by application of fungal endophytes. A broader understanding of fungal endophyte effects on hosts could create a new opportunity for managing or introducing fungal symbioses in both agronomic or non-agronomic ecosystems.

Topics: Cyclopentanes; Disease Resistance; Endophytes; Epichloe; Host-Pathogen Interactions; Oxylipins; Plant Breeding; Plant Diseases; Plant Growth Regulators; Plant Leaves; Poaceae; Salicylates; Signal Transduction; Symbiosis

The plant hormone jasmonate (JA) exerts direct control over the production of chemical defense compounds that confer resistance to a remarkable spectrum of plant-associated organisms, ranging from microbial pathogens to vertebrate herbivores. The underlying mechanism of JA-triggered immunity (JATI) can be conceptualized as a multi-stage signal transduction cascade involving: i) pattern recognition receptors (PRRs) that couple the perception of danger signals to rapid synthesis of bioactive JA; ii) an evolutionarily conserved JA signaling module that links fluctuating JA levels to changes in the abundance of transcriptional repressor proteins; and iii) activation (de-repression) of transcription factors that orchestrate the expression of myriad chemical and morphological defense traits. Multiple negative feedback loops act in concert to restrain the duration and amplitude of defense responses, presumably to mitigate potential fitness costs of JATI. The convergence of diverse plant- and non-plant-derived signals on the core JA module indicates that JATI is a general response to perceived danger. However, the modular structure of JATI may accommodate attacker-specific defense responses through evolutionary innovation of PRRs (inputs) and defense traits (outputs). The efficacy of JATI as a defense strategy is highlighted by its capacity to shape natural populations of plant attackers, as well as the propensity of plant-associated organisms to subvert or otherwise manipulate JA signaling. As both a cellular hub for integrating informational cues from the environment and a common target of pathogen effectors, the core JA module provides a focal point for understanding immune system networks and the evolution of chemical diversity in the plant kingdom.

Topics: Animals; Bacteria; Cyclopentanes; Disease Resistance; Fungi; Herbivory; Host-Pathogen Interactions; Oxylipins; Plant Immunity; Plant Proteins; Plants; Repressor Proteins; Signal Transduction

Hormone signaling crosstalk plays a major role in plant defense against a wide range of both biotic and abiotic stresses. While many reviews on plant-microbe interactions have well described the general trends of signaling pathways in shaping host responses to pathogens, few discussions have considered a synthesis of positive versus negative interactions among such pathways, or variations in the signaling molecules themselves. This review deals with the interaction trends between salicylic, jasmonic, and abscisic acids in the signaling pathways, as well as exceptions to such trends. Here we focused on antagonistic versus cooperative interactions between salicylic and jasmonic acids, two major disease resistance signaling molecules, and some interactions with abscisic acid, a known abiotic stress hormone, and another player in plant defense mechanisms. We provide a set of examples materializing either antagonism or cooperation for each interaction between two pathways, thereby showing the trends and pinpointing the exceptions. Such analyses are practical for researchers working on the subject and essential for a better exploitation of the data already available in plant disease resistance signaling, both in Arabidopsis and crop species, toward the development of better disease management strategies for economically important crops.

Topics: Abscisic Acid; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Physiological Phenomena; Plants; Salicylic Acid; Signal Transduction

Jasmonic acid (JA) plays an important role in regulating plant growth and defence responses. Here, we show that a transcription factor that belongs to the B-box (BBX) family named SlBBX20 regulates resistance to Botrytis cinerea in tomato by modulating JA signalling. The response to JA was significantly suppressed when SlBBX20 was overexpressed in tomato. By contrast, the JA response was enhanced in SlBBX20 knockout lines. RNA sequencing analysis provided more evidence that SlBBX20 modulates the expression of genes that are involved in JA signalling. We found that SlBBX20 interacts with SlMED25, a subunit of the Mediator transcriptional co-activator complex, and prevents the accumulation of the SlMED25 protein and transcription of JA-responsive genes. JA contributes to the defence response against necrotrophic pathogens. Knocking out SlBBX20 or overexpressing SlMED25 enhanced tomato resistance to B. cinerea. The resistance was impaired when SlBBX20 was overexpressed in plants that also overexpressed SlMED25. These data show that SlBBX20 attenuates JA signalling by regulating SlMED25. Interestingly, in addition to developing enhanced resistance to B. cinerea, SlBBX20-KO plants also produced higher fruit yields. SlBBX20 is a potential target gene for efforts that aim to develop elite crop varieties using gene editing technologies.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Signal Transduction; Solanum lycopersicum

Although germin-like proteins (GLPs) have been demonstrated to participate in plant biotic stress responses, their specific functions in rice disease resistance are still largely unknown. Here, we report the identification and characterization of OsGLP3-7, a member of the GLP family in rice. Expression of OsGLP3-7 was significantly induced by pathogen infection, jasmonic acid (JA) treatment, and hydrogen peroxide (H

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Hydrogen Peroxide; Metabolic Networks and Pathways; Oryza; Oxylipins; Phytoalexins; Plant Diseases; Plant Proteins

GhSCL13-2A, a member of the PAT1 subfamily in the GRAS family, positively regulates cotton resistance to Verticillium dahliae by mediating the jasmonic acid and salicylic acid signaling pathways and accumulation of reactive oxygen species. Verticillium wilt (VW) is a devastating disease of upland cotton (Gossypium hirsutum) that is primarily caused by the soil-borne fungus Verticillium dahliae. Scarecrow-like (SCL) proteins are known to be involved in plant abiotic and biotic stress responses, but their roles in cotton defense responses are still unclear. In this study, a total of 25 GhPAT1 subfamily members in the GRAS family were identified in upland cotton. Gene organization and protein domain analysis showed that GhPAT1 members were highly conserved. GhPAT1 genes were widely expressed in various tissues and at multiple developmental stages, and they were responsive to jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) signals. Furthermore, GhSCL13-2A was induced by V. dahliae infection. V. dahliae resistance was enhanced in Arabidopsis thaliana by ectopic overexpression of GhSCL13-2A, whereas cotton GhSCL13-2A knockdowns showed increased susceptibility. Levels of reactive oxygen species (ROS) and JA were also increased and SA content was decreased in GhSCL13-2A knockdowns. At the gene expression level, PR genes and SA signaling marker genes were down-regulated and JA signaling marker genes were upregulated in GhSCL13-2A knockdowns. GhSCL13-2A was shown to be localized to the cell membrane and the nucleus. Yeast two-hybrid and luciferase complementation assays indicated that GhSCL13-2A interacted with GhERF5. In Arabidopsis, V. dahliae resistance was enhanced by GhERF5 overexpression; in cotton, resistance was reduced in GhERF5 knockdowns. This study revealed a positive role of GhSCL13-2A in V. dahliae resistance, establishing it as a strong candidate gene for future breeding of V. dahliae-resistant cotton cultivars.

Topics: Ascomycota; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Plant Breeding; Plant Diseases; Plant Proteins; Reactive Oxygen Species; Salicylic Acid; Verticillium

The WRKY transcription factors play significant roles in plant growth, development, and defense responses. However, in cotton, the molecular mechanism of most WRKY proteins and their involvement in Verticillium wilt tolerance are not well understood.. GhWRKY70 is greatly up-regulated in cotton by Verticillium dahliae. Subcellular localization suggests that GhWRKY70 is only located in the nucleus. Transcriptional activation of GhWRKY70 further demonstrates that GhWRKY70 function as a transcriptional activator. Transgenic Arabidopsis plants overexpressing GhWRKY70 exhibited better growth performance and higher lignin content, antioxidant enzyme activities and jasmonic acid (JA) levels than wild-type plants after infection with V. dahliae. In addition, the transgenic Arabidopsis resulted in an enhanced expression level of AtAOS1, a gene related to JA synthesis, further leading to a higher JA accumulation compared to the wild type. However, the disease index (DI) values of the VIGS-treated cotton plants with TRV:WRKY70 were also significantly higher than those of the VIGS-treated cotton plants with TRV:00. The chlorophyll and lignin contents of TRV:WRKY70 plants were significantly lower than those of TRV:00 plants. GhAOS1 expression and JA abundance in TRV:WRKY70 plants were decreased. The GhWRKY70 protein was confirmed to bind to the W-box element in the promoter region of GhAOS by yeast one-hybrid assay and transient expression.. These results indicate that the GhWRKY70 transcription factor is a positive regulator in Verticillium wilt tolerance of cotton, and may promote the production of JA via regulation of GhAOS1 expression.

Topics: Arabidopsis; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Lignin; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Transcription Factors; Verticillium

Rice blast, caused by the fungal pathogen Magnaporthe oryzae, is one of the most devastating diseases in rice (Oryza sativa L.). Plant annexins are calcium- and lipid-binding proteins that have multiple functions; however, the biological roles of annexins in plant disease resistance remain unknown. Here, we report a rice annexin gene, OsANN1 (Rice annexin 1), that was induced by M. oryzae infection and negatively regulated blast disease resistance in rice. By yeast 2-hybrid screening, we found that OsANN1 interacted with a cytochrome P450 monooxygenase, HAN1 ("HAN" termed "chilling" in Chinese), which has been reported to catalyze the conversion of biologically active jasmonoyl-L-isoleucine (JA-Ile) to the inactive form 12-hydroxy-JA-Ile. Pathogen inoculation assays revealed that HAN1 was also a negative regulator in rice blast resistance. Genetic evidence showed that OsANN1 acts upstream of HAN1. OsANN1 stabilizes HAN1 in planta, resulting in the inactivation of the endogenous biologically active JA-Ile. Taken together, our study unravels a mechanism where an OsANN1-HAN1 module impairs blast disease resistance via inactivating biologically active JA-Ile and JA signaling in rice.

Topics: Annexins; Calcium-Binding Proteins; Cyclopentanes; Disease Resistance; Magnaporthe; Oryza; Plant Diseases; Plant Proteins

Lignins and their antimicrobial-related polymers cooperatively enhance plant resistance to pathogens. Several isoforms of 4-coumarate-coenzyme A ligases (4CLs) have been identified as indispensable enzymes involved in lignin and flavonoid biosynthetic pathways. However, their roles in plant-pathogen interaction are still poorly understood. This study uncovers the role of Gh4CL3 in cotton resistance to the vascular pathogen Verticillium dahliae. The cotton 4CL3-CRISPR/Cas9 mutant (CR4cl) exhibited high susceptibility to V. dahliae. This susceptibility was most probably due to the reduction in the total lignin content and the biosynthesis of several phenolic metabolites, e.g., rutin, catechin, scopoletin glucoside, and chlorogenic acid, along with jasmonic acid (JA) attenuation. These changes were coupled with a significant reduction in 4CL activity toward p-coumaric acid substrate, and it is likely that recombinant Gh4CL3 could specifically catalyze p-coumaric acid to form p-coumaroyl-coenzyme A. Thus, overexpression of Gh4CL3 (OE4CL) showed increasing 4CL activity that augmented phenolic precursors, cinnamic, p-coumaric, and sinapic acids, channeling into lignin and flavonoid biosyntheses and enhanced resistance to V. dahliae. Besides, Gh4CL3 overexpression activated JA signaling that instantly stimulated lignin deposition and metabolic flux in response to pathogen, which all established an efficient plant defense response system, and inhibited V. dahliae mycelium growth. Our results propose that Gh4CL3 acts as a positive regulator for cotton resistance against V. dahliae by promoting JA signaling-mediated enhanced cell wall rigidity and metabolic flux.

Topics: Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Ligases; Lignin; Plant Diseases; Plant Proteins; Verticillium

Plants have evolved sophisticated mechanisms to detect various forms of danger. Damage-associated molecular patterns (DAMPs) are endogenous danger molecules that are released from damaged cells and activate the innate immunity. Recent evidence suggests that plant extracellular self-DNA (esDNA) can serve as a DAMP molecule. However, the mechanisms by which esDNA functions are largely unknown. In this study, we confirmed that esDNA inhibits root growth and triggers reactive oxygen species (ROS) production in a concentration- and species-specific manner in Arabidopsis (Arabidopsis thaliana) and tomato (Solanum lycopersicum L.). Furthermore, by combining RNA sequencing, hormone measurement, and genetic analysis, we found that esDNA-mediated growth inhibition and ROS production are achieved through the jasmonic acid (JA) signaling pathway. Specifically, esDNA induces JA production and the expression of JA-responsive genes. The esDNA-mediated growth inhibition, ROS production, and gene expression are impaired in the JA-related mutants. Finally, we found that the JA signaling pathway is required for the esDNA-elicited resistance against the pathogens Botrytis cinerea and Pseudomonas syringae pv. tomato DC3000. This finding highlights the importance of JA signaling in esDNA-mediated biological effects, thereby providing insight into how esDNA functions as a DAMP.

Topics: Arabidopsis; Cyclopentanes; Disease Resistance; DNA; Gene Expression Regulation, Plant; Humans; Oxylipins; Plant Diseases; Plant Immunity; Pseudomonas syringae; Reactive Oxygen Species; Signal Transduction

Rhizoctonia solani is a devastating soil-borne pathogen that seriously threatens the cultivation of economically important crops. Multiple strains with a very broad host range have been identified, but only 1 (AG1-IA, which causes rice sheath blight disease) has been examined in detail. Here, we analyzed AG4-HGI 3 originally isolated from Tartary buckwheat (Fagopyrum tataricum), but with a host range comparable to AG1-IA. Genome comparison reveals abundant pathogenicity genes in this strain. We used multiomic approaches to improve the efficiency of screening for disease resistance genes. Transcriptomes of the plant-fungi interaction identified differentially expressed genes associated with virulence in Rhizoctonia and resistance in Tartary buckwheat. Integration with jasmonate-mediated transcriptome and metabolome changes revealed a negative regulator of jasmonate signaling, cytochrome P450 (FtCYP94C1), as increasing disease resistance probably via accumulation of resistance-related flavonoids. The integration of resistance data for 320 Tartary buckwheat accessions identified a gene homolog to aspartic proteinase (FtASP), with peak expression following R. solani inoculation. FtASP exhibits no proteinase activity but functions as an antibacterial peptide that slows fungal growth. This work reveals a potential mechanism behind pathogen virulence and host resistance, which should accelerate the molecular breeding of resistant varieties in economically essential crops.

Topics: Disease Resistance; Fagopyrum; Gene Expression Profiling; Multiomics; Plant Proteins; Rhizoctonia; Virulence

Phospholipid signaling plays important roles in plant immune responses. Here, we focused on two phospholipase C3 (PLC3) orthologs in the Nicotiana benthamiana genome, NbPLC3-1 and NbPLC3-2. We generated NbPLC3-1 and NbPLC3-2-double-silenced plants (NbPLC3s-silenced plants). In NbPLC3s-silenced plants challenged with Ralstonia solanacearum 8107, induction of hypersensitive response (HR)-related cell death and bacterial population reduction was accelerated, and the expression level of Nbhin1, a HR marker gene, was enhanced. Furthermore, the expression levels of genes involved in salicylic acid and jasmonic acid signaling drastically increased, reactive oxygen species production was accelerated, and NbMEK2-induced HR-related cell death was also enhanced. Accelerated HR-related cell death was also observed by bacterial pathogens Pseudomonas cichorii, P. syringae, bacterial AvrA, oomycete INF1, and TMGMV-CP with L1 in NbPLC3s-silenced plants. Although HR-related cell death was accelerated, the bacterial population was not reduced in double NbPLC3s and NbCoi1-suppressed plants nor in NbPLC3s-silenced NahG plants. HR-related cell death acceleration and bacterial population reduction resulting from NbPLC3s-silencing were compromised by the concomitant suppression of either NbPLC3s and NbrbohB (respiratory oxidase homolog B) or NbPLC3s and NbMEK2 (mitogen activated protein kinase kinase 2). Thus, NbPLC3s may negatively regulate both HR-related cell death and disease resistance through MAP kinase- and reactive oxygen species-dependent signaling. Disease resistance was also regulated by NbPLC3s through jasmonic acid- and salicylic acid-dependent pathways.

Topics: Disease Resistance; Gene Expression Regulation, Plant; Mitogen-Activated Protein Kinases; Nicotiana; Plant Diseases; Plant Growth Regulators; Plant Proteins; Reactive Oxygen Species; Salicylic Acid

Glycoside hydrolase (GH) family members act as virulence factors and regulate plant immune responses during pathogen infection. Here, we characterized the GH28 family member endopolygalacturonase VdEPG1 in Verticillium dahliae. VdEPG1 acts as a virulence factor during V. dahliae infection. The expression level of VdEPG1 was greatly increased in V. dahliae inoculated on cotton roots. VdEPG1 suppressed VdNLP1-mediated cell death by modulating pathogenesis-related genes in Nicotiana benthamiana. Knocking out VdEPG1 led to a significant decrease in the pathogenicity of V. dahliae in cotton. The deletion strains were more susceptible to osmotic stress and the ability of V. dahliae to utilize carbon sources was deficient. In addition, the deletion strains lost the ability to penetrate cellophane membrane, with mycelia showing a disordered arrangement on the membrane, and spore development was affected. A jasmonic acid (JA) pathway-related gene, GhOPR9, was identified as interacting with VdEPG1 in the yeast two-hybrid system. The interaction was further confirmed by bimolecular fluorescence complementation and luciferase complementation imaging assays in N. benthamiana leaves. GhOPR9 plays a positive role in the resistance of cotton to V. dahliae by regulating JA biosynthesis. These results indicate that VdEPG1 may be able to regulate host immune responses as a virulence factor through modulating the GhOPR9-mediated JA biosynthesis.

Topics: Ascomycota; Disease Resistance; Gene Expression Regulation, Plant; Glycoside Hydrolases; Gossypium; Plant Diseases; Verticillium; Virulence Factors

Verticillium dahliae, one of the most destructive fungal pathogens of several crops, challenges the sustainability of cotton productivity worldwide because very few widely-cultivated Upland cotton varieties are resistant to Verticillium wilt (VW). Here, we report that REVEILLE2 (RVE2), the Myb-like transcription factor, confers the novel function in resistance to VW by regulating the jasmonic acid (JA) pathway in cotton. RVE2 expression was essentially required for the activation of JA-mediated disease-resistance response. RVE2 physically interacted with TPL/TPRs and disturbed JAZ proteins to recruit TPL and TPR1 in NINJA-dependent manner, which regulated JA response by relieving inhibited-MYC2 activity. The MYC2 then bound to RVE2 promoter for the activation of its transcription, forming feedback loop. Interestingly, a unique truncated RVE2 widely existing in D-subgenome (GhRVE2D) of natural Upland cotton represses the ability of the MYC2 to activate GhRVE2A promoter but not GausRVE2 or GbRVE2. The result could partially explain why Gossypium barbadense popularly shows higher resistance than Gossypium hirsutum. Furthermore, disturbing the JA-signalling pathway resulted into the loss of RVE2-mediated disease-resistance in various plants (Arabidopsis, tobacco and cotton). RVE2 overexpression significantly enhanced the resistance to VW. Collectively, we conclude that RVE2, a new regulatory factor, plays a pivotal role in fine-tuning JA-signalling, which would improve our understanding the mechanisms underlying the resistance to VW.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Oxylipins; Plant Diseases; Plant Proteins; Signal Transduction; Verticillium

Green leaf volatiles (GLVs), volatile organic compounds released by plants upon tissue damage, are key signaling molecules in plant immunity. The ability of exogenous GLV application to trigger an induced resistance (IR) phenotype against arthropod pests has been widely reported, but its effectiveness against plant pathogens is less well understood. In this study, we combined mRNA sequencing-based transcriptomics and phytohormone measurements with multispectral imaging-based precision phenotyping to gain insights into the molecular basis of Z-3-hexenyl acetate-induced resistance (Z-3-HAC-IR) in rice. Furthermore, we evaluated the efficacy of Z-3-HAC-IR against a panel of economically significant rice pathogens: Pyricularia oryzae, Rhizoctonia solani, Xanthomonas oryzae pv. oryzae, Cochliobolus miyabeanus, and Meloidogyne graminicola. Our data revealed rapid induction of jasmonate metabolism and systemic induction of plant immune responses upon Z-3-HAC exposure, as well as a transient allocation cost due to accelerated chlorophyll degradation and nutrient remobilization. Z-3-HAC-IR proved effective against all tested pathogens except for C. miyabeanus, including against the (hemi)biotrophs M. graminicola, X. oryzae pv. oryzae, and P. oryzae. The Z-3-HAC-IR phenotype was lost in the jasmonate (JA)-deficient hebiba mutant, which confirms the causal role of JA in Z-3-HAC-IR. Together, our results show that GLV exposure in rice induces broad-spectrum, JA-mediated disease resistance with limited allocation costs, and may thus be a promising alternative crop protection approach.

Topics: Disease Resistance; Oryza; Plant Diseases; Plant Leaves; Xanthomonas

Wheat (Triticum aestivum) is one of the most essential human energy and protein sources. However, wheat production is threatened by devastating fungal diseases such as stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici (Pst). Here, we reveal that the alternations in chloroplast lipid profiles and the accumulation of jasmonate (JA) in the necrosis region activate JA signaling and trigger the host defense. The collapse of chloroplasts in the necrosis region results in accumulations of polyunsaturated membrane lipids and the lipid-derived phytohormone JA in transgenic lines of Yr36 that encodes Wheat Kinase START 1 (WKS1), a high-temperature-dependent adult plant resistance protein. WKS1.1, a protein encoded by a full-length splicing variant of WKS1, phosphorylates and enhances the activity of keto-acyl thiolase (KAT-2B), a critical enzyme catalyzing the β-oxidation reaction in JA biosynthesis. The premature stop mutant, kat-2b, accumulates less JA and shows defects in the host defense against Pst. Conversely, overexpression of KAT-2B results in a higher level of JA and limits the growth of Pst. Moreover, JA inhibits the growth and reduces pustule densities of Pst. This study illustrates the WKS1.1‒KAT-2B‒JA pathway for enhancing wheat defense against fungal pathogens to attenuate yield loss.

Topics: Basidiomycota; Disease Resistance; Humans; Lipids; Necrosis; Phosphorylation; Plant Diseases; Triticum

To explore the signal transmission mechanism of the arbuscular mycorrhizal network against root rot of Salvia miltiorrhiza. In this experiment, the arbuscular mycorrhizal hyphal network was established among Salvia miltiorrhiza plants, and a two plant three-compartment culture model was established. The root of the donor Salvia miltiorrhiza was inoculated with the pathogenic fungi Fusarium solani. The changes of hormone signals such as jasmonic acid and salicylic acid and the expression of related defense genes in the recipient Salvia miltiorrhiza plants in different periods were measured, to study the underground disease resistance signal transmission mechanism among medicinal plants. Salvia miltiorrhiza can transmit the signal of resistance to root rot through the jasmonic acid pathway; When plants suffer from disease stress, the content of JA increases significantly, and the increase of JA content will inhibit the content of SA in plants; The gene expression of PR-10 gene in the roots of Salvia miltiorrhiza with arbuscular mycorrhizal network infected by pathogenic fungi was 17.56 times higher than that inoculated only with pathogenic fungi; Changes in hormone content will also cause changes in the expression of related defense genes, such as SnRK2 is inhibited by ABA in the signal transduction pathway, while JA and ABA show antagonistic changes after inoculation of pathogenic fungi in Salvia miltiorrhiza, so JA may positively regulate the expression of SnRK2 gene. Plants can transmit signals through AM hyphal network after being stressed by the pathogen Fusarium solani. In the arbuscular mycorrhizal hyphal network, JA has important significance for the signal transmission of resistance to root rot and disease resistance of Salvia miltiorrhiza, which can make Salvia miltiorrhiza ready for stress resistance and improve the stress resistance of Salvia miltiorrhiza. This experiment is of great significance to further analyze the signal transmission mechanism of the arbuscular mycorrhizal hyphal network.

Topics: Disease Resistance; Hormones; Mycorrhizae; Plant Roots; Salvia miltiorrhiza

Verticillium wilt of cotton is a very serious soil-borne disease and there is no effective control method. The mechanism of Gossypium hirsutum thaumatin-like protein 1(GhTLP1) in upland cotton regulating Verticillium wilt resistance has been an uncovered research approach. GhTLP1 is mainly localized in the cell wall. Overexpression of GhTLP1 significantly enhanced Arabidopsis plants resistance to Verticillium dahliae, while its homologous mutant tlp1 in Arabidopsis was more susceptible to the pathogen, and the heterologous complement line (EC) recovered resistance to V. dahliae. GhTLP1 responds to jasmonate acid (JA) and abscisic acid (ABA) hormones and regulates mitogen-activated protein kinase (MAPK) signaling pathway-plant pathway to enhance Arabidopsis plants resistance to V. dahliae. Silencing GhTLP1 resulted decrease in cotton plants resistance to V. dahliae. Moreover, the mutation of GhTLP1 at site Tyr97 and Tyr199 with the phosphorylation also decreased plant resistance to V. dahliae. Therefore, GhTLP1 phosphorylation was observed important in cotton plants against V. dahliae. Further analysis demonstrated that GhTLP1 interacted with gossypium hirsutum laccase 14 (GhLAC14) to enhance plants resistance to V. dahliae. Silencing GhLAC14 resulted decrease in cotton plants resistance to V. dahliae. Here, we propose that GhTLP1 is a potential molecular target for improving resistance to Verticillium wilt in cotton.

Topics: Abscisic Acid; Arabidopsis; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Plant Diseases; Plant Proteins; Signal Transduction; Verticillium

Brown spot disease (BSD) of rice (Oryza sativa L.) caused by Bipolaris oryzae is one of the major and neglected fungal diseases worldwide affecting rice production. Despite its significance, very limited knowledge on genetics and genomics of rice in response to B. oryzae available. Our study firstly identified moderately resistant (Gitesh) and susceptible (Shahsarang) North-East Indian rice cultivars in response to a native Bipolaris oryzae isolate BO1. Secondly, a systematic comparative RNA seq was performed for both cultivars at four different time points viz. 12, 24, 48, and 72 hours post infestation (hpi). Differential gene expression analysis revealed the importance of early response to the pathogen in suppressing disease progression. The pathogen negatively regulates the expression of photosynthetic-related genes at early stages in both cultivars. Of the cell wall modification enzymes, cellulose synthase and callose synthase are important for signal transduction and defense. Cell wall receptors OsLYP6, OsWAK80 might positively and OsWAK25 negatively regulate disease resistance. Jasmonic acid and/or abscisic acid signaling pathways are presumably involved in disease resistance, whereas salicylic acid pathway, and an ethylene response gene OsEBP-89 in promoting disease. Surprisingly, pathogenesis-related proteins showed no antimicrobial impact on the pathogen. Additionally, transcription factors OsWRKY62 and OsWRKY45 together might negatively regulate resistance to the pathogen. Taken together, our study has identified and provide key regulatory genes involved in response to B. oryzae which serve as potential resources for functional genetic analysis to develop genetic tolerance to BSD of rice.

Topics: Abscisic Acid; Bipolaris; Cell Wall; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Salicylic Acid; Signal Transduction; Transcription Factors

Trichoderma atroviride is a root-colonizing fungus that confers multiple benefits to plants. In plants, small RNA (sRNA)-mediated gene silencing (sRNA-MGS) plays pivotal roles in growth, development, and pathogen attack. Here, we explored the role of core components of Arabidopsis thaliana sRNA-MGS pathways during its interaction with Trichoderma. Upon interaction with Trichoderma, sRNA-MGS-related genes paralleled the expression of Arabidopsis defense-related genes, linked to salicylic acid (SA) and jasmonic acid (JA) pathways. SA- and JA-related genes were primed by Trichoderma in leaves after the application of the well-known pathogen-associated molecular patterns flg22 and chitin, respectively. Defense-related genes were primed in roots as well, but to different extents and behaviors. Phenotypical characterization of mutants in AGO genes and components of the RNA-dependent DNA methylation (RdDM) pathway revealed that different sets of sRNA-MGS-related genes are essential for (i) the induction of systemic acquired resistance against Botrytis cinerea, (ii) the activation of the expression of plant defense-related genes, and (iii) root colonization by Trichoderma. Additionally, plant growth induced by Trichoderma depends on functional RdDM. Profiling of DNA methylation and histone N-tail modification patterns at the Arabidopsis Nitrile-Specifier Protein-4 (NSP4) locus, which is responsive to Trichoderma, showed altered epigenetic modifications in RdDM mutants. Furthermore, NSP4 is required for the induction of systemic acquired resistance against Botrytis and avoidance of enhanced root colonization by Trichoderma. Together, our results indicate that RdDM is essential in Arabidopsis to establish a beneficial relationship with Trichoderma. We propose that DNA methylation and histone modifications are required for plant priming by the beneficial fungus against B. cinerea.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Hypocreales; Nitriles; Oxylipins; Plant Diseases; Plant Roots; RNA; Salicylic Acid; Trichoderma

Root rot of

Topics: Cyclopentanes; Disease Resistance; Fusarium; Nicotiana; Oxylipins; Panax notoginseng; Photosynthesis; Plant Diseases; Signal Transduction; Transcription Factors

Lesion mimic mutants (LMMs) have been widely used in experiments in recent years for studying plant physiological mechanisms underlying programmed cell death (PCD) and defense responses. Here, we identified a lesion mimic mutant,

Topics: Chloroplasts; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Mutation; Oryza; Oxylipins; Phenotype; Photosynthesis; Plant Diseases; UDPglucose 4-Epimerase

In plants, MYB transcription factors play diverse roles in growth, development, and response to abiotic and biotic stresses. However, the signaling processes of these transcription factors in defense against pathogen attacks remain largely unknown. This study isolated a novel R2R3-type MYB transcription factor GhODO1 from cotton (Gossypium hirsutum) and functionally characterized its positive role in tolerance to Verticillium dahliae. GhODO1 was induced by V. dahliae and jasmonic acid (JA) and transient expression of fused GhODO1-GFP in onion epidermal cells showed that GhODO1 protein was localized in the cell nucleus. Knockdown of GhODO1 significantly reduced the resistance of cotton to V. dahliae, whereas GhODO1 ectopic overexpression in Arabidopsis conferred enhanced resistance to V. dahliae. Lignin deposition was significantly decreased in GhODO1-silenced cotton plants after V. dahliae inoculation and mock treatment. The expression levels of genes and activities of enzymes involved in lignin biosynthesis were reduced in GhODO1-silenced cotton plants compared to the TRV:00. Yeast one-hybrid assays revealed that GhODO1 protein interacts with the promoters of lignin biosynthesis-related genes Gh4CL1 and GhCAD3, directly activates their expression, and enhances total lignin accumulation. Moreover, GhODO1 silencing compromised JA-mediated defense signaling and JA accumulation. These results show that GhODO1 is involved in cotton resistance to V. dahliae by involving the lignin biosynthesis and the JA signaling pathway.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Lignin; Oxylipins; Plant Diseases; Plant Proteins; Signal Transduction; Transcription Factors; Verticillium

Plant hormones regulate growth, development, and defense against biotic and abiotic stresses. Salicylic acid (SA), ethylene (ET), and jasmonate (JA) are major phytohormones that control the defense against pathogens. SA and JA primarily regulate resistance against biotrophic and necrotrophic pathogens, respectively. NPR1 is the key regulator of SA signaling in plants. AtOZF1 function has recently been ascribed to promote both NPR1- dependent and -independent SA signaling. However, the role of AtOZF1 in JA signaling was not known. Here we report AtOZF1 as a positive regulator of JA signaling in Arabidopsis. The

Topics: Acetates; Antimicrobial Cationic Peptides; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Defensins; Disease Resistance; Gene Expression Regulation, Plant; Membrane Proteins; Mutation; Oxylipins; Plant Diseases; Plant Growth Regulators; Salicylic Acid; Signal Transduction

Jasmonate induced FaTPS1 to produce terpene, and overexpression FaTPS1 led to fruit resistant against B. cinerea infection, FaMYC2 induced FaTPS1 by binding to its promoter that downstream of jasmonate. Jasmonic acid (JA) and its derivatives are associated with plant defence responses against pathogenic organisms. In the present study, a total of 10,631 differentially expressed genes, 239 differentially expressed proteins, and 229 differential metabolites were screened and found to be mainly involved in pathogen perception, hormone biosynthesis and signal transduction, photosynthesis, and secondary metabolism. In strawberry fruits, methyl jasmonate (MeJA) induced FaTPS1 expression and quickly increased the terpene content. Furthermore, FaTPS1 overexpression increased the emission of sesquiterpenes, especially germacrene D, and improved strawberry resistance against Botrytis cinerea infection, although the knockdown of FaTPS1 increased its susceptibility to the same pathogen. Using a yeast one-hybrid assay and transient expression analysis, we demonstrated that FaMYC2 can bind to the G-box element in the promoter region of FaTPS1, thus inducing FaTPS1 expression. MeJA also stimulated FaMYC2 expression and regulated downstream signalling cascades. Moreover, we presented a possible model of the new signalling pathway of MeJA-mediated strawberry resistance to B. cinerea.

Topics: Alkyl and Aryl Transferases; Botrytis; Cyclopentanes; Disease Resistance; Fragaria; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Proteins; Terpenes

SQUINT (SQN) regulates plant maturation by promoting the activity of miR156, which functions primarily in the miR156-SQUAMOSA PROMOTER BINDING PROTEIN-LIKE9 (SPL9) module regulating plant growth and development. Here, we show that SQN acts in the jasmonate (JA) pathway, a major signaling pathway regulating plant responses to insect herbivory and pathogen infection. Arabidopsis thaliana sqn mutants showed elevated sensitivity to the necrotrophic fungus Botrytis cinerea compared with wild type. However, SQN is not involved in the early pattern-triggered immunity response often triggered by fungal attack. Rather, SQN positively regulates the JA pathway, as sqn loss-of-function mutants treated with B. cinerea showed reduced JA accumulation, JA response and sensitivity to JA. Furthermore, the miR156-SPL9 module regulates plant resistance to B. cinerea: mir156 mutant, and SPL9 overexpression plants displayed elevated sensitivity to B. cinerea. Moreover, constitutively expressing miR156a or reducing SPL9 expression in the sqn-1 mutant restored the sensitivity of Arabidopsis to B. cinerea and JA responses. These results suggest that SQN positively modulates plant resistance to B. cinerea through the JA pathway, and the miR156-SPL9 module functions as a bridge between SQN and JA to mediate plant resistance to this pathogen.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; MicroRNAs; Oxylipins; Plant Diseases; Strabismus; Trans-Activators

Topics: Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Indoles; Oxylipins; Plant Diseases; Signal Transduction; Thiazoles

Botrytis cinerea is one of the most widely distributed and harmful pathogens worldwide. Both the phytohormone jasmonate (JA) and the VQ motif-containing proteins play crucial roles in plant resistance to B. cinerea. However, their crosstalk in resistance to B. cinerea is unclear, especially in tomato (Solanum lycopersicum). In this study, we found that the tomato VQ15 was highly induced upon B. cinerea infection and localized in the nucleus. Silencing SlVQ15 using virus-induced gene silencing reduced resistance to B. cinerea. Overexpression of SlVQ15 enhanced resistance to B. cinerea, while disruption of SlVQ15 using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein9 (Cas9) technology increased susceptibility to B. cinerea. Furthermore, SlVQ15 formed homodimers. Additionally, SlVQ15 interacted with JA-ZIM domain proteins, repressors of the JA signaling pathway, and SlWRKY31. SlJAZ11 interfered with the interaction between SlVQ15 and SlWRKY31 and repressed the SlVQ15-increased transcriptional activation activity of SlWRKY31. SlVQ15 and SlWRKY31 synergistically regulated tomato resistance to B. cinerea, as silencing SlVQ15 enhanced the sensitivity of slwrky31 to B. cinerea. Taken together, our findings showed that the SlJAZ-interacting protein SlVQ15 physically interacts with SlWRKY31 to cooperatively control JA-mediated plant defense against B. cinerea.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Proteins; Solanum lycopersicum

The annual yield losses caused by the Rice Blast Fungus, Magnaporthe oryzae, range to the equivalent for feeding 60 million people. To ward off infection by this fungus, rice has evolved a generic basal immunity (so called compatible interaction), which acts in concert with strain-specific defence (so-called incompatible interaction). The plant-defence hormone jasmonic acid (JA) promotes the resistance to M. oryzae, but the underlying mechanisms remain elusive. To get more insight into this open question, we employ the JA-deficient mutants, cpm2 and hebiba, and dissect the JA-dependent defence signalling in rice for both, compatible and incompatible interactions.. We observe that both JA-deficient mutants are more susceptible to M. oryzae as compared to their wild-type background, which holds true for both types of interactions as verified by cytological staining. Secondly, we observe that transcripts for JA biosynthesis (OsAOS2 and OsOPR7), JA signalling (OsJAZ8, OsJAZ9, OsJAZ11 and OsJAZ13), JA-dependent phytoalexin synthesis (OsNOMT), and JA-regulated defence-related genes, such as OsBBTI2 and OsPR1a, accumulate after fungal infection in a pattern that correlates with the amplitude of resistance. Thirdly, induction of defence transcripts is weaker during compatible interaction.. The study demonstrates the pivotal role of JA in basal immunity of rice in the resistance to M. oryzae in both, compatible and incompatible interactions.

Topics: Ascomycota; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Magnaporthe; Oryza; Plant Diseases

Terpinen-4-ol, the main component of tea tree oil, markedly increases the disease resistance of postharvest strawberry fruit. To understand the mechanism underlying the enhancement of disease resistance, a high-throughput RNA-seq was used to analyze gene transcription in terpinen-4-ol-treated and untreated fruit. The results show that terpinen-4-ol induces the expression of genes in the jasmonic acid (JA) biosynthesis pathway, secondary metabolic pathways such as phenylpropanoid biosynthesis, and pathways involved in plant-pathogen interactions. Terpinen-4-ol treatment reduced disease incidence and lesion diameter in strawberry fruit inoculated with

Topics: Botrytis; Cyclopentanes; Disease Resistance; Fragaria; Fruit; Oxylipins; Plant Diseases; Signal Transduction; Terpenes

The Mediator complex acts as a bridge between specific transcription factors and the RNA polymerase II transcriptional machinery and plays a central role in plant immunity. Biological induction of plant resistance against pathogens requires endogenous hormone jasmonic acid (JA) and involves profound transcriptional changes controlled by the key transcription factor MYC2. Arabidopsis thaliana Mediator subunit 25 (AtMED25) regulates JA-dependent defense response through interacting with MYC2. Here, we report that the tomato (Solanum lycopersicum, Sl) Mediator subunit 8 (SlMED8) is another essential component in JA-dependent defense response. The transcript levels of SlMED8 could not be affected by treatment with MeJA, SA, ABA, and mechanical wounding. Yeast two-hybrid assays showed that SlMED8 could interact with itself, SlMYC2, and SlMED25, respectively. In addition, ectopic overexpression of SlMED8 complemented the late flowering and pathogen hypersensitivity phenotypes of Arabidopsis med8 mutant. Overexpression of SlMED8 rendered transgenic plants higher tolerance to necrotrophic pathogen Botrytis cinerea. Meanwhile, SlMED8 antisense plants displayed compromised resistance to Botrytis cinerea. Consistent with this, differential expression levels of several JA-responsive genes were detected within the transgenic plants. Overall, our results identified an important control point in the regulation of the JA signaling pathway within the transcriptional machinery.

Topics: Arabidopsis; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plants, Genetically Modified; Solanum lycopersicum; Transcription Factors

Mitochondrial processes are implicated in plant response to biotic stress caused by viruses, actinomyces, bacteria and pests, but their function in defense against fungal invasion remains unclear. Here, we investigated the role and regulation of mitochondrial alternative oxidase (AOX) in response to black spot disease caused by the hemibiotrophic fungus Marssonina brunnea in poplar. M. brunnea inoculation induced the transcription of the AOX1a gene in the mitochondrial electron transport chain and of jasmonic acid (JA) and ethylene (ET) biosynthetic genes, with the accumulation of these phytohormones in poplar leaf, while inhibiting the transcript amount of the mitochondrial cytochrome c oxidase gene (COX6b) and genes related to salicylic acid (SA). Enhanced AOX reduced poplar susceptibility to M. brunnea with a higher ATP/ADP ratio while the repressed AOX caused the reverse effect. Exogenous JA and 1-aminocyclopropane-1-carboxylic acid (ACC, a biosynthetic precursor of ET) inhibited the transcript amount of COX6b and consequently increased the ratio of AOX pathway to total respiration. Furthermore, the transcription of CYS C1 and CYS D1 genes catalyzing cyanide metabolism was induced, while the cysteine (CYS) substrate levels reduced upon M. brunnea inoculation; exogenous JA and ACC mimicked the effect of M. brunnea infection on cysteine. Exogenous SA enhanced, while JA and ACC reduced, poplar susceptibility to M. brunnea. Moreover, inhibiting AOX completely prohibited JA- and ET-increased tolerance to M. brunnea in poplar. These observations indicate that the JA- and ET-induced mitochondrial AOX pathway triggers defense against M. brunnea in poplar. This effect probably involves cyanide. These findings deepen our understanding of plant-pathogenic fungi interactions.

Topics: Ascomycota; Cyclopentanes; Disease Resistance; Ethylenes; Mitochondrial Proteins; Oxidoreductases; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Populus

SlMYB75 increased the accumulation of JA and improved the scavenging of excess H

Topics: Botrytis; Catalase; Cell Wall; Cyclopentanes; Disease Resistance; Food Storage; Fruit; Gene Expression Regulation, Plant; Hydrogen Peroxide; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Reactive Oxygen Species; Solanum lycopersicum; Transcription Factors; Waxes

Living in natural environment, plants often suffer from various biotic and abiotic stresses. Phosphate deficiency is a common factor affecting crop production in field, while pathogen invasion is another serious problem. Here we report that Pi-deficient cotton plants exhibit enhanced resistance to Verticillium dahliae. Transcriptomic and histochemical analysis revealed that cotton phenylpropanoid pathway was activated under phosphate deficiency, including lignin and flavonoid biosynthesis. Metabolomic data showed that Pi-deficient cotton accumulates many flavonoids metabolites and displays obvious anti-fungi activity in terms of methanolic extract. Additionally, JA biosynthesis was activated under phosphate deficiency and the Pi-deficiency induced disease resistance was significantly attenuated in GhAOS knock down plants. Taken together, our study demonstrated that phosphate deficiency enhanced cotton resistance to V. dahliae through activating phenylpropanoid pathway and JA biosynthesis, providing new insights into how phosphate deficiency affects plant disease resistance.

Topics: Ascomycota; Cyclopentanes; Disease Resistance; Flavonoids; Gene Expression Profiling; Gossypium; Lignin; Metabolic Networks and Pathways; Oxylipins; Phosphates; Plant Diseases; Plant Growth Regulators

Overexpression of CiNPR4 enhanced resistance of transgenic citrus plants to Huanglongbing by perceiving the salicylic acid and jasmonic acid signals and up-regulating the transcriptional activities of plant-pathogen interaction genes. Developing transgenic citrus plants with enhanced immunity is an efficient strategy to control citrus Huanglongbing (HLB). Here, a nonexpressor of pathogenesis-related gene 1 (NPR1) like gene from HLB-tolerant 'Jackson' grapefruit (Citrus paradisi Macf.), CiNPR4, was introduced into 'Wanjincheng' orange (Citrus sinensis Obseck). CiNPR4 expression was determined in transgenic citrus plants using quantitative real-time PCR analyses. The Candidatus Liberibacter asiaticus (CLas) pathogen of HLB was successfully transmitted to transgenic citrus plants by grafting infected buds. HLB symptoms developed in transgenic and wild-type (WT) plants by 9 months after inoculation. A CLas population analysis showed that 26.9% of transgenic lines exhibited significantly lower CLas titer levels compared with the CLas-infected WT plants at 21 months after inoculation. Lower starch contents and anatomical aberration levels in the phloem were observed in transgenic lines having enhanced resistance compared with CLas-infected WT plants. CiNPR4 overexpression changed the jasmonic acid, but not salicylic acid, level. Additionally, the jasmonic acid and salicylic acid levels increased after CLas infection. Transcriptome analyses revealed that the enhanced resistance of transgenic plants to HLB resulted from the up-regulated transcriptional activities of plant-pathogen interaction-related genes.

Topics: Citrus paradisi; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Liberibacter; Oxylipins; Phloem; Phylogeny; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Reproducibility of Results; Salicylic Acid; Sequence Analysis, RNA; Starch

Fusarium yellows resistant and susceptible lines in Brassica rapa showed different salicylic acid responses; the resistant line showed a similar response to previous reports, but the susceptible line differed. Fusarium yellows caused by Fusarium oxysporum f. sp. conglutinans (Foc) is an important disease. Previous studies showed that genes related to salicylic acid (SA) response were more highly induced following Foc infection in Brassica rapa Fusarium yellows resistant lines than susceptible lines. However, SA-induced genes have not been identified at the whole genome level and it was unclear whether they were up-regulated by Foc inoculation. Transcriptome analysis with and without SA treatment in the B. rapa Fusarium yellows susceptible line 'Misugi' and the resistant line 'Nanane' was performed to obtain insights into the relationship between SA sensitivity/response and Fusarium yellows resistance. 'Nanane's up-regulated genes were related to SA response and down-regulated genes were related to jasmonic acid (JA) or ethylene (ET) response, but differentially expressed genes in 'Misugi' were not. This result suggests that Fusarium yellows resistant and susceptible lines have a different SA response and that an antagonistic transcription between SA and JA/ET responses was found only in a Fusarium yellows resistant line. SA-responsive genes were induced by Foc inoculation in Fusarium yellows resistant (RJKB-T23) and susceptible lines (RJKB-T24). By contrast, 39 SA-induced genes specific to RJKB-T23 might function in the defense response to Foc. In this study, SA-induced genes were identified at the whole genome level, and the possibility, the defense response to Foc observed in a resistant line could be mediated by SA-induced genes, is suggested. These results will be useful for future research concerning the SA importance in Foc or other diseases resistance in B. rapa.

Topics: Arabidopsis; Brassica rapa; Cyclopentanes; Disease Resistance; Ethylenes; Fusarium; Gene Expression Regulation, Plant; Gene Ontology; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Proteins; Reproducibility of Results; Salicylic Acid

Rhizoctonia solani causes damaging yield losses on most major food crops. R. solani isolates belonging to anastomosis group 8 (AG8) are soil-borne, root-infecting pathogens with a broad host range. AG8 isolates can cause disease on wheat, canola and legumes, however Arabidopsis thaliana is heretofore thought to possess non-host resistance as A. thaliana ecotypes, including the reference strain Col-0, are resistant to AG8 infection. Using a mitochondria-targeted redox sensor (mt-roGFP2) and cell death staining, we demonstrate that both AG8 and a host isolate (AG2-1) of R. solani are able to infect A. thaliana roots. Above ground tissue of A. thaliana was found to be resistant to AG8 but not AG2. Genetic analysis revealed that ethylene, jasmonate and PENETRATION2-mediated defense pathways work together to provide resistance to AG8 in the leaves which subsequently enable tolerance of root infections. Overall, we demonstrate a significant difference in defense capabilities of above and below ground tissue in providing resistance to R. solani AG8 in Arabidopsis.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Ethylenes; Host-Pathogen Interactions; Immunohistochemistry; N-Glycosyl Hydrolases; Oxylipins; Plant Diseases; Plant Roots; Rhizoctonia; Signal Transduction; Stress, Physiological

Verticillium wilt is a widespread and destructive disease, which causes serious loss of cotton yield and quality. Long non-coding RNA (lncRNA) is involved in many biological processes, such as plant disease resistance response, through a variety of regulatory mechanisms, but their possible roles in cotton against Verticillium dahliae infection remain largely unclear.. Here, we measured the transcriptome of resistant G. hirsutum following infection by V. dahliae and 4277 differentially expressed lncRNAs (delncRNAs) were identified. Localization and abundance analysis revealed that delncRNAs were biased distribution on chromosomes. We explored the dynamic characteristics of disease resistance related lncRNAs in chromosome distribution, induced expression profiles, biological function, and these lncRNAs were divided into three categories according to their induced expression profiles. For the delncRNAs, 687 cis-acting pairs and 14,600 trans-acting pairs of lncRNA-mRNA were identified, which indicated that trans-acting was the main way of Verticillium wilt resistance-associated lncRNAs regulating target mRNAs in cotton. Analyzing the regulation pattern of delncRNAs revealed that cis-acting and trans-acting lncRNAs had different ways to influence target genes. Gene Ontology (GO) enrichment analysis revealed that the regulatory function of delncRNAs participated significantly in stimulus response process, kinase activity and plasma membrane components. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that delncRNAs participated in some important disease resistance pathways, such as plant-pathogen interaction, alpha-linolenic acid metabolism and plant hormone signal transduction. Additionally, 21 delncRNAs and 10 target genes were identified as being involved in alpha-linolenic acid metabolism associated with the biosynthesis of jasmonic acid (JA). Subsequently, we found that GhlncLOX3 might regulate resistance to V. dahliae through modulating the expression of GhLOX3 implicated in JA biosynthesis. Further functional analysis showed that GhlncLOX3-silenced seedlings displayed a reduced resistance to V. dahliae, with down-regulated expression of GhLOX3 and decreased content of JA.. This study shows the dynamic characteristics of delncRNAs in multiaspect, and suggests that GhlncLOX3-GhLOX3-JA network participates in response to V. dahliae invasion. Our results provide novel insights for genetic improvement of Verticillium wilt resistance in cotton using lncRNAs.

Topics: Base Sequence; Chromosomes, Plant; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Gossypium; Oxylipins; Plant Diseases; Plant Proteins; Plant Roots; RNA, Long Noncoding; RNA, Messenger; Time Factors; Verticillium

APETALA2/ethylene responsive factor (AP2/ERF) transcription factors are a plant-specific family of transcription factors and one of the largest families of transcription factors. Ethylene response factors (ERF) regulate plant growth, development, and responses to biotic and abiotic stress. In a previous study, the ERF2 gene was significantly upregulated in both resistant and susceptible tomato cultivars in response to Stemphylium lycopersici. The main purpose of this study was to systematically analyze the ERF family and to explore the mechanism of ERF2 in tomato plants resisting pathogen infection by the Virus-induced Gene Silencing technique.. In this experiment, 134 ERF genes were explored and subjected to bioinformatic analysis and divided into twelve groups. The spatiotemporal expression characteristics of ERF transcription factor gene family in tomato were diverse. Combined with RNA-seq, we found that the expression of 18 ERF transcription factors increased after inoculation with S. lycopersici. In ERF2-silenced plants, the susceptible phenotype was observed after inoculation with S. lycopersici. The hypersensitive response and ROS production were decreased in the ERF2-silenced plants. Physiological analyses showed that the superoxide dismutase, peroxidase and catalase activities were lower in ERF2-silenced plants than in control plants, and the SA and JA contents were lower in ERF2-silenced plants than in control plants after inoculation with S. lycopersici. Furthermore, the results indicated that ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance.. In this study, we identified and analyzed members of the tomato ERF family by bioinformatics methods and classified, described and analyzed these genes. Subsequently, we used VIGS technology to significantly reduce the expression of ERF2 in tomatoes. The results showed that ERF2 had a positive effect on tomato resistance to S. lycopersici. Interestingly, ERF2 played a key role in multiple SA, JA and ROS signaling pathways to confer resistance to invasion by S. lycopersici. In addition, ERF2 may directly or indirectly regulate Pto, PR1b1 and PR-P2 expression and enhance tomato resistance to S. lycopersici. In summary, this study provides gene resources for breeding for disease resistance in tomato.

Topics: Amino Acid Motifs; Ascomycota; Catalase; Chromosomes, Plant; Conserved Sequence; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genome, Plant; Hydrogen Peroxide; Multigene Family; Organ Specificity; Oxylipins; Peroxidase; Phylogeny; Plant Diseases; Plant Proteins; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Superoxide Dismutase; Superoxides; Transcription Factors

Topics: Adaptation, Physiological; Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation; Hemiptera; Host-Pathogen Interactions; Insect Proteins; Models, Genetic; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plants; Signal Transduction

Topics: Alternaria; Cyclopentanes; Disease Resistance; Endo-1,4-beta Xylanases; Fungal Proteins; Fusarium; Gene Expression Regulation, Fungal; Hypocreales; Indoleacetic Acids; Oxylipins; Plant Diseases; Plant Proteins; Populus; Rhizoctonia

Phosphate (Pi) and MYC2-mediated jasmonate (JA) pathway play critical roles in plant growth and development. In particular, crosstalk between JA and Pi starvation signalling has been reported to mediate insect herbivory resistance in dicot plants. However, its roles and mechanism in monocot-bacterial defense systems remain obscure. Here, we report that Pi starvation in rice activates the OsMYC2 signalling and enhances resistance to Xanthomonas oryzae pv. oryzae (Xoo) infection. The direct regulation of OsPHR2 on the OsMYC2 promoter was confirmed by yeast one-hybrid, electrophoretic mobility shift, dual-luciferase and chromatin immunoprecipitation assays. Molecular analyses and infection studies using OsPHR2-Ov1 and phr2 mutants further demonstrated that OsPHR2 enhances antibacterial resistance via transcriptional regulation of OsMYC2 expression, indicating a positive role of OsPHR2-OsMYC2 crosstalk in modulating the OsMYC2 signalling and Xoo infection. Genetic analysis and infection assays using myc2 mutants revealed that Pi starvation-induced OsMYC2 signalling activation and consequent Xoo resistance depends on the regulation of OsMYC2. Together, these results reveal a clear interlink between Pi starvation- and OsMYC2- signalling in monocot plants, and provide new insight into how plants balance growth and defence by integrating nutrient deficiency and phytohormone signalling. We highlighted a molecular link connecting OsMYC2-mediated JA pathway and phosphate starvation signalling in monocot plant. We demonstrated that phosphate starvation promoted OsMYC2 signalling to enhance rice defence to bacterial blight via transcriptional regulation of OsPHR2 on OsMYC2.

Topics: Cyclopentanes; Disease Resistance; Oryza; Oxylipins; Phosphorus; Plant Diseases; Plant Proteins; Signal Transduction; Xanthomonas

Grapevine downy mildew, caused by the biotrophic oomycete

Topics: Biosynthetic Pathways; Chloroplasts; Cyclopentanes; Disease Resistance; Fatty Acid Desaturases; Gene Expression Regulation, Plant; Genotype; Lipids; Oomycetes; Oxylipins; Peronospora; Plant Diseases; Plant Leaves; Vitis

WRKY, as one of the largest families of transcription factors (TFs), binds to cis-acting elements of downstream genes to regulate biotic and abiotic stress. However, the role of SlWRKY46 in fungal disease response induced by Botrytis cinerea (B.cinerea) and potential mechanism remains obscure. To ascertain the role of SlWRKY46 in response to B.cinerea, we constructed SlWRKY46-overexpression plants, which were then inoculated with B.cinerea. SlWRKY46-overexpression plants were more susceptible to B.cinerea and accompanied by the inhibited activities of phenylalanine ammonialyase (PAL), polyphenol oxidase (PPO), chitinase (CHI), and β-1,3-glucanase (GLU). Additionally, SlWRKY46-overexpression plants showed the decreased activities of ascorbate peroxidase (APX), superoxide dismutase (SOD) and the content of H

Topics: Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Homeostasis; Hydrogen Peroxide; Oxylipins; Plant Diseases; Plant Proteins; Reactive Oxygen Species; Salicylic Acid; Solanum lycopersicum

Bacterial leaf streak (BLS) is a major bacterial disease of rice. Utilization of host genetic resistance has become one of the most important strategies for controlling BLS. However, only a few resistance genes have been characterized. Previously, a recessive BLS resistance gene bls1 was roughly mapped on chromosome 6. Here, we further delineated bls1 to a 21 kb region spanning four genes. Genetic analysis confirmed that the gene encoding a mitogen-activated protein kinase (OsMAPK6) is the target of the allelic genes BLS1 and bls1. Overexpression of BLS1 weakened resistance to the specific Xanthomonas oryzae pv. oryzicola (Xoc) strain JZ-8, while low expression of bls1 increased resistance. However, both overexpression of BLS1 and low expression of bls1 could increase no-race-specific broad-spectrum resistance. These results indicate that BLS1 and bls1 negatively regulate race-specific resistance to Xoc strain JZ-8 but positively and negatively control broad-spectrum resistance, respectively. Subcellular localization demonstrated that OsMAPK6 was localized in the nucleus. RGA4, which is known to mediate resistance to Xoc, is the potential target of OsMAPK6. Overexpression of BLS1 and low expression of bls1 showed increase in salicylic acid and induced expression of defense-related genes, simultaneously increasing broad-spectrum resistance. Moreover, low expression of bls1 showed increase an in jasmonic acid and abscisic acid, in company with an increase in resistance to Xoc strain JZ-8. Collectively, our study provides new insights into the understanding of BLS resistance and facilitates the development of rice host-resistant cultivars.

Topics: Abscisic Acid; Chromosome Mapping; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Mitogen-Activated Protein Kinase 6; Mutation; Oryza; Oxylipins; Phylogeny; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Xanthomonas

Mildew severely reduces soybean yield and quality, and pods are the first line of defence against pathogens. Maize-soybean intercropping (MSI) reduces mildew incidence on soybean pods; however, the mechanism remains unclear. Changing light (CL) from maize shading is the most important environmental feature in MSI. We hypothesized that CL affects isoflavone accumulation in soybean pods, affecting their disease resistance. In the present study, shading treatments were applied to soybean plants during different developmental stages according to various CL environments under MSI. Chlorophyll fluorescence imaging (CFI) and classical evaluation methods confirmed that CL, especially vegetative stage shading (VS), enhanced pod resistance to mildew. Further metabolomic analyses and exogenous jasmonic acid (JA) and biosynthesis inhibitor experiments revealed the important relationship between JA and isoflavone biosynthesis, which had a synergistic effect on the enhanced resistance of CL-treated pods to mildew. VS promoted the biosynthesis and accumulation of constitutive isoflavones upstream of the isoflavone pathway, such as aglycones and glycosides, in soybean pods. When mildew infects pods, endogenous JA signalling stimulated the biosynthesis of downstream inducible malonyl isoflavone (MIF) and glyceollin to improve pod resistance.

Topics: Acetates; Chromatography, High Pressure Liquid; Cyclopentanes; Disease Resistance; Fusarium; Gene Expression Regulation, Plant; Glycine max; Isoflavones; Light; Lipoxygenase Inhibitors; Metabolomics; Oxylipins; Plant Diseases; Pyrazoles; Real-Time Polymerase Chain Reaction; Soybean Proteins; Tandem Mass Spectrometry

Verticillium wilt is a major limiting factor for sustainable production of cotton but the mechanism of controlling this disease is still poorly understood. Lipoxygenase (LOX)-derived oxylipins have been implicated in defense responses against diverse pathogens; however there is limited information about the functional characterization of LOXs in response to Verticillium dahliae infection. In this study, we report the characterization of a cotton LOX gene, GhLOX2, which phylogenetically clustered into 13-LOX subfamily and is closely related to Arabidopsis LOX2 gene. GhLOX2 was predominantly expressed in leaves and strongly induced following V. dahliae inoculation and treatment of methyl jasmonate (MeJA). RNAi-mediated knock-down of GhLOX2 enhanced cotton susceptibility to V. dahliae and was coupled with suppression of jasmonic acid (JA)-related genes both after inoculation with the cotton defoliating strain V991 or MeJA treatment. Interestingly, lignin contents, transcripts of lignin synthesis genes and H

Topics: Amino Acid Sequence; Ascomycota; Cyclopentanes; Disease Resistance; Gene Knockdown Techniques; Gossypium; Lignin; Lipoxygenase; Metabolic Networks and Pathways; Oxylipins; Phylogeny; Plant Diseases; RNA Interference

MiR394 plays a negative role in tomato resistance to late blight. The lncRNA40787 severing as an eTM for miR394 to regulate LCR and exerting functions in tomato resistance. Tomato (Solanum lycopersicum), which was used as model species for studying the mechanism of plant disease defense, is susceptible to multiple pathogens. Non-coding RNA (ncRNA) has a pivotal role in plants response to biological stresses. It has previously been observed that the expression level of miR394 changed significantly after the infection of various pathogens. However, there has been no detailed investigation of the accumulated or suppressed mechanism of miR394. Our previous study predicted three lncRNAs (lncRNA40787, lncRNA27177, and lncRNA42566) that contain miR394 endogenous target mimics (eTM), which may exist as the competitive endogenous RNAs (ceRNAs) of miR394. In our study, the transcription levels of these three lncRNAs were strongly up-regulated in tomato upon infection with P. infestans. In contrast with the three lncRNAs, the accumulation of miR394 was significantly suppressed. Based on the expression pattern, and value of minimum free energy (mfes) that represents the binding ability between lncRNA and miRNA, lncRNA40787 was chosen for further investigation. Results showed that overexpression of lncRNA40787 reduced the expression of miR394 along with decreased lesion area and enhanced disease resistance. Overexpression of miR394, however, decreased the expression of its target gene Leaf Curling Responsiveness (LCR), and suppressed the synthesis components genes of jasmonic acid (JA), depressing the resistance of tomato to P. infestans infection. Taken together, our findings indicated that miR394 can be decoyed by lncRNA40787, and negatively regulated the expression of LCR to enhance tomato susceptibility under P. infestans infection. Our study provided detailed information on the lncRNA40787-miR394-LCR regulatory network and serves as a reference for future research.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Host-Pathogen Interactions; MicroRNAs; Oxylipins; Phytophthora infestans; Plant Diseases; Plant Proteins; RNA, Long Noncoding; RNA, Plant; Solanum lycopersicum

Xylogen-like proteins (XYLPs) are essential for plant growth, development, and stress responses. However, little is known about the XYLP gene family in grape and its protective effects against gray mold a destructive disease caused by

Topics: Arabidopsis; Biological Evolution; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Genome, Plant; Oxylipins; Plant Diseases; Plant Proteins; Signal Transduction; Vitis

Dendrobium catenatum belongs to the Orchidaceae, and is a precious Chinese herbal medicine. In the past 20 years, D. catenatum industry has developed from an endangered medicinal plant to multi-billion dollar grade industry. The necrotrophic pathogen Sclerotium delphinii has a devastating effection on over 500 plant species, especially resulting in widespread infection and severe yield loss in the process of large-scale cultivation of D. catenatum. It has been widely reported that Jasmonate (JA) is involved in plant immunity to pathogens, but the mechanisms of JA-induced plant resistance to S. delphinii are unclear.. In the present study, the role of JA in enhancing D. catenatum resistance to S. delphinii was investigated. We identified 2 COI1, 13 JAZ, and 12 MYC proteins in D. catenatum genome. Subsequently, systematic analyses containing phylogenetic relationship, gene structure, protein domain, and motif architecture of core JA pathway proteins were conducted in D. catenatum and the newly characterized homologs from its closely related orchid species Phalaenopsis equestris and Apostasia shenzhenica, along with the well-investigated homologs from Arabidopsis thaliana and Oryza sativa. Public RNA-seq data were investigated to analyze the expression patterns of D. catenatum core JA pathway genes in various tissues and organs. Transcriptome analysis of MeJA and S. delphinii treatment showed exogenous MeJA changed most of the expression of the above genes, and several key members, including DcJAZ1/2/5 and DcMYC2b, are involved in enhancing defense ability to S. delphinii in D. catenatum.. The findings indicate exogenous MeJA treatment affects the expression level of DcJAZ1/2/5 and DcMYC2b, thereby enhancing D. catenatum resistance to S. delphinii. This research would be helpful for future functional identification of core JA pathway genes involved in breeding for disease resistance in D. catenatum.

Topics: Acetates; Basidiomycota; Cyclopentanes; Dendrobium; Disease Resistance; Gene Expression Regulation, Plant; Multigene Family; Oxylipins; Phylogeny; Plant Diseases; Plant Immunity; Plant Proteins; Signal Transduction

Topics: Amino Acid Substitution; Animals; Anthocyanins; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Flowers; Gene Expression Regulation, Plant; Herbivory; Oxylipins; Plant Diseases; Plants, Genetically Modified; SKP Cullin F-Box Protein Ligases; Spodoptera; Suppression, Genetic

Plant defence is multilayered and is essential for surviving in a changing environment. The discovery of long noncoding RNAs (lncRNAs) has dramatically extended our understanding of post-transcriptional gene regulation in diverse biological processes. However, the expression profile and function of lncRNAs in disease resistance are still largely unknown, especially in monocots. Here, we performed strand-specific RNA sequencing of rice leaves infected by Xanthomonas oryzae pv. Oryzae (Xoo) in different time courses and systematically identified 567 disease-responsive rice lncRNAs. Target analyses of these lncRNAs showed that jasmonate (JA) pathway was significantly enriched. To reveal the interaction between lncRNAs and JA-related genes, we studied the coexpression of them and found 39 JA-related protein-coding genes to be interplayed with 73 lncRNAs, highlighting the potential modulation of lncRNAs in JA pathway. We subsequently identified an lncRNA, ALEX1, whose expression is highly induced by Xoo infection. A T-DNA insertion line constructed using enhancer trap system showed a higher expression of ALEX1 and exerted a significant resistance to rice bacterial blight. Functional study revealed that JA signalling is activated and the endogenous content of JA and JA-Ile is increased. Overexpressing ALEX1 in rice further confirmed the activation of JA pathway and resistance to bacterial blight. Our findings reveal the expression of pathogen-responsive lncRNAs in rice and provide novel insights into the connection between lncRNAs and JA pathway in the regulation of plant disease resistance.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Proteins; RNA, Long Noncoding; Xanthomonas

Multiple long-distance signals have been identified for pathogen-induced systemic acquired resistance, but mobile signals for symbiont-induced systemic resistance (ISR) are less well understood. We used ISR-positive and -negative mutants of maize (

Topics: Cyclopentanes; Disease Resistance; Fatty Acids, Unsaturated; Gene Expression Regulation, Plant; Isomerism; Lipoxygenase; Oxylipins; Plant Diseases; Trichoderma; Xylem; Zea mays

Plants have evolved powerful immune systems to recognize pathogens and avoid invasions, but the genetic basis of plant susceptibility is less well-studied, especially to oomycetes, which cause disastrous diseases in many ornamental plants and food crops. In this research, we identified a negative regulator of plant immunity to the oomycete Phytophthora parasitica, AtRTP5 (Arabidopsis thaliana Resistant to Phytophthora 5), which encodes a WD40 repeat domain-containing protein. The AtRTP5 protein, which was tagged with green fluorescent protein (GFP), is localized in the nucleus and plasma membrane. Both the A. thaliana T-DNA insertion rtp5 mutants and the Nicotiana benthamiana RTP5 (NbRTP5) silencing plants showed enhanced resistance to P. parasitica, while overexpression of AtRTP5 rendered plants more susceptible. The transcriptomic analysis showed that mutation of AtRTP5 suppressed the biosynthesis of endogenous jasmonic acid (JA) and JA-dependent responses. In contrast, salicylic acid (SA) biosynthesis and SA-dependent responses were activated in the T-DNA insertion mutant rtp5-3. These results show that AtRTP5 acts as a conserved negative regulator of plant immunity to Phytophthora pathogens by interfering with JA and SA signalling pathways.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; DNA, Bacterial; Mutation; Oxylipins; Phytophthora; Plant Diseases; Salicylic Acid; Transcription, Genetic

DEK involves in the modulation of cell proliferation, differentiation, apoptosis, migration and cell senescence. However, direct genetic evidence proving the functions of DEK in disease resistance against pathogens is still deficient. In the present study, four DEKs were identified in tomato genome and their roles in disease resistance in tomato were analyzed. The expression levels of DEKs were differently induced by Botrytis cinerea, Pseudomonas syringae pv. tomato (Pst) DC3000 and defense-related signaling molecules (such as jasmonic acid, aethylene precursor and salicylic acid). The DEKs' silencing by virus induced gene silencing led to decreased resistance against B. cinerea or Pst DC3000. The underlying mechanisms may be through the upregulation of the accumulation of reactive oxygen species (ROS) and the changed expression levels of defense-related genes by pathogen inoculation. These results indicate that DEKs involve in disease resistance against different pathogens and thus broaden the knowledge of DEK genes' function in tomato.

Topics: Botrytis; Chromosomal Proteins, Non-Histone; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Poly-ADP-Ribose Binding Proteins; Pseudomonas syringae; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Transcription Factors

Jasmonates are essential engineers of plant defense responses against many pests, including herbivorous insects. Herbivory induces the production of jasmonic acid (JA) and its bioactive conjugate jasmonoyl-L-isoleucine (JA-Ile), which then triggers a large transcriptional reprogramming to promote plant acclimation. The contribution of the JA pathway, including its components and regulators, to defense responses against insect herbivory can be evaluated by conducting bioassays with a wide range of host plants and insect pests. Here, we describe a detailed and reproducible protocol for testing feeding behavior of the generalist herbivore Spodoptera littoralis on the model plant Arabidopsis thaliana and hence infer the contribution of JA-mediated plant defense responses to a chewing insect.

Topics: Animals; Arabidopsis; Biological Assay; Cyclopentanes; Disease Resistance; Herbivory; Host-Parasite Interactions; Oxylipins; Phenotype; Spodoptera

Thrips are tiny, cell-content-feeding insects that are a major pest on crops and ornamentals. Besides causing direct feeding damage, thrips may also cause indirect damage by vectoring tospoviruses. Novel resistance mechanisms to thrips need to be discovered and validated. Induction of jasmonic acid-dependent defenses has been demonstrated to be essential for resistance to thrips, but underlying mechanisms still need to be discovered. For this, it is vital to use robust plant-thrips assays to analyze plant defense responses and thrips performance. In recently developed high-throughput phenotyping platforms, the feeding damage that is visible as silver spots, and the preference of thrips in a two-choice setup is assessed, using leaf discs. Here, we describe whole-plant thrips assays that are essential for (1) validation of findings obtained by the leaf disc assays, (2) assessment of longer-term effects on thrips feeding success and fecundity, (3) determination of spatial-temporal effects induced by primary thrips infestation on a secondary attack by thrips or other insects or pathogens, and (4) assessment of gene expression and metabolite changes. We present detailed methods and tips and tricks for (a) rearing and selection of thrips at different developmental stages, (b) treatment of the whole plant or an individual leaf with thrips, and (c) determination of feeding damage and visualization of thrips oviposition success in leaves.

Topics: Animals; Arabidopsis; Biological Assay; Cyclopentanes; Disease Resistance; Herbivory; Host-Parasite Interactions; Oxylipins; Phenotype; Plant Diseases; Plant Immunity; Plants; Thysanoptera

Symbiotic association of plants with arbuscular mycorrhizal (AM) fungi brings about changes in levels of the phytohormone jasmonate (JA) in root and shoot tissues of a plant. The enhanced JA levels not only play a role in controlling the extent of AM colonization but are also involved in the expression of mycorrhizal-induced resistance (MIR) against pathogens. We describe a method used to study the levels of a volatile jasmonate derivative, methyl jasmonate (MeJA), in tomato plants colonized by AM fungi and in response to subsequent attack by the foliar pathogen Alternaria alternata.

Topics: Acetates; Chromatography, Gas; Cyclopentanes; Disease Resistance; Fungi; Host-Pathogen Interactions; Mycorrhizae; Oxylipins; Plant Growth Regulators; Plant Roots; Symbiosis

ZmMYC2 was identified as the key regulator of JA signaling in maize and exhibited diverse functions through binding to many gene promoters as well as enhanced JA signaling in transgenic Arabidopsis. The plant hormone jasmonate (JA) extensively coordinates plant growth, development and defensive responses. MYC2 is the master regulator of JA signaling and has been widely studied in many plant species. However, little is known about this transcription factor in maize. Here, we identified one maize transcription factor with amino acid identity of 47% to the well-studied Arabidopsis AtMYC2, named as ZmMYC2. Gene expression analysis demonstrated inducible expression patterns of ZmMYC2 in response to multiple plant hormone treatments, as well as biotic and abiotic stresses. The yeast two-hybrid assay indicated physical interaction among ZmMYC2 and JA signal repressors ZmJAZ14, ZmJAZ17, AtJAZ1 and AtJAZ9. ZmMYC2 overexpression in Arabidopsis myc2myc3myc4 restored the sensitivity to JA treatment, resulting in shorter root growth and inducible anthocyanin accumulation. Furthermore, overexpression of ZmMYC2 in Arabidopsis elevated resistance to Botrytis cinerea. Further ChIP-Seq analysis revealed diverse regulatory roles of ZmMYC2 in maize, especially in the signaling crosstalk between JA and auxin. Hence, we identified ZmMYC2 and characterized its roles in regulating JA-mediated growth, development and defense responses.

Topics: Anthocyanins; Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Sequence Alignment; Sequence Analysis, Protein; Signal Transduction; Transcription Factors; Transcriptome; Two-Hybrid System Techniques; Zea mays

The conversion of oleic acid (C18:1) to linoleic acid (C18:2) in the endoplasmic reticulum is critical to the accumulation of polyunsaturated fatty acids in seeds and other tissues, and this reaction is catalyzed by a Δ12-desaturase, FATTY ACID DESATURASE2 (FAD2). Here, we report that the tomato (

Topics: Animals; Aphids; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Fatty Acid Desaturases; Fatty Acids; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation, Plant; Gene Ontology; Gene Silencing; Microtubule-Associated Proteins; Oxylipins; Phylogeny; Promoter Regions, Genetic; Sequence Homology, Amino Acid; Solanum lycopersicum; Stress, Physiological; Transcriptome

Disease resistance is an important factor that impacts rice production. However, the mechanisms underlying rice disease resistance remain to be elucidated.. Here, we show that a robust set of genes has been defined in rice response to the infections of Xanthomonas oryzae pv. oryzae (Xoo) and Magnaporthe oryzae (Mor). We conducted a comprehensive analysis of the available microarray data from a variety of rice samples with inoculation of Xoo and Mor. A set of 12,932 genes was identified to be regulated by Xoo and another set of 2709 Mor-regulated genes was determined. GO enrichment analysis of the regulated genes by Xoo or Mor suggested mitochondrion may be an arena for the up-regulated genes and chloroplast be another for the down-regulated genes by Xoo or Mor. Cytokinin-related processes were most frequently repressed by Xoo, while processes relevant to jasmonic acid and abscisic acid were most frequently activated by Xoo and Mor. Among genes responsive to Xoo and Mor, defense responses and diverse signaling pathways were the most frequently enriched resistance mechanisms. InterPro annotation showed the zinc finger domain family, WRKY proteins, and Myb domain proteins were the most significant transcription factors regulated by Xoo and Mor. KEGG analysis demonstrated pathways including 'phenylpropanoid biosynthesis', 'biosynthesis of antibiotics', 'phenylalanine metabolism', and 'biosynthesis of secondary metabolites' were most frequently triggered by Xoo and Mor, whereas 'circadian rhythm-plant' was the most frequent pathway repressed by Xoo and Mor.. The genes identified here represent a robust set of genes responsive to the infections of Xoo and Mor, which provides an overview of transcriptional reprogramming during rice defense against Xoo and Mor infections. Our study would be helpful in understanding the mechanisms of rice disease resistance.

Topics: Abscisic Acid; Anti-Bacterial Agents; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Magnaporthe; Oryza; Oxylipins; Phenylalanine; Plant Diseases; Signal Transduction; Transcription Factors; Xanthomonas

Salicylic acid (SA), an essential secondary messenger for plant defence responses, plays a role in maintaining a balance (trade-off) between plant growth and resistance induction, but the detailed mechanism has not been explored. Because the SA mimic benzothiadiazole (BTH) is a more stable inducer of plant defence than SA after exogenous application, we analysed expression profiles of defence genes after BTH treatment to better understand SA-mediated immune induction. Transcript levels of the salicylic acid glucosyltransferase (SAGT) gene were significantly lower in BTH-treated Nicotiana tabacum (Nt) plants than in SA-treated Nt control plants, suggesting that SAGT may play an important role in SA-related host defence responses. Treatment with BTH followed by SA suppressed SAGT transcription, indicating that the inhibitory effect of BTH is not reversible. In addition, in BTH-treated Nt and Nicotiana benthamiana (Nb) plants, an early high accumulation of SA and SA 2-O-β-d-glucoside was only transient compared to the control. This observation agreed well with the finding that SAGT-overexpressing (OE) Nb lines contained less SA and jasmonic acid (JA) than in the Nb plants. When inoculated with a virus, the OE Nb plants showed more severe symptoms and accumulated higher levels of virus, while resistance increased in SAGT-silenced (IR) Nb plants. In addition, the IR plants restricted bacterial spread to the inoculated leaves. After the BTH treatment, OE Nb plants were slightly larger than the Nb plants. These results together indicate that SAGT has a pivotal role in the balance between plant growth and SA/JA-mediated defence for optimum plant fitness.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucosyltransferases; Nicotiana; Oxylipins; Plant Diseases; Plant Leaves; Salicylic Acid; Thiadiazoles

Our previous study indicated that glycerol application induced resistance to powdery mildew (

Topics: Ascomycota; Cyclopentanes; Disease Resistance; Fatty Acids; Gene Expression Profiling; Glycerol; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Salicylic Acid; Triticum

In plants, enhanced defense often compromises growth and development, which is regarded as trade-offs between growth and defense. Here we identified a gene,

Topics: Aldehyde Dehydrogenase; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Magnaporthe; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Salicylic Acid

Cultivated sweet potato (

Topics: Acetates; Base Sequence; Cyclopentanes; Disease Resistance; DNA, Plant; Fusarium; Gene Expression Regulation, Plant; Genome, Plant; Ipomoea batatas; Models, Biological; Nicotiana; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Promoter Regions, Genetic; Protein Binding; Transcription, Genetic

Oxathiapiprolin was developed as a specific plant pathogenic oomycete inhibitor, previously shown to have highly curative and protective activities against the pepper Phytophthora blight disease under field and greenhouse tests. Therefore, it was hypothesized that oxathiapiprolin might potentially activate the plant disease resistance against pathogen infections. This study investigated the potential and related mechanism of oxathiapiprolin to activate the plant disease resistance using the bacterium

Topics: Arabidopsis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Hydrocarbons, Fluorinated; Hydrogen Peroxide; Nicotiana; Oxylipins; Plant Diseases; Plant Immunity; Polymers; Pseudomonas syringae; Pyrazoles; Salicylic Acid; Solanum lycopersicum

Major latex proteins (MLPs) belong to the MLP subfamily in Bet v 1 protein family and respond to both biotic and abiotic stresses, which play critical roles in plant disease resistance. As the type species of widely distributed and economically devastating Potyvirus, Potato virus Y (PVY) is one of the major constraints to important crop plants including tobacco (Nicotiana benthamiana) worldwide. Despite the great losses owing to PVY infection in tobacco, there is no previous study investigating the potential role of MLPs in developing resistance to viral infection.. In this study, for the first time we have identified and functionally analyzed the MLP-like protein 28 from N. benthamiana, denoted as NbMLP28 and investigated its role in conferring resistance to N. benthamiana against PVY infection. NbMLP28 was localized to the plasmalemma and nucleus, with the highest level in the root. NbMLP28 gene was hypothesized to be triggered by PVY infection and was highly expressed in jasmonic acid (JA) signaling pathway. Further validation was achieved through silencing of NbMLP28 through virus-induced gene silencing (VIGS) that rendered N. benthamiana plants more vulnerable to PVY infection, contrary to overexpression that enhanced resistance.. Taken together, this is the first study describing the role of NbMLP28 in tobacco against PVY infection and provide a pivotal point towards obtaining pathogen-resistant tobacco varieties through constructing new candidate genes of MLP subfamily.

Topics: Cell Nucleus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Models, Molecular; Nicotiana; Oxylipins; Plant Diseases; Plant Proteins; Plant Roots; Potyvirus; Protein Conformation; Signal Transduction; Tissue Distribution

The fungal genus Cochliobolus describes necrotrophic pathogens that give rise to significant losses on rice, wheat, and maize. Revealing plant mechanisms of non-host resistance (NHR) against Cochliobolus will help to uncover strategies that can be exploited in engineered cereals. Therefore, we developed a heterogeneous pathosystem and studied the ability of Cochliobolus to infect dicotyledons. We report here that C. miyabeanus and C. heterostrophus infect Arabidopsis accessions and produce functional conidia, thereby demonstrating the ability to accept Brassica spp. as host plants. Some ecotypes exhibited a high susceptibility, whereas others hindered the necrotrophic disease progression of the Cochliobolus strains. Natural variation in NHR among the tested Arabidopsis accessions can advance the identification of genetic loci that prime the plant's defence repertoire. We found that applied phytotoxin-containing conidial fluid extracts of C. miyabeanus caused necrotic lesions on rice leaves but provoked only minor irritations on Arabidopsis. This result implies that C. miyabeanus phytotoxins are insufficiently adapted to promote dicot colonization, which corresponds to a retarded infection progression. Previous studies on rice demonstrated that ethylene (ET) promotes C. miyabeanus infection, whereas salicylic acid (SA) and jasmonic acid (JA) exert a minor function. However, in Arabidopsis, we revealed that the genetic disruption of the ET and JA signalling pathways compromises basal resistance against Cochliobolus, whereas SA biosynthesis mutants showed a reduced susceptibility. Our results refer to the synergistic action of ET/JA and indicate distinct defence systems between Arabidopsis and rice to confine Cochliobolus propagation. Moreover, this heterogeneous pathosystem may help to reveal mechanisms of NHR and associated defensive genes against Cochliobolus infection.

Topics: Arabidopsis; Ascomycota; Cyclopentanes; Disease Resistance; Disease Susceptibility; Ethylenes; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Salicylic Acid; Zea mays

The Mi-1 gene was the first identified and cloned gene that provides resistance to root-knot nematodes (RKNs) in cultivated tomato. However, owing to its temperature sensitivity, this gene does not meet the need for breeding disease-resistant plants that grow under high temperature. In this study, Mi-3 was isolated from the wild species PI 126443 (LA3858) and was shown to display heat-stable resistance to RKNs. However, the mechanism that regulates this resistance remains unknown.. In this study, 4760, 1024 and 137 differentially expressed genes (DEGs) were enriched on the basis of pairwise comparisons (34 °C vs. 25 °C) at 0 (before inoculation), 3 and 6 days post-inoculation (dpi), respectively. A total of 7035 DEGs were identified from line LA3858 in the respective groups under the different soil temperature treatments. At 3 dpi, most DEGs were enriched in Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to plant biotic responses, such as "plant-pathogen interaction" and "plant hormone signal transduction". Significantly enriched DEGs were found to encode key proteins such as R proteins and heat-shock proteins (HSPs). Moreover, other DEGs were found to participate in Ca. Taken together, the results of our study revealed reliable candidate genes from wild materials LA3858, that are related to Mi-3-mediate resistance to Meloidogyne incognita. A large number of vital pathways and DEGs were expressed specifically in accession LA3858 grown at 34 °C and 25 °C soil temperatures at 3 dpi. Upon infection by RKNs, pattern-recognition receptors (PRRs) specifically recognized conserved pathogen-associated molecular patterns (PAMPs) as a result of pathogen-triggered immunity (PTI), and the downstream defensive signal transduction pathway was likely activated through Ca

Topics: Animals; Calcium; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Gene Ontology; Heat-Shock Proteins; Host-Parasite Interactions; Oxylipins; Plant Proteins; Plant Roots; Reactive Oxygen Species; RNA-Seq; Salicylic Acid; Signal Transduction; Solanum; Temperature; Transcription Factors; Transcriptome; Tylenchoidea

Osmotin and osmotin-like proteins (OLPs) play important roles in plant defense responses. The full-length cDNA sequence of an

Topics: Cyclopentanes; Disease Resistance; Fusarium; Humans; Oxylipins; Panax notoginseng; Plant Diseases

OsbHLH034 acts as a positive regulator in jasmonate signaling in rice. Jasmonic acid (JA) is a plant hormone under strict regulation by various transcription factors (TFs) that acts as a signaling compound in the regulation of plant defense responses and development. Here, we report that a basic helix-loop-helix (bHLH)-type TF, OsbHLH034, plays an important role in the JA-mediated resistance response against rice bacterial blight caused by Xanthomonas oryzae pv. oryzae. The expression of OsbHLH034 was upregulated at a late phase after JA treatment. OsbHLH034 interacted with a Jasmonate ZIM-domain (JAZ) protein, OsJAZ9, in both plant and yeast cells. Transgenic rice plants overexpressing OsbHLH034 exhibited a JA-hypersensitive phenotype and increased resistance against rice bacterial blight. Conversely, OsbHLH034-overexpressing plants exhibited high sensitivity to salt stress. The expression of some JA-responsive secretory-type peroxidase genes was upregulated in the OsbHLH034-overexpressing rice plants. Concomitantly, the lignin content significantly increased in these transgenic plants compared to that in the wild-type. These results indicate that OsbHLH034 acts as a positive regulator of the JA-mediated defense response in rice.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Lignin; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Transcription Factors; Xanthomonas

Topics: Antioxidants; Ascorbate Peroxidases; Betaine; Catalase; Catechol Oxidase; Chitinases; Chitosan; Chlorophyll; Cucumis sativus; Cucumovirus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gibberellins; Glucan Endo-1,3-beta-D-Glucosidase; Glutathione Reductase; Host-Pathogen Interactions; Indoleacetic Acids; Lipoxygenase; Oxylipins; Peroxidase; Plant Diseases; Plant Leaves; Plant Proteins; Salicylic Acid; Superoxide Dismutase

Jasmonates (JAs) are important for pathogen resistance in many plants, but the role of these phytohormones in fungal pathogen resistance in rose is unclear. Here, we determined that exogenous application of methyl jasmonate increased resistance to the important fungal pathogen Botrytis cinerea in Rosa chinensis 'Old blush', whereas silencing the JA biosynthetic pathway gene Allene Oxide Synthase (AOS) and JA co-receptor gene CORONATINE INSENSITIVE 1 (COI1) suppressed this response. Transcriptome profiling identified various MYB transcription factor genes that responded to both JA and B. cinerea treatment. Silencing Ri-RcMYB84/Ri-RcMYB123 increased the susceptibility of rose plants to B. cinerea and inhibited the protective effects of JA treatment, confirming the crucial roles of these genes in JA-induced responses to B. cinerea. JAZ1, a key repressor of JA signaling, directly interacts with RcMYB84 and RcMYB123 to deplete their free pools. The JAZ1-RcMYB84 complex binds to the RcMYB123 promoter via the CAACTG motifs to block its transcription. Upon JA treatment, the expression of RcMYB123 is de-repressed, and free forms of RcMYB84 and RcMYB123 are released due to JAZ1 degradation, thereby activating the defense responses of plants to B. cinerea. These findings shed light on the molecular mechanisms underlying JA-induced pathogen resistance in roses.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Rosa; Signal Transduction; Transcription Factors

Topics: Alternaria; Antifungal Agents; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Ontology; Genes, Plant; Oxylipins; Plant Diseases; Plants, Genetically Modified; Respiratory Burst; Salicylic Acid; Signal Transduction; Solanum tuberosum; Ubiquitin

Transcriptomic studies in resistant and susceptible tea cultivars have been performed to reveal the different defense molecular mechanisms of tea after E. onukii feeding. The molecular mechanism by which tea plants respond to small green leafhopper Empoasca onukii (Matsuda) damage is unclear. Using the resistant tea plant cultivar Juyan (JY) and the susceptible tea plant cultivar Enbiao (EB) as materials, this study performed RNA-seq on tea leaf samples collected at three time points (6 h, 12 h, 24 h) during exposure of the plants to leafhopper to reveal the molecular mechanisms that are activated in susceptible and resistant tea plant cultivars in response to leafhopper damage. The numbers of DEGs in the susceptible tea cultivar during early (6 h) and late (24 h) stages of leafhopper induction were higher than those in the resistant cultivar at the same time points. The stress responses to leafhopper were most intense at 12 h in both tea cultivars. Pathway enrichment analysis showed that most up-regulated DEGs and their related metabolic pathways were similar in the two tea cultivars. However, during the early stage of leafhopper induction (6 h), jasmonic acid (JA)-related genes were significantly up-regulated in the resistant cultivar. The terpenoid biosynthetic pathway and the α-linolenic acid metabolic pathway were activated earlier in the resistant cultivar and remained activated until the late stage of leafhopper damage. Our results confirmed that after leafhopper damage, the resistant tea cultivar activated its defense responses earlier than the susceptible cultivar, and these defense responses were mainly related to terpenoid metabolism and JA biosynthetic pathway. The results provide important clues for further studies on resistance strategy of tea plants to pest.

Topics: Animals; Biosynthetic Pathways; Camellia sinensis; Cyclopentanes; Disease Resistance; Hemiptera; Oxylipins; Plant Diseases; Plant Growth Regulators; Terpenes; Transcriptome

Topics: Animals; Antibiosis; Aphids; Chromatography, Liquid; Cyclopentanes; Disease Resistance; DNA-Binding Proteins; Gene Expression Profiling; Gene Ontology; Glucosyltransferases; Glycine max; Host-Parasite Interactions; Mass Spectrometry; Multigene Family; Oxylipins; Plant Defense Against Herbivory; Plant Diseases; Plant Proteins; Protein Domains; Proto-Oncogene Proteins c-myb; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Transcription Factors

CabZIP63 acts positively in the resistance of pepper (Capsicum annuum) to bacterial wilt caused by Ralstonia solanacearum or tolerance to high-temperature/high-humidity stress, but it is unclear how CabZIP63 achieves its functional specificity against R. solanacearum. Here, CaASR1, an abscisic acid-, stress-, and ripening-inducible protein of C. annuum, was functionally characterized in modulating the functional specificity of CabZIP63 during the defense response of pepper to R. solanacearum. In pepper plants inoculated with R. solanacearum, CaASR1 was up-regulated before 24 h post-inoculation but down-regulated thereafter, and was down-regulated by high-temperature/high-humidity stress. Data from gene silencing and transient overexpression experiments indicated that CaASR1 acts as a positive regulator in the immunity of pepper against R. solanacearum and a negative regulator of thermotolerance. Pull-down combined with mass spectrometry revealed that CaASR1 interacted with CabZIP63 upon R. solanacearum infection; the interaction was confirmed by microscale thermophoresis and bimolecular fluorescence complementation assays.CaASR1 silencing upon R. solanacearum inoculation repressed CabZIP63-mediated transcription from the promoters of the salicylic acid (SA)-dependent CaPR1 and CaNPR1, but derepressed transcription of CaHSP24 and the jasmonic acid (JA)-dependent CaDEF1. Our findings suggest that CaASR1 acts as a positive regulator of the defense response of pepper to R. solanacearum by interacting with CabZIP63, enabling it to promote SA-dependent but repress JA-dependent immunity and thermotolerance during the early stages of infection.

Topics: Capsicum; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Immunity; Plant Proteins; Ralstonia solanacearum; Salicylic Acid; Transcription Factors

Jasmonates (JAs) are important regulators of plant growth, development, and defense. ATP-binding cassette (ABC) transporters participate in disease resistance by transporting JAs or antimicrobial secondary metabolites in dicotyledons. Here, we functionally characterized a JAs-inducible rice gene (OsPDR1) that encodes a member of the pleiotropic drug resistance (PDR) subfamily of ABC transporters. By affecting JAs biosynthesis, overexpression of OsPDR1 resulted in constitutive activation of defense-related genes and enhanced resistance to bacterial blight, whereas its mutation decreased pathogen resistance. In addition, overexpression and mutation of OsPDR1 resulted in decreased and increased plant growth at seedling stage, respectively, but eventually led to decreased grain yield. OsPDR1 encodes three splice isoforms, of which OsPDR1.2 and OsPDR1.3 contain a conserved glutamate residue in the "ENI-motif" of the first nucleotide-binding domain, while OsPDR1.1 does not. The three OsPDR1 transcripts are developmentally controlled and differentially regulated by JAs and pathogen infection. The OsPDR1.2- and OsPDR1.3-overexpressing plants exhibited higher JAs content and stronger growth inhibition and disease resistance than OsPDR1.1-overexpressing plants. These results indicated that alternative splicing affects the function of OsPDR1 gene in regulation of growth, development and disease resistance.

Topics: Amino Acid Sequence; ATP-Binding Cassette Transporters; Cyclopentanes; Disease Resistance; Magnaporthe; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Sequence Alignment

Tomato gray leaf spot caused by Stemphylium lycopersici (S. lycopersici) is a serious disease that can severely hinder tomato production. To date, only Sm has been reported to provide resistance against this disease, and the molecular mechanism underlying resistance to this disease in tomato remains unclear. To better understand the mechanism of tomato resistance to S. lycopersici, real-time quantitative reverse transcription-polymerase chain reaction (qRT-PCR)-based analysis, physiological indexes, microscopy observations and transgenic technology were used in this study.. Our results showed that the expression of SlERF01 was strongly induced by S. lycopersici and by exogenous applications of the hormones salicylic acid (SA) and jasmonic acid (JA). Furthermore, overexpression of SlERF01 enhanced the hypersensitive response (HR) to S. lycopersici and elevated the expression of defense genes in tomato. Furthermore, the accumulation of lignin, callose and hydrogen peroxide (H. We identified the SlERF01 gene, which encodes a novel tomato AP2/ERF transcription factor (TF). Functional analysis revealed that SlERF01 positively regulates tomato resistance to S. lycopersici. Our findings indicate that SlERF01 plays a key role in multiple SA, JA and ROS signaling pathways to provide resistance to invasion by S. lycopersici. The findings of this study not only help to better understand the mechanisms of response to pathogens but also enable targeted breeding strategies for tomato resistance to S. lycopersici.

Topics: Ascomycota; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Genes, Plant; Oxylipins; Phylogeny; Plant Diseases; Plant Proteins; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Transcription Factors

Molecular mechanisms associated with biochar-elicited suppression of soilborne plant diseases and improved plant performance are not well understood. A stem base inoculation approach was used to explore the ability of biochar to induce systemic resistance in tomato plants against crown rot caused by a soilborne pathogen, Fusarium oxysporum f. sp. radicis lycopersici. RNA-seq transcriptome profiling of tomato, and experiments with jasmonic and salycilic acid deficient tomato mutants, were performed to elucidate the in planta molecular mechanisms involved in induced resistance. Biochar (produced from greenhouse plant wastes) was found to mediate systemic resistance against Fusarium crown rot and to simultaneously improve tomato plant growth and physiological parameters by up to 63%. Transcriptomic analysis (RNA-seq) of tomato demonstrated that biochar had a priming effect on gene expression and upregulated the pathways and genes associated with plant defense and growth such as jasmonic acid, brassinosteroids, cytokinins, auxin and synthesis of flavonoid, phenylpropanoids and cell wall. In contrast, biosynthesis and signaling of the salicylic acid pathway was downregulated. Upregulation of genes and pathways involved in plant defense and plant growth may partially explain the significant disease suppression and improvement in plant performance observed in the presence of biochar.

Topics: Charcoal; Cyclopentanes; Disease Resistance; Fusarium; Gene Expression Profiling; Oxylipins; Plant Diseases; Plant Roots; Salicylic Acid; Solanum lycopersicum; Transcriptome

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Fusarium; Inositol; Oxylipins; Plant Diseases; Salicylic Acid; Signal Transduction

Tomato is one of the most popular horticultural crops, and many commercial tomato cultivars are particularly susceptible to Botrytis cinerea. Non-expressor of pathogenesis-related gene 1 (NPR1) is a critical component of the plant defense mechanisms. However, our understanding of how SlNPR1 influences disease resistance in tomato is still limited. In this study, two independent slnpr1 mutants were used to study the role of SlNPR1 in tomato resistance against B. cinerea. Compared to (WT), slnpr1 leaves exhibited enhanced resistance against B. cinerea with smaller lesion sizes, higher activities of chitinase (CHI), β-1, 3-glucanases (GLU) and phenylalanine ammonia-lyase (PAL), and significantly increased expressions of pathogenesis-related genes (PRs). The increased activities of peroxidase (POD), ascorbate peroxidase (APX) and decreased catalase (CAT) activities collectively regulated reactive oxygen species (ROS) homeostasis in slnpr1 mutants. The integrity of the cell wall in slnpr1 mutants was maintained. Moreover, the enhanced resistance was further reflected by induction of defense genes involved in jasmonic acid (JA) and ethylene (ET) signaling pathways. Taken together, these findings revealed that knocking out SlNPR1 resulted in increased activities of defense enzymes, changes in ROS homeostasis and integrity of cell walls, and activation of JA and ET pathways, which confers resistance against B. cinerea in tomato plants.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Knockout Techniques; Homeostasis; Humans; Oxylipins; Plant Diseases; Plant Proteins; Reactive Oxygen Species; Solanum lycopersicum

Rice blast, caused by the fungus Magnaporthe oryzae, is a highly damaging disease. Introducing genes, which confer a broad spectrum resistance to the disease, such as Pib, makes an important contribution to protecting rice production. However, little is known regarding the mechanistic basis of the products of such genes. In this study, transcriptome of the cultivar Lijiangxintuanheigu (LTH) and its monogenic IRBLb-B which harbors Pib treated with M. oryzae were compared. Among the many genes responding transcriptionally to infection were some encoding products involved in the metabolism of ROS (reactive oxygen species), in jasmonate (JA) metabolism, and WRKY transcription factors, receptor kinases, and resistance response signal modulation. The down-regulation of genes encoding peroxiredoxin and glutathione S transferases implied that the redox homeostasis is essential for the expression of Pib-mediated resistance. The up-regulation of seven disease resistance-related genes, including three encoding a NBS-LRR protein, indicated that disease resistance-related genes are likely tend to support the expression of Pib resistance. These data revealed that potential candidate genes and transcriptional reprogramming were involved in Pib-mediated resistance mechanisms.

Topics: Ascomycota; Computational Biology; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Transcription Factors; Transcriptome

Oligogalacturonides (OGAs) are a biologically active carbohydrate derived from homogalacturonan, a major element of cell wall pectin. OGAs induced resistance and mechanism were assessed in Arabidopsis thaliana-Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) interaction. The effective resistance was mainly observed at 25 mg/L OGAs with reduced disease index, bacterial multiplication, higher transcript level of salicylic acid (SA) pathway related genes (PR1, PR2, PR5) and jasmonic acid (JA) pathway related genes (PDF1.2, VSP2) as well as SA, JA content and production of reactive oxygen species (ROS), nitric oxide (NO). In SA (NahG, sid2) and JA (jar1) deficient mutants, disease severity indicated that both SA and JA pathways are necessary for Arabidopsis response to Pst DC3000. OGAs triggered less resistance to Pst DC3000 in JA-deficient mutant, and SA-deficient mutants signifying that SA and JA play redundant roles in OGAs induced resistance. Therefore, these evidences further reveal the signaling pathways of OGAs resistance, which is conducive to its application in agriculture to protect plants from diseases.

Topics: Arabidopsis; Chemical Phenomena; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Metabolic Networks and Pathways; Monosaccharides; Nitric Oxide; Oligosaccharides; Oxylipins; Phenotype; Plant Diseases; Plant Leaves; Pseudomonas syringae; Reactive Oxygen Species; Salicylic Acid; Spectrum Analysis

Green leaf volatiles (GLVs) can induce defence priming, that is, can enable plants to respond faster or more strongly to future stress. The effects of priming by GLVs on defence against insect herbivores and pathogens have been investigated, but little is known about the potential of GLVs to prime crops against virus transmission by vector insects. Here, we tested the hypothesis that exposure to the GLV Z-3-hexenol (Z-3-HOL) can prime tomato (Solanum lycopersicum) for an enhanced defence against subsequent Tomato yellow leaf curl virus (TYLCV) transmission by the whitefly Bemisia tabaci. Bioassays showed that Z-3-HOL priming reduced subsequent plant susceptibility to TYLCV transmission by whiteflies. Z-3-HOL treatment increased transcripts of jasmonic acid (JA) biosynthetic genes and increased whitefly-induced transcripts of salicylic acid (SA) biosynthetic genes in plants. Using chemical inducers, transgenics and mutants, we demonstrated that induction of JA reduced whitefly settling and successful whitefly inoculation, while induction of SA reduced TYLCV transmission by whiteflies. Defence gene transcripts and flavonoid levels were enhanced when whiteflies fed on Z-3-HOL-treated plants. Moreover, Z-3-HOL treatment reduced the negative impact of whitefly infestation on tomato growth. These findings suggest that Z-3-HOL priming may be a valuable tool for improving management of insect-transmitted plant viruses.

Topics: Animals; Begomovirus; Cyclopentanes; Disease Resistance; Hemiptera; Hexanols; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Salicylic Acid; Solanum lycopersicum; Volatile Organic Compounds

Nitrogen (N), phosphorus (P), and potassium (K) are three essential macro-elements for plant growth and development. Used to improve yield in agricultural production, the excessive use of chemical fertilizers often leads to increased production costs and ecological environmental pollution. Vitamins C and E are antioxidants that play an important role in alleviating abiotic stress. However, there are few studies on alleviating oxidative stress caused by macro-element deficiency. Here, we used Arabidopsis vitamin E synthesis-deficient mutant

Topics: Antioxidants; Arabidopsis; Arabidopsis Proteins; Ascorbic Acid; Chlorophyll; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Malondialdehyde; Oxidative Stress; Oxylipins; Plant Diseases; Plant Leaves; Reactive Oxygen Species; Seedlings; Seeds; Signal Transduction; Time Factors; Vitamin E

Fusarium oxysporum f. sp. niveum (FON) causes Fusarium wilt in watermelon. Several disease-resistant watermelon varieties have been developed to combat Fusarium wilt. However, the key metabolites that mount defense responses in these watermelon varieties are unknown. Herein, we analyzed hormones, melatonin, phenolic acids, and amino acid profiles in the leaf tissue of FON zero (0)-resistant (PI-296341, Calhoun Grey, and Charleston Grey) and -susceptible (Sugar Baby) watermelon varieties before and after infection.. We found that jasmonic acid-isoleucine (JA-Ile) and methyl jasmonate (MeJA) were selectively accumulated in one or more studied resistant varieties upon infection. However, indole-3-acetic acid (IAA) was only observed in the FON 0 inoculated plants of all varieties on the 16th day of post-inoculation. The melatonin content of PI-296341 decreased upon infection. Conversely, melatonin was only detected in the FON 0 inoculated plants of Sugar Baby and Charleston Grey varieties. On the 16th day of post-inoculation, the lysine content in resistant varieties was significantly reduced, whereas it was found to be elevated in the susceptible variety.. Taken together, Me-JA, JA-Ile, melatonin, and lysine may have crucial roles in developing defense responses against the FON 0 pathogen, and IAA can be a biomarker of FON 0 infection in watermelon plants.

Topics: Acetates; Amino Acids; Citrullus; Cyclopentanes; Disease Resistance; Fusarium; Host-Pathogen Interactions; Hydroxybenzoates; Lysine; Melatonin; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves

Red rot caused by Colletotrichum falcatum poses a serious threat to sugarcane cultivation in many tropical and sub-tropical countries. Deciphering the molecular network of major defense-signaling pathways in sugarcane cultivars with varying red rot resistance is essential to elucidate the phenomenon of defense priming exerted by resistance inducers. Therefore, in this study, expression pattern of transcripts coding for major defense-signaling pathway regulatory genes was profiled during compatible and incompatible interactions and in response to defense priming using qRT-PCR. Candidate genes that were profiled are involved in or related to hypersensitive response and reactive oxygen species production (HR/ROS), salicylic acid (SA), and jasmonic acid/ethylene (JA/ET) pathways. For compatible and incompatible interactions, susceptible (CoC 671), field tolerant (Co 86032) and resistant (Co 93009) sugarcane cultivars were used, whereas for defense priming, benzothiadiazole (BTH) and the pathogen-associated molecular patterns (PAMPs) of C. falcatum viz., CfEPL1 (eliciting plant response-like) and CfPDIP1 (plant defense inducing protein) were used in CoC 671 cultivar. Results indicated that the master regulator of defense pathways, nonexpressor of pathogenesis-related genes 1 (NPR1) was highly upregulated in incompatible interactions (in both Co 86032 and Co 93009) than the compatible interaction along with SA pathway-associated genes. Similarly, in response to defense priming with BTH, CfEPL1 and CfPDIP1, only the SA pathway-associated genes showed considerable upregulation at 0 h post inoculation (hpi) and other intermittent time points. Overall, this study showed that SA-mediated defense pathway is the most predominant pathway reprogrammed during priming with BTH, CfEPL1 and CfPDIP1 and substantiated the earlier findings that these agents indeed induce systemic resistance against red rot of sugarcane.

Topics: Colletotrichum; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Proteins; Reactive Oxygen Species; Saccharum; Salicylic Acid; Signal Transduction

Clubroot, caused by

Topics: Brassica napus; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Genes, Plant; Models, Biological; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Tumors; Plasmodiophorida; RNA, Plant; Salicylic Acid; Stress, Physiological

Squamosa promoter binding protein (SBP)-box genes are plant-specific transcription factors involved in plant growth and development, morphogenesis and biotic and abiotic stress responses. However, these genes have been understudied in pepper, especially with respect to defense responses to

Topics: Arabidopsis; Capsicum; Cell Nucleus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Models, Biological; Mutation; Nicotiana; Oxylipins; Phenotype; Phytophthora; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Protein Transport; Signal Transduction

Prolonged mechanical stress (MS) causes thigmomorphogenesis, a stress acclimation response associated with increased disease resistance. What remains unclear is if; 1) plants pre-exposed to a short period of repetitive MS can prime defence responses upon subsequent challenge with necrotrophic pathogens, 2) MS mediates plant immunity via jasmonic acid (JA) signalling, and 3) a short period of repetitive MS can cause long-term changes in gene expression resembling a stress-induced memory. To address these points, 10-days old juvenile Arabidopsis seedlings were mechanically stressed for 7-days using a soft brush and subsequently challenged with the necrotrophic pathogens, Alternaria brassicicola, and Botrytis cinerea. Here we assessed how MS impacted structural cell wall appositions, disease symptoms and altered gene expression in response to infection.. The MS-treated plants exhibited enhanced cell wall appositions and jasmonic acid (JA) accumulation that correlated with a reduction in disease progression compared to unstressed plants. The expression of genes involved in JA signalling, callose deposition, peroxidase and phytoalexin biosynthesis and reactive oxygen species detoxification were hyper-induced 4-days post-infection in MS-treated plants. The loss-of-function in JA signalling mediated by the JA-insensitive coronatine-insensitive 1 (coi1) mutant impaired the hyper-induction of defense gene expression and promoted pathogen proliferation in MS-treated plants subject to infection. The basal expression level of PATHOGENESIS-RELATED GENE 1 and PLANT DEFENSIN 1.2 defense marker genes were constitutively upregulated in rosette leaves for 5-days post-MS, as well as in naïve cauline leaves that differentiated from the inflorescence meristem well after ceasing MS.. This study reveals that exposure of juvenile Arabidopsis plants to a short repetitive period of MS can alter gene expression and prime plant resistance upon subsequent challenge with necrotrophic pathogens via the JA-mediated COI1 signalling pathway. MS may facilitate a stress-induced memory to modulate the plant's response to future stress encounters. These data advance our understanding of how MS primes plant immunity against necrotrophic pathogens and how that could be utilised in sustainable agricultural practices.

Topics: Alternaria; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Models, Genetic; Mutation; Oxylipins; Plant Diseases; Plant Immunity; Plant Leaves; Salicylic Acid; Seedlings; Stress, Mechanical

WRKY genes and jasmonic acid (JA) play a crucial role in plants' responses against biotic and abiotic stress. However, the regulating mechanism of WRKY genes on strawberry fruits' resistance against

Topics: Amino Acid Sequence; Botrytis; Cyclopentanes; Disease Resistance; Fragaria; Gene Expression Profiling; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Oxylipins; Phylogeny; Plant Diseases; Plant Growth Regulators; Plant Immunity; Plant Proteins; RNA, Small Interfering; Sequence Alignment; Sequence Homology, Amino Acid; Transcription Factors

Plant defense responses to biotic stresses are complex biological processes, all governed by sophisticated molecular regulations. Induced systemic resistance (ISR) is one of these defense mechanisms where beneficial bacteria or fungi prime plants to resist pathogens or pest attacks. In ISR, the defense arsenal in plants remains dormant and it is only triggered by an infection, allowing a better allocation of plant resources. Our group recently described that the well-known beneficial bacterium Paraburkholderia phytofirmans PsJN is able to induce Arabidopsis thaliana resistance to Pseudomonas syringae pv. tomato (Pst) DC3000 through ISR, and that ethylene, jasmonate and salicylic acid are involved in this protection. Nevertheless, the molecular networks governing this beneficial interaction remain unknown. To tackle this issue, we analyzed the temporal changes in the transcriptome of PsJN-inoculated plants before and after being infected with Pst DC3000. These data were used to perform a gene network analysis to identify highly connected transcription factors. Before the pathogen challenge, the strain PsJN regulated 405 genes (corresponding to 1.8% of the analyzed genome). PsJN-inoculated plants presented a faster and stronger transcriptional response at 1-hour post infection (hpi) compared with the non-inoculated plants, which presented the highest transcriptional changes at 24 hpi. A principal component analysis showed that PsJN-induced plant responses to the pathogen could be differentiated from those induced by the pathogen itself. Forty-eight transcription factors were regulated by PsJN at 1 hpi, and a system biology analysis revealed a network with four clusters. Within these clusters LHY, WRKY28, MYB31 and RRTF1 are highly connected transcription factors, which could act as hub regulators in this interaction. Concordantly with our previous results, these clusters are related to jasmonate, ethylene, salicylic, acid and ROS pathways. These results indicate that a rapid and specific response of PsJN-inoculated plants to the virulent DC3000 strain could be the pivotal element in the protection mechanism.

Topics: Arabidopsis; Burkholderiaceae; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Regulatory Networks; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Principal Component Analysis; Pseudomonas syringae; Salicylic Acid; Transcription Factors; Transcriptome

Metabolic pathways are interconnected and yet relatively independent. Genes involved in metabolic modules are required for the modules to run. Study of the relationships between genes and metabolic modules improves the understanding of metabolic pathways in plants. The WIN transcription factor activates the cuticle biosynthesis pathway and promotes cuticle biosynthesis. The relationship between the WIN transcription factor and other metabolic pathways is unknown. Our aim was to determine the relationships between the main genes involved in cuticle biosynthesis and those involved in other metabolic pathways. We did this by cloning a cotton WIN gene, GhWIN2, and studying its influence on other pathways.. As with other WIN genes, GhWIN2 regulated expression of cuticle biosynthesis-related genes, and promoted cuticle formation. Silencing of GhWIN2 resulted in enhanced resistance to Verticillium dahliae, caused by increased content of salicylic acid (SA). Moreover, silencing of GhWIN2 suppressed expression of jasmonic acid (JA) biosynthesis-related genes and content. GhWIN2 positively regulated the fatty acid biosynthesis pathway upstream of the JA biosynthesis pathway. Silencing of GhWIN2 reduced the content of stearic acid, a JA biosynthesis precursor.. GhWIN2 not only regulated the cuticle biosynthesis pathway, but also positively influenced JA biosynthesis and negatively influenced SA biosynthesis.

Topics: Amino Acid Sequence; Cyclopentanes; Disease Resistance; Gossypium; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Salicylic Acid; Sequence Alignment; Verticillium

DOF proteins are plant-specific transcription factors that play vital roles in plant development and defense responses. However, DOFs have primarily been investigated in model plants, and fairly limited research has been performed on grape (Vitis vinifera). In this study, we isolated and characterized a C

Topics: Cyclopentanes; Disease Resistance; Oxylipins; Plant Diseases; Plant Proteins; Salicylic Acid; Transcription Factors; Vitis

Calmodulin (CaM) regulates plant disease responses through its downstream calmodulin-binding proteins (CaMBPs) often by affecting the biosynthesis or signaling of phytohormones, such as jasmonic acid (JA) and salicylic acid. However, how these CaMBPs mediate plant hormones and other stress resistance-related signaling remains largely unknown. In this study, we conducted analyses in Arabidopsis (

Topics: Amino Acid Motifs; Arabidopsis; Arabidopsis Proteins; Botrytis; Calcium Signaling; Calmodulin-Binding Proteins; Cyclopentanes; Disease Resistance; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Stomata; Salicylic Acid

The reduction of synthetic fungicides in agriculture is necessary to guarantee a sustainable production that protects the environment and consumers' health. Downy mildew caused by the oomycete Plasmopara viticola is the major pathogen in viticulture worldwide and responsible for up to 60% of pesticide treatments. Alternatives to reduce fungicides are thus utterly needed to ensure sustainable vineyard-ecosystems, consumer health and public acceptance. Essential oils (EOs) are amongst the most promising natural plant protection alternatives and have shown their antibacterial, antiviral and antifungal properties on several agricultural crops. However, the efficiency of EOs highly depends on timing, application method and the molecular interactions between the host, the pathogen and EO. Despite proven EO efficiency, the underlying processes are still not understood and remain a black box. The objectives of the present study were: a) to evaluate whether a continuous fumigation of a particular EO can control downy mildew in order to circumvent the drawbacks of direct application, b) to decipher molecular mechanisms that could be triggered in the host and the pathogen by EO application and c) to try to differentiate whether essential oils directly repress the oomycete or act as plant resistance primers. To achieve this a custom-made climatic chamber was constructed that enabled a continuous fumigation of potted vines with different EOs during long-term experiments. The grapevine (Vitis vinifera) cv Chasselas was chosen in reason of its high susceptibility to Plasmopara viticola. Grapevine cuttings were infected with P. viticola and subsequently exposed to continuous fumigation of different EOs at different concentrations, during 2 application time spans (24 hours and 10 days). Experiments were stopped when infection symptoms were clearly observed on the leaves of the control plants. Plant physiology (photosynthesis and growth rate parameters) were recorded and leaves were sampled at different time points for subsequent RNA extraction and transcriptomics analysis. Strikingly, the Oregano vulgare EO vapour treatment during 24h post-infection proved to be sufficient to reduce downy mildew development by 95%. Total RNA was extracted from leaves of 24h and 10d treatments and used for whole transcriptome shotgun sequencing (RNA-seq). Sequenced reads were then mapped onto the V. vinifera and P. viticola genomes. Less than 1% of reads could be mapped onto the P. viticol

Topics: Cyclopentanes; Disease Resistance; Fumigation; Fungicides, Industrial; Gene Expression Profiling; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Immunity, Innate; Oils, Volatile; Oomycetes; Origanum; Oxylipins; Photosynthesis; Phytoalexins; Plant Diseases; Plant Leaves; Plant Oils; Sesquiterpenes; Vitis

This study was carried out to fabricate nickel oxide nanostructures (NONS) and to evaluate its ability to control Cucumber mosaic virus (CMV) by direct antiviral activity as well as induction of systemic resistance in treated cucumber plants. The efficacy of nickel oxide nanostructures for control CMV in cucumber plants was biologically evaluated by a reduction in disease severity, reduction in CMV accumulation and expression of regulatory and defense-related genes. Cucumber plants treated with nickel oxide nanostructures showed incredible suppression of CMV infection compared with non-treated plants. The enzyme-linked immunosorbent assay (ELISA) showed a marked reduction in CMV accumulation in cucumber plants treated with nickel oxide nanostructures compared to untreated plants. Based on real-time polymerase chain reaction (RT-PCR) test, cucumber plants treated with nickel oxide nanostructures showed increased expression of regulatory and defense-related genes concerned in salicylic acid (SA) and jasmonic acid (JA)/ethylene (ET) signaling pathways. NONS nanostructures showed direct antiviral activity against CMV resulted in significant reduction in CMV severity and titer relative to untreated plants. Treatment with nickel oxide nanostructures significantly improved cucumber fresh and dry weights as well as number of leaves. The induction of systemic resistance towards CMV by NONS nanostructures considered a novel strategy and first report.

Topics: Antiviral Agents; Cucumis sativus; Cucumovirus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Nanostructures; Nickel; Oxylipins; Plant Diseases; Plant Leaves; Salicylic Acid; Signal Transduction

Multiprotein bridging factor 1 s (MBF1s) are members of the transcriptional co-activator family that have involved in plant growth, development and stress responses. However, little is known about the Solanum lycopersicum MBF1 (SlMBF1) gene family.. In total, five SlMBF1 genes were identified based on the tomato reference genome, and these genes were mapped to five chromosomes. All of the SlMBF1 proteins were highly conserved, with a typical MBF1 domain and helix-turn-helix_3 domain. In addition, the promoter regions of the SlMBF1 genes have various stress and hormone responsive cis-regulatory elements. Encouragingly, the SlMBF1 genes were expressed with different expression profiles in different tissues and responded to various stress and hormone treatments. The biological function of SlMBF1c was further identified through its overexpression in tomato, and the transgenic tomato lines showed increased susceptibility to Botrytis cinerea (B. cinerea). Additionally, the expression patterns of salicylic acid (SA)-, jasmonic acid (JA)- and ethylene (ET)- mediated defense related genes were altered in the transgenic plants.. Our comprehensive analysis provides valuable information for clarifying the evolutionary relationship of the SlMBF1 members and their expression patterns in different tissues and under different stresses. The overexpression of SlMBF1c decreased the resistance of tomato to B. cinerea through enhancing the gene expression of the SA-mediated signaling pathway and depressing JA/ET-mediated signaling pathways. These results will facilitate future functional studies of the transcriptional co-activator family.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Multigene Family; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Stress, Physiological; Transcription Factors

White rot is one of the most dangerous fungal diseases and can considerably affect grape berry production and quality. However, few studies have focused on this disease, and thus, finding candidate white rot resistance genes is of great importance for breeding resistant grapevine cultivars. Based on field observations and indoor experiments, the cultivars "Victoria" and "Zhuosexiang" showed significant differences in white rot resistance. For understanding the molecular mechanisms behind it, different phenotypes of grapevine leaves were used for RNA sequencing via Illumina and single-molecule real-time (SMRT) sequencing technology.. A transcript library containing 53,906 reads, including known and novel transcripts, was constructed following the full-length transcriptome sequencing of the two grapevine cultivars. Genes involved in salicylic acid (SA) and jasmonic acid (JA) synthesis pathways showed different expression levels. Furthermore, four key transcription factors (TFs), NPR1, TGA4, Pti6, and MYC2, all involved in the SA and JA signal pathways were identified, and the expression profile revealed the different regulation of the pathogenesis related protein1 (PR1) resistance gene, as mediated by the four TFs.. Full-length transcript sequencing can substantially improve the accuracy and integrity of gene prediction and gene function research in grapevine. Our results contribute to identify candidate resistance genes and improve our understanding of the genes and regulatory mechanisms involved in grapevine resistance to white rot.

Topics: Cyclopentanes; Disease Resistance; Fruit; High-Throughput Nucleotide Sequencing; Oxylipins; Plant Breeding; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Salicylic Acid; Sequence Analysis, RNA; Transcription Factors; Vitis

Potato plants treated with the pathogen-associated molecular pattern Pep-13 mount salicylic acid- and jasmonic acid-dependent defense responses, leading to enhanced resistance against Phytophthora infestans, the causal agent of late blight disease. Recognition of Pep-13 is assumed to occur by binding to a yet unknown plasma membrane-localized receptor kinase. The potato genes annotated to encode the co-receptor BAK1, StSERK3A and StSERK3B, are activated in response to Pep-13 treatment. Transgenic RNAi-potato plants with reduced expression of both SERK3A and SERK3B were generated. In response to Pep-13 treatment, the formation of reactive oxygen species and MAP kinase activation, observed in wild type plants, is highly reduced in StSERK3A/B-RNAi plants, suggesting that StSERK3A/B are required for perception of Pep-13 in potato. In contrast, defense gene expression is induced by Pep-13 in both control and StSERK3A/B-depleted plants. Altered morphology of StSERK3A/B-RNAi plants correlates with major shifts in metabolism, as determined by untargeted metabolite profiling. Enhanced levels of hydroxycinnamic acid amides, typical phytoalexins of potato, in StSERK3A/B-RNAi plants are accompanied by significantly decreased levels of flavonoids and steroidal glycoalkaloids. Thus, altered metabolism in StSERK3A/B-RNAi plants correlates with the ability of StSERK3A/B-depleted plants to mount defense, despite highly decreased early immune responses.

Topics: Alkaloids; Amides; Coumaric Acids; Cyclopentanes; Disease Resistance; Flavonoids; Gene Expression Regulation, Plant; Isoenzymes; Metabolome; Oxylipins; Pathogen-Associated Molecular Pattern Molecules; Phytoalexins; Phytophthora infestans; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Protein Serine-Threonine Kinases; Reactive Oxygen Species; Receptors, Pattern Recognition; RNA, Small Interfering; Salicylic Acid; Sesquiterpenes; Solanum tuberosum

Apocarotenoids, such as β-cyclocitral, α-ionone, β-ionone, and loliolide, are derived from carotenes via chemical or enzymatic processes. Recent studies revealed that β-cyclocitral and loliolide play an important role in various aspects of plant physiology, such as stress responses, plant growth, and herbivore resistance. However, information on the physiological role of α-ionone is limited. We herein investigated the effects of α-ionone on plant protection against herbivore attacks. The pretreatment of whole tomato (

Topics: Animals; Arabidopsis; Cyclopentanes; Disease Resistance; Female; Flowers; Gene Expression Regulation, Plant; Norisoprenoids; Oxylipins; Plant Diseases; Plant Proteins; Solanum lycopersicum; Thysanoptera

Brown plant hopper (BPH) is one of the major destructive insect pests of rice, causing severe yield loss. Thirty-two BPH resistance genes have been identified in cultivated and wild species of rice Although, molecular mechanism of rice plant resistance against BPH studied through map-based cloning, due to non-existence of NMR/crystal structures of Bph14 protein, recognition of leucine-rich repeat (LRR) domain and its interaction with different ligands are poorly understood. Thus, in the present study, in silico approach was adopted to predict three-dimensional structure of LRR domain of Bph14 using comparative modelling approach followed by interaction study with jasmonic and salicylic acids. LRR domain along with LRR-jasmonic and salicylic acid complexes were subjected to dynamic simulation using GROMACS, individually, for energy minimisation and refinement of the structure. Final binding energy of jasmonic and salicylic acid with LRR domain was calculated using MM/PBSA. Free-energy landscape analysis revealed that overall stability of LRR domain of Bph14 is not much affected after forming complex with jasmonic and salicylic acid. MM/PBSA analysis revealed that binding affinities of LRR domain towards salicylic acid is higher as compared to jasmonic acid. Interaction study of LRR domain with salicylic acid and jasmonic acid reveals that THR987 of LRR form hydrogen bond with both complexes. Thus, THR987 plays active role in the Bph14 and phytochemical interaction for inducing resistance in rice plant against BPH. In future, Bph14 gene and phytochemicals could be used in BPH management and development of novel resistant varieties for increasing rice yield.

Topics: Algorithms; Amino Acid Sequence; Animals; Binding Sites; Chemical Phenomena; Cyclopentanes; Disease Resistance; Hydrogen Bonding; Insecta; Ligands; Models, Molecular; Molecular Docking Simulation; Molecular Dynamics Simulation; Oryza; Oxylipins; Plant Proteins; Protein Binding; Protein Conformation; Protein Interaction Domains and Motifs; Salicylic Acid; Structure-Activity Relationship

Plants have evolved a sophisticated two-branch defence system to prevent the growth and spread of pathogen infection. The novel Cys-rich repeat (CRR) containing receptor-like kinases, known as CRKs, were reported to mediate defence resistance in plants. For rice, there are only two reports of CRKs. A semi-dominant lesion mimic mutant als1 (apoptosis leaf and sheath 1) in rice was identified to demonstrate spontaneous lesions on the leaf blade and sheath. A map-based cloning strategy was used for fine mapping and cloning of ALS1, which was confirmed to be a typical CRK in rice. Functional studies of ALS1 were conducted, including phylogenetic analysis, expression analysis, subcellular location and blast resistance identification. Most pathogenesis-related (PR) genes and other defence-related genes were activated and up-regulated to a high degree. ALS1 was expressed mainly in the leaf blade and sheath, in which further study revealed that ALS1 was present in the vascular bundles. ALS1 was located in the cell membrane of rice protoplasts, and its mutation did not change its subcellular location. Jasmonic acid (JA) and salicylic acid (SA) accumulation were observed in als1, and enhanced blast resistance was also observed. The mutation of ALS1 caused a constitutively activated defence response in als1. The results of our study imply that ALS1 participates in a defence response resembling the common SA-, JA- and NH1-mediated defence responses in rice.

Topics: Amino Acid Sequence; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Dominant; Genes, Plant; Mutation; Oryza; Oxylipins; Phenotype; Plant Diseases; Plant Leaves; Plant Proteins; Protein Serine-Threonine Kinases; Salicylic Acid

Rhg1 (resistance to Heterodera glycines 1) is an important locus that contributes to resistance against soybean cyst nematode (SCN; Heterodera glycines Ichinohe), which is the most economically damaging disease of soybean worldwide. Simultaneous overexpression of three genes encoding a predicted amino acid transporter, an α-soluble N-ethylmaleimide-sensitive factor attachment protein (α-SNAP) and a predicted wound-induced protein resulted in resistance to SCN provided by this locus. However, the roles of two of these genes (excluding α-SNAP) remain unknown. Here, we report the functional characterization of Glyma.18G022400, a gene at the Rhg1 locus that encodes the predicted amino acid transporter Rhg1-GmAAT. Although the direct role of Rhg1-GmAAT in glutamate transport was not demonstrated, multiple lines of evidence showed that Rhg1-GmAAT impacts glutamic acid tolerance and glutamate transportation in soybean. Transcriptomic and metabolite profiling indicated that overexpression of Rhg1-GmAAT activated the jasmonic acid (JA) pathway. Treatment with a JA biosynthesis inhibitor reduced the resistance provided by the Rhg1-containing PI88788 to SCN, which suggested that the JA pathway might play a role in Rhg1-mediated resistance to SCN. Our results could be helpful for the clarification of the mechanism of resistance to SCN provided by Rhg1 in soybean.

Topics: Amino Acid Transport Systems; Animals; Cyclopentanes; Disease Resistance; Glutamates; Glycine max; Oxylipins; Plant Diseases; Tylenchoidea

Plant GH3 genes are key components of the hormonal mechanism regulating growth and development, responding to biotic and abiotic stress. GH3 proteins are involved in hormonal homeostasis through conjugation to amino acids of the free form of salicylic acid, jasmonic acid (JA) or indole-3-acetic acid (IAA). Our previous work has uncovered that two GH3 genes encoding IAA-amido synthetase play important roles in the resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) in rice, however, whether other rice GH3 genes play roles in resistance to Xoo is unclear. Here, we validated that GH3.3, GH3.5, GH3.6 and GH3.12, four members of group I GH3 family, are the functional JA-Ile synthetases by catalyzing the conversion of free JA into active form of JA-Ile in vitro and in vivo. The overexpressing plants of four genes individually accumulated less JA but more JA-Ile than the wild type plants. Conversely, the corresponding suppressing plants of four genes contained comparable JA and JA-Ile concentrations, but the triple and quadruple suppressing plants had lower level of JA-Ile compared with wild type plants, suggesting functional redundancy of the same clade of GH3 family. Furthermore, the group I GH3 family genes positively mediated rice resistance to bacterial pathogen Xoo through modulating JA homeostasis and regulating transcription pattern of JA-responsive genes.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Homeostasis; Isoleucine; Ligases; Multigene Family; Oryza; Oxylipins; Plant Diseases; Plants, Genetically Modified; Transcription, Genetic; Xanthomonas

Arabidopsis MAP kinase 4 (MPK4) has been proposed to be a negative player in plant immunity, and it is also activated by pathogen-associated molecular patterns (PAMPs), such as flg22. The molecular mechanisms by which MPK4 is activated and regulates plant defense remain elusive. In this study, we investigated Arabidopsis defense against a bacterial pathogen Pseudomonas syringae pv tomato ( Pst) DC3000 when Brassica napus MPK4 ( BnMPK4) is overexpressed. We showed an increase in pathogen resistance and suppression of jasmonic acid (JA) signaling in the BnMPK4 overexpressing (OE) plants. We also showed that the OE plants have increased sensitivity to flg22-triggered reactive oxygen species (ROS) burst in guard cells, which resulted in enhanced stomatal closure compared to wild-type (WT). During flg22 activation, dynamic phosphorylation events within and outside of the conserved TEY activation loop were observed. To elucidate how BnMPK4 functions during the defense response, we used immunoprecipitation coupled with mass spectrometry (IP-MS) to identify BnMPK4 interacting proteins in the absence and presence of flg22. Quantitative proteomic analysis revealed a shift in the MPK4-associated protein network, providing insight into the molecular functions of MPK4 at the systems level.

Topics: Arabidopsis; Arabidopsis Proteins; Bacterial Proteins; Cyclopentanes; Disease Resistance; Flagellin; Gene Expression Regulation, Plant; Mitogen-Activated Protein Kinases; Oxylipins; Phosphorylation; Plant Diseases; Plant Immunity; Protein Interaction Maps; Pseudomonas syringae; Reactive Oxygen Species

A U-box E3 ubiquitin ligase GhPUB17 is inhibited by GhCyP3 with antifungal activity and acts as a negative regulator involved in cotton resistance to Verticillium dahliae. E3 ubiquitin ligases, the key component enzymes of the ubiquitin-proteasome system, which contains the most diverse structural and functional members involved in the determination of target specificity and the regulation of metabolism, have been well documented in previous studies. Here, we identify GhPUB17, a U-box E3 ligase in cotton that has ubiquitination activity and is involved in the cotton immune response to Verticillium dahliae. The expression level of GhPUB17 is downregulated in the ssn mutant with a constitutively activated immune response (Sun et al., Nat Commun 5:5372, 2014). Infection with V. dahliae or exogenous hormone treatment, including jasmonic acid and salicylic acid, significantly upregulated GhPUB17 in cotton roots, which suggested a possible role for this E3 ligase in the plant immune response to pathogens. Moreover, GhPUB17-knockdown cotton plants are more resistant to V. dahliae, whereas GhPUB17-overexpressing plants are more susceptible to the pathogen, which indicated that GhPUB17 is a negative regulator of cotton resistance to V. dahliae. A yeast two-hybrid (Y2H) assay identified GhCyP3 as a protein that interacts with GhPUB17, and this finding was confirmed by further protein interaction assays. The downregulation of GhCyP3 in cotton seedlings attenuated the plants' resistance to V. dahliae. In addition, GhCyP3 showed antifungal activity against V. dahliae, and the E3 ligase activity of GhPUB17 was repressed by GhCyP3 in vitro. These results suggest that GhPUB17 negatively regulates cotton immunity to V. dahliae and that the antifungal protein GhCyP3 likely interacts with and inhibits the ligase activity of GhPUB17 and plays an important role in the cotton-Verticillium interaction.

Topics: Antifungal Agents; Cyclopentanes; Cyclophilins; Cytochrome P450 Family 3; Disease Resistance; Down-Regulation; Gene Expression Regulation, Plant; Gene Knockdown Techniques; Gene Silencing; Gossypium; Oxylipins; Plant Diseases; Plant Immunity; Plant Proteins; Plant Roots; Recombinant Proteins; Salicylic Acid; Ubiquitin-Protein Ligases; Ubiquitination; Verticillium

Herbivore-induced plant volatiles prime plant defenses and resistance, but how they are integrated into early defense signaling and whether a causal relationship exists between volatile defense priming and herbivore resistance is unclear. Here, we investigated the impact of indole, a common herbivore-induced plant volatile and modulator of many physiological processes in plants, bacteria, and animals, on early defense signaling and herbivore resistance in rice (

Topics: Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Herbivory; Indoles; Mitogen-Activated Protein Kinases; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Signal Transduction; Spodoptera

Trichoderma spp. are effective biocontrol agents for many plant pathogens, thus the mechanism of Trichoderma-induced plant resistance is not fully understood. In this study, a novel Trichoderma strain was identified, which could promote plant growth and reduce the disease index of gray mold caused by Botrytis cinerea in cucumber. To assess the impact of Trichoderma inoculation on the plant response, a multi-omics approach was performed in the Trichoderma-inoculated cucumber plants through the analyses of the plant transcriptome, proteome, and phytohormone content.. A novel Trichoderma strain was identified by morphological and molecular analysis, here named T. longibrachiatum H9. Inoculation of T. longibrachiatum H9 to cucumber roots promoted plant growth in terms of root length, plant height, and fresh weight. Root colonization of T. longibrachiatum H9 in the outer layer of epidermis significantly inhibited the foliar pathogen B. cinerea infection in cucumber. The plant transcriptome and proteome analyses indicated that a large number of differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were identified in cucumber plants 96 h post T. longibrachiatum H9 inoculation. Up-regulated DEGs and DEPs were mainly associated with defense/stress processes, secondary metabolism, and phytohormone synthesis and signaling, including jasmonic acid (JA), ethylene (ET) and salicylic acid (SA), in the T. longibrachiatum H9-inoculated cucumber plants in comparison to untreated plants. Moreover, the JA and SA contents significantly increased in cucumber plants with T. longibrachiatum H9 inoculation.. Application of T. longibrachiatum H9 to the roots of cucumber plants effectively promoted plant growth and significantly reduced the disease index of gray mold caused by B. cinerea. The analyses of the plant transcriptome, proteome and phytohormone content demonstrated that T. longibrachiatum H9 mediated plant systemic resistance to B. cinerea challenge through the activation of signaling pathways associated with the phytohormones JA/ET and SA in cucumber.

Topics: Biomarkers; Cucumis sativus; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Proteomics; Salicylic Acid; Signal Transduction; Transcriptome; Trichoderma

Ultraviolet radiation (UV) is an important modulator of plant defenses against biotic stresses. We have recently described that different supplemental UV exposure times and irradiance intensities enhanced tomato (Solanum lycopersicum) resistance to Western flower thrips (Frankliniella occidentalis). UV increased jasmonic acid-isoleucine (JA-Ile) and salicylic acid (SA) levels, as well as the expression of JA- and SA-responsive genes, before thrips herbivory. Here we report how UV affects tomato defense responses upon thrips infestation, and resistance to pathogens that are susceptible to the activation of SA-associated defenses. Our experiments reveal that, at 7 days after thrips infestation, UV did not enhance the levels of jasmonates, auxin or abscisic acid. UV also did not affect the expression of JA-responsive genes in the cultivar Moneymaker, the jasmonate deficient mutant def-1, the type-VI trichome deficient mutant od-2, or their wild-type Castlemart. However, UV strongly activated SA-associated defense responses in def-1 after thrips infestation. Further bioassays showed that UV increased def-1 resistance to the hemi-biotrophic bacterial pathogen Pseudomonas syringae pv. tomato DC3000, which is susceptible to SA-mediated defenses. Our results suggest that UV might enhance tomato resistance to this pathogen in the JA deficient genotype through the activation of SA defenses.

Topics: Abscisic Acid; Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Indoleacetic Acids; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Plants, Genetically Modified; Pseudomonas syringae; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Thysanoptera; Ultraviolet Rays

Feeding by insect herbivores such as caterpillars and aphids induces plant resistance mechanisms that are mediated by the phytohormones jasmonic acid (JA) and salicylic acid (SA). These phytohormonal pathways often crosstalk. Besides phytohormones, methyl-D-erythriol-2,4-cyclodiphosphate (MEcPP), the penultimate metabolite in the methyl-D-erythritol-4-phosphate pathway, has been speculated to regulate transcription of nuclear genes in response to biotic stressors such as aphids. Here, we show that MEcPP uniquely enhances the SA pathway without attenuating the JA pathway. Arabidopsis mutant plants that accumulate high levels of MEcPP (hds3) are highly resistant to the cabbage aphid (Brevicoryne brassicae), whereas resistance to the large cabbage white caterpillar (Pieris brassicae) remains unaltered. Thus, MEcPP is a distinct signalling molecule that acts beyond phytohormonal crosstalk to induce resistance against the cabbage aphid in Arabidopsis. We dissect the molecular mechanisms of MEcPP mediating plant resistance against the aphid B. brassicae. This shows that MEcPP induces the expression of genes encoding enzymes involved in the biosynthesis of several primary and secondary metabolic pathways contributing to enhanced resistance against this aphid species. A unique ability to regulate multifaceted molecular mechanisms makes MEcPP an attractive target for metabolic engineering in Brassica crop plants to increase resistance to cabbage aphids.

Topics: Animals; Aphids; Arabidopsis; Arabidopsis Proteins; Brassica; Cyclopentanes; Cytochrome P-450 Enzyme System; Disease Resistance; Erythritol; Gene Expression Regulation, Plant; Glucosinolates; Metabolic Networks and Pathways; Metabolome; Oxylipins; Plant Growth Regulators; Salicylic Acid; Secondary Metabolism; Signal Transduction; Sugar Phosphates; Transcription Factors

Tomato spotted wilt virus (TSWV) causes major losses of many crops worldwide. Several strategies have been attempted to control disease caused by TSWV. However, many challenges for the effective control of this disease remain. A promising approach is the use of abiotic or biotic inducers to enhance plant resistance to pathogens. We screened a diterpenoid compound from Wedelia trilobata, 3α-Angeloyloxy-9β-hydroxy-ent-kaur-16-en-19-oic acid (AHK), which had higher curative and protective effects against TSWV than the ningnanmycin control. The rapid initiation of the expression of all the TSWV genes was delayed by more than 1d in the curative assay, and the expression of the NSs, NSm and RdRp genes was inhibited. In addition, the replication of all TSWV genes in systemic leaves was inhibited in the protective assay, with an inhibition rate of more than 90%. The concentrations of jasmonic acid (JA) and jasmonic acid isoleucine (JA-ILE) in the AHK-treated and systemic leaves of the treated plants were significantly higher than those observed in the control. The results suggested that AHK can induce systemic resistance in treated plants. The transcription of the NtCOI1 gene, a key gene in the JA pathway, was significantly higher in both the inoculated and systemic leaves of the AHK-treated plants compared to the control. The AHK-induced resistance to TSWV in Nicotiana benthamiana could be eliminated by VIGS-mediated silencing of the NtCOI1 gene. These results indicated that AHK can activate the JA pathway and induce systemic resistance to TSWV infection.

Topics: Cyclopentanes; Disease Resistance; Diterpenes; Gene Expression; Nicotiana; Oxylipins; Plant Diseases; Plant Leaves; Signal Transduction; Tospovirus; Wedelia

A halotolerant rhizobacteria, Klebsiella species (referred to MBE02), was identified that had a growth stimulation effect on peanut. To gain mechanistic insights into how molecular components were reprogrammed during the interaction of MBE02 and peanut roots, we performed deep RNA-sequencing. In total, 1260 genes were differentially expressed: 979 genes were up-regulated, whereas 281 were down-regulated by MBE02 treatment as compared to uninoculated controls. A large component of the differentially regulated genes were related to phytohormone signalling. This included activation of a significant proportion of genes involved in jasmonic acid, ethylene and pathogen-defense signalling, which indicated a role of MBE02 in modulating plant immunity. In vivo and in vitro pathogenesis assays demonstrated that MBE02 treatment indeed provide fitness benefits to peanut against Aspergillus infection under controlled as well as field environment. Further, MBE02 directly reduced the growth of a wide range of fungal pathogens including Aspergillus. We also identified possible molecular components involved in rhizobacteria-mediated plant protection. Our results show the potential of MBE02 as a biocontrol agent in preventing infection against several fungal phytopathogens.

Topics: Arabidopsis; Arachis; Cyclopentanes; Disease Resistance; Ethylenes; Fungi; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Plant; Klebsiella; Mycoses; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Roots; RNA-Seq; Signal Transduction

MYB15 promoter of Vitis quinquangularis has potential as a target for disease resistance breeding, and its involvement in PTI is associated with a range of defense mechanisms. China is a center of origin for Vitis and is home to diverse wild Vitis genotypes, some of which show superior pathogen resistance, although the underlying molecular basis for this has not yet been elucidated. In the current study, we identified a transcription factor, MYB15, from the Chinese wild grape, Vitis quinquangularis, whose promoter region (pVqMYB15) was shown to be induced by basal immunity (also called PAMP-triggered immunity, PTI) triggered by flg22, following heterologous expression in Nicotiana benthamiana and homologous expression in grapevine. By analyzing the promoter structure and activity, we identified a unique 283 bp sequence that plays a key role in the activation of basal immunity. In addition, we showed that activation of the MYB15 promoter correlates with differences in the expression of MYB15 and RESVERATROL SYNTHASE (RS) induced by the flg22 elicitor. We further tested whether the MYB15 induction triggered by flg22 was consistent with MYB15 and RS expression following inoculation with Plasmopara viticola in grape (V. quinquangularis and Vitis vinifera) leaves. Mapping upstream signals, we found that calcium influx, an RboH-dependent oxidative burst, an MAPK cascade, and jasmonate and salicylic acid co-contributed to flg22-triggered pVqMYB15 activation. Our data suggest that the MYB15 promoter has potential as a target for disease resistance breeding, and its involvement in PTI is associated with a range of defense mechanisms.

Topics: China; Cyclopentanes; Disease Resistance; Oomycetes; Oxylipins; Plant Breeding; Plant Diseases; Plant Growth Regulators; Plant Proteins; Promoter Regions, Genetic; Salicylic Acid; Transcription Factors; Vitis

Systemic acquired resistance (SAR) induction is one of the primary defence mechanisms of plants against a broad range of pathogens. It can be induced by infectious agents or by synthetic molecules, such as benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH). SAR induction is associated with increases in salicylic acid (SA) accumulation and expression of defence marker genes (e.g., phenylalanine ammonia-lyase

Topics: Cyclopentanes; Disease Resistance; Ethylenes; Nicotiana; Oxylipins; Salicylic Acid; Thiadiazoles; Tobamovirus

Herein, the class II hydrophobin gene HFBII-4 was cloned from the biocontrol agent Trichoderma asperellum ACCC30536 and recombinant rHFBII-4 was expressed in Pichia pastoris GS115. Treatment of Populus davidiana × P. alba var. pyramidalis (PdPap poplar) with rHFBII-4 altered the expression levels of genes in the auxin, salicylic acid (SA), and jasmonic acid (JA) signal transduction pathways. Polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) enzyme activities were induced with rHFBII-4. Evans Blue and nitro blue tetrazolium (NBT) staining indicated that cell membrane permeability and reactive oxygen species were lower in the leaves of plants treated with rHFBII-4. The chlorophyll content was higher than that of control at 2-5 days after treatment. Furthermore, poplar seedlings were inoculated with Alternaria alternata, disease symptoms were observed. The diseased area was smaller in leaves induced with rHFBII-4 compared with control. In summary, rHFBII-4 enhances resistance to A. alternata.

Topics: Alternaria; Cyclopentanes; Disease Resistance; Fungal Proteins; Gene Expression Regulation, Fungal; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Populus; Trichoderma

INDETERMINATE DOMAIN (IDD)/BIRD proteins belong to a highly conserved plant-specific group of transcription factors with dedicated functions in plant physiology and development. Here, we took advantage of the chimeric repressor gene-silencing technology (CRES-T, SRDX) to widen our view on the role of IDD4/IMPERIAL EAGLE and IDD family members in plant immunity. The hypomorphic idd4SRDX lines are compromised in growth and show a robust autoimmune phenotype. Hormonal measurements revealed the concomitant accumulation of salicylic acid and jasmonic acid suggesting that IDDs are involved in regulating the metabolism of these biotic stress hormones. The analysis of immunity-pathways showed enhanced activation of immune MAP kinase-signaling pathways, the accumulation of hydrogen peroxide and spontaneous programmed cell death. The transcriptome of nonelicited idd4SRDX lines can be aligned to approximately 40% of differentially expressed genes (DEGs) in flg22-treated wild-type plants. The pattern of DEGs implies IDDs as pivotal repressors of flg22-dependent gene induction. Infection experiments showed the increased resistance of idd4SRDX lines to Pseudomonas syringae and Botrytis cinerea implying a function of IDDs in defense adaptation to hemibiotrophs and necrotrophs. Genome-wide IDD4 DNA-binding studies (DAP-SEQ) combined with DEG analysis of idd4SRDX lines identified IDD4-regulated functional gene clusters that contribute to plant growth and development. In summary, we discovered that the expression of idd4SRDX activates a wide range of defense-related traits opening up the possibility to apply idd4SRDX as a powerful tool to stimulate innate immunity in engineered crops.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Homeostasis; MAP Kinase Signaling System; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Pseudomonas syringae; Repressor Proteins; Salicylic Acid

In rice, Hd3a, GF14 and OsFD1 proteins, forming florigen activation complex, are key components in flowering time regulation. GF14 genes in rice response to biotic and abiotic stress has also been well addressed. The role of GF14e in rice defense has been well studied. However, whether Hd3a and OsFD1 play roles in defense is unclear. In present study, we identified that Hd3a and OsFD1 expression is repressed by Xoo and JA, and validated that Hd3a and OsFD1 negatively regulate resistance to Xanthomonas oryzae pv. oryzae (Xoo) and Xanthomonas oryzae pv. oryzicola (Xoc). hd3a and osfd1 mutants increase resistance to Xoo and Xoc, and activate JA responsive genes expression. Our data also demonstrate that OsFD1 binds to the promoters of and activates the expression of JAZ genes; Hd3a, cooperating with GF14e, promotes OsFD1 action on JAZ gene expression. The functional confirmation of Hd3a and OsFD1 in rice defense makes them to be promising targets in molecular rice breeding.

Topics: Cyclopentanes; Disease Resistance; Flagellin; Gene Expression Regulation, Plant; Mutation; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Xanthomonas

The elicitor Hrip1 isolated from necrotrophic fungus Alternaria tenuissima, could induce systemic acquired resistance in tobacco to enhance resistance to tobacco mosaic virus. In the present study, we found that the transgenic lines of Hrip1-overexpression in wild type (WT) Arabidopsis thaliana were more resistant to Spodoptera exigua and were early bolting and flowering than the WT. A profiling of transcription assay using digital gene expression profiling was used for transgenic and WT Arabidopsis thaliana. Differentially expressed genes including 40 upregulated and three downregulated genes were identified. In transgenic lines of Hrip1-overexpression, three genes related to jasmonate (JA) biosynthesis were significantly upregulated, and the JA level was found to be higher than WT. Two GDSL family members (GLIP1 and GLIP4) and pathogen-related gene, which participated in pathogen defense action, were upregulated in the transgenic line of Hrip1-overexpression. Thus, Hrip1 is involved in affecting the flower bolting time and regulating endogenous JA biosynthesis and regulatory network to enhance resistance to insect.

Topics: Animals; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Flowers; Gene Expression Regulation, Plant; Oxylipins; Photoperiod; Plant Diseases; Plants, Genetically Modified; Reproducibility of Results; Spodoptera

Arabidopsis thaliana mlo3 mutant plants are not affected in pathogen infection phenotypes but-reminiscent of mlo2 mutant plants-exhibit spontaneous callose deposition and signs of early leaf senescence. The family of Mildew resistance Locus O (MLO) proteins is best known for its profound effect on the outcome of powdery mildew infections: when the appropriate MLO protein is absent, the plant is fully resistant to otherwise virulent powdery mildew fungi. However, most members of the MLO protein family remain functionally unexplored. Here, we investigate Arabidopsis thaliana MLO3, the closest relative of AtMLO2, AtMLO6 and AtMLO12, which are the Arabidopsis MLO genes implicated in the powdery mildew interaction. The co-expression network of AtMLO3 suggests association of the gene with plant defense-related processes such as salicylic acid homeostasis. Our extensive analysis shows that mlo3 mutants are unaffected regarding their infection phenotype upon challenge with the powdery mildew fungi Golovinomyces orontii and Erysiphe pisi, the oomycete Hyaloperonospora arabidopsidis, and the bacterial pathogen Pseudomonas syringae (the latter both in terms of basal and systemic acquired resistance), indicating that the protein does not play a major role in the response to any of these pathogens. However, mlo3 genotypes display spontaneous callose deposition as well as signs of early senescence in 6- or 7-week-old rosette leaves in the absence of any pathogen challenge, a phenotype that is reminiscent of mlo2 mutant plants. We hypothesize that de-regulated callose deposition in mlo3 genotypes might be the result of a subtle transient aberration of salicylic acid-jasmonic acid homeostasis during development.

Topics: Arabidopsis; Arabidopsis Proteins; Ascomycota; Calmodulin-Binding Proteins; Cyclopentanes; Disease Resistance; Genotype; Glucans; Homeostasis; Mutation; Oomycetes; Oxylipins; Phenotype; Plant Diseases; Plant Growth Regulators; Plant Leaves; Pseudomonas syringae; Salicylic Acid

Topics: Arabidopsis; Arabidopsis Proteins; Cold-Shock Response; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Hydrogen Peroxide; Oxylipins; Pseudomonas syringae; Salicylic Acid

Several elicitors, stimulating induced resistance mechanisms, have potential in preventing or mitigating pathogen infections. Some of these compounds, triggering the production of jasmonic acid (JA), a precursor of herbivore-induced plant volatiles, could also play a central role in indirect resistance to pest species, by improving beneficial arthropod performance, and necrotrophic pathogens. In the current work, Trichoderma gamsii/T. asperellum and silica gel treatments - alone and in combination - were studied to evaluate the plant defence mechanism on grapevines (Vitis vinifera L.) by laboratory and field trials. JA production level was measured before and after Plasmopara viticola infection on potted vines. JA production induced by silica gel was higher than that caused by Trichoderma before infection. In Trichoderma-treated plants, JA production increased after P. viticola inoculation. In vineyard field trials, Mymaridae (Hymenoptera: Chalcidoidea) showed higher captures in transparent sticky traps on silica gel-treated plants, in comparison with control. On the other hand, no significant attraction was detected for Ichneumonoidea and other Chalcidoidea in silica gel and T. gamsii/T. asperellum-treated plants. The potential effects of elicitors are discussed, in the frame of attract and reward strategy.

Topics: Animals; Cyclopentanes; Disease Resistance; Oomycetes; Oxylipins; Plant Diseases; Silica Gel; Trichoderma; Vitis; Wasps

Topics: Cyclopentanes; Disease Resistance; Esterification; Gene Ontology; Oryza; Oxylipins; Plant Growth Regulators; Plant Proteins; Proteomics; Stress, Physiological

Harpin proteins secreted by plant-pathogenic gram-negative bacteria induce diverse plant defenses against different pathogens. Harpin-induced 1 (HIN1) gene highly induced in tobacco after application of Harpin protein is involved in a common plant defense pathway. However, the role of HIN1 against Tobacco mosaic virus (TMV) remains unknown. In this study, we functionally characterized the Nicotiana benthamiana HIN1 (NbHIN1) gene and generated the transgenic tobacco overexpressing the NbHIN1 gene. In a subcellular localization experiment, we found that NbHIN1 localized in the plasma membrane and cytosol. Overexpression of NbHIN1 did not lead to observed phenotype compared to wild type tobacco plant. However, the NbHIN1 overexpressing tobacco plant exhibited significantly enhanced resistance to TMV infection. Moreover, RNA-sequencing revealed the transcriptomic profiling of NbHIN1 overexpression and highlighted the primary effects on the genes in the processes related to biosynthesis of amino acids, plant-pathogen interaction and RNA transport. We also found that overexpression of NbHIN1 highly induced the expression of NbRAB11, suggesting that jasmonic acid signaling pathway might be involved in TMV resistance. Taken together, for the first time we demonstrated that overexpressing a pathogenesis-related gene NbHIN1 in N. benthamiana significantly enhances the TMV resistance, providing a potential mechanism that will enable us to engineer tobacco with improved TMV resistance in the future.

Topics: Blotting, Western; Cloning, Molecular; Cyclopentanes; Disease Resistance; Genes, Plant; Microscopy, Confocal; Nicotiana; Oxylipins; Phylogeny; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Real-Time Polymerase Chain Reaction; Signal Transduction; Tobacco Mosaic Virus; Two-Hybrid System Techniques

Xanthomonas campestris pv. campestris (Xcc)- responsive soluble and cell wall-bound hydroxycinnamic acids (HAs) and flavonoids accumulation in relation to hormonal changes in two Brassica napus cultivars contrasting disease susceptibility were interpreted with regard to the disease resistance. At 14-day post inoculation with Xcc, disease resistance in cv. Capitol was distinguished by an accumulation of specific (HAs) and flavonoids particularly in cell-wall bound form, and was characterized by higher endogenous jasmonic acid (JA) resulting in a decrease of JA-based balance with other hormones, as well as enhanced expression of JA signaling that was concurrently based on upregulation of PAP1 (production of anthocyanin pigment 1), MYB transcription factor, and phenylpropanoid biosynthetic genes. Fourier transform infrared spectra confirmed higher amounts of esterified phenolic acids in cv. Capitol. These results indicate that enhanced JA levels and signaling in resistant cultivar was associated with a higher accumulation of HAs and flavonoids, particularly in the cell wall-bound form, and vice versa in the susceptible cultivar (cv. Mosa) with enhanced SA-, ABA-, and CK- levels and signaling. Thus the JA-mediated phenolic metabolites accumulation is an important feature for the management and breeding program to develop disease-resistant B. napus cultivar.

Topics: Brassica napus; Cell Wall; Coumaric Acids; Cyclopentanes; Disease Resistance; Disease Susceptibility; Flavonoids; Lipid Peroxidation; Microscopy, Electron, Scanning; Oxylipins; Peptide Hydrolases; Phenols; Plant Diseases; Plant Growth Regulators; Plant Leaves; Reactive Oxygen Species; Xanthomonas campestris

Jasmonic acid (JA) is a plant hormone that plays an important role in the defense response and stable growth of rice. In this study, we investigated the role of the JA-responsive valine-glutamine (VQ)-motif-containing protein OsVQ13 in JA signaling in rice. OsVQ13 was primarily located in the nucleus and cytoplasm. The transgenic rice plants overexpressing

Topics: Cyclopentanes; Disease Resistance; Edible Grain; Mitogen-Activated Protein Kinases; Oryza; Oxylipins; Plant Proteins; Signal Transduction; Transcription Factors; Xanthomonas

Insects have evolved effectors to conquer plant defense. Most known insect effectors are isolated from sucking insects, and examples from chewing insects are limited. Moreover, the targets of insect effectors in host plants remain unknown. Here, we address a chewing insect effector and its working mechanism. Cotton bollworm (

Topics: Animals; Arabidopsis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Host-Parasite Interactions; Moths; Oxylipins; Plant Diseases; Plant Leaves; Signal Transduction

Interplay of hormones with reactive oxygen species (ROS) fine-tunes the response of plants to stress; however, the crosstalk between brassinosteroids (BRs) and ROS in nematode resistance is unclear. In this study, we found that low BR biosynthesis or lack of BR receptor increased, whilst exogenous BR decreased the susceptibility of tomato plants to Meloidogyne incognita. Hormone quantification coupled with hormone mutant complementation experiments revealed that BR did not induce the defence response by triggering salicylic acid (SA), jasmonic acid/ethylene (JA/ET) or abscisic acid (ABA) signalling pathway. Notably, roots of BR-deficient plants had decreased apoplastic ROS accumulation, transcript of RESPIRATORY BURST OXIDASE HOMOLOG1 (RBOH1) and WHITEFLY INDUCED1 (WFI1), and reduced activation of mitogen-activated protein kinase 1/2 (MPK1/2) and MPK3. Silencing of RBOH1, WFI1, MPK1, MPK2 and MPK3 all increased the root susceptibility to nematode and attenuated BR-induced resistance against the nematode. Significantly, suppressed transcript of RBOH1 compromised BR-induced activation of MPK1/2 and MPK3. These results strongly suggest that RBOH-dependent MPK activation is involved in the BR-induced systemic resistance against the nematode.

Topics: Abscisic Acid; Animals; Brassinosteroids; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Mitogen-Activated Protein Kinases; NADPH Oxidases; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Tylenchoidea

Erwinia amylovora is the causal agent of the fire blight disease in some plants of the Rosaceae family. The non-host plant Arabidopsis serves as a powerful system for the dissection of mechanisms of resistance to E. amylovora. Although not yet known to mount gene-for-gene resistance to E. amylovora, we found that Arabidopsis activated strong defence signalling mediated by salicylic acid (SA), with kinetics and amplitude similar to that induced by the recognition of the bacterial effector avrRpm1 by the resistance protein RPM1. Genetic analysis further revealed that SA signalling, but not signalling mediated by ethylene (ET) and jasmonic acid (JA), is required for E. amylovora resistance. Erwinia amylovora induces massive callose deposition on infected leaves, which is independent of SA, ET and JA signalling and is necessary for E. amylovora resistance in Arabidopsis. We also observed tumour-like growths on E. amylovora-infected Arabidopsis leaves, which contain enlarged mesophyll cells with increased DNA content and are probably a result of endoreplication. The formation of such growths is largely independent of SA signalling and some E. amylovora effectors. Together, our data reveal signalling requirements for E. amylovora-induced disease resistance, callose deposition and cell fate change in the non-host plant Arabidopsis. Knowledge from this study could facilitate a better understanding of the mechanisms of host defence against E. amylovora and eventually improve host resistance to the pathogen.

Topics: Arabidopsis; Cell Proliferation; Cyclopentanes; Disease Resistance; Erwinia amylovora; Ethylenes; Glucans; Ions; Mutation; Oxylipins; Plant Diseases; Salicylic Acid; Signal Transduction

WRKY transcription factors are known to participate in the defence responses of higher plants. However, little is known about the roles of such proteins, especially regarding their functions in the resistance of oilseed rape (Brassica napus) to Sclerotinia sclerotiorum, a necrotrophic fungal pathogen that causes stem rot. In this study, we identified BnWRKY33 as a S. sclerotiorum-responsive gene that positively regulates resistance to this pathogen by enhancing the expression of genes involved in camalexin synthesis and genes regulated by salicylic acid (SA) and jasmonic acid (JA). We also identified a S. sclerotiorum-responsive region in the promoter of BnWRKY33, which we revealed to be a relatively conserved W-box region in the promoters of homologous genes in different species. Using this S. sclerotiorum-responsive region as bait in a yeast one-hybrid assay, we identified another WRKY transcription factor, BnWRKY15, and observed that both BnWRKY15 and BnWRKY33 could bind to this region. In addition, BnWRKY15 overexpression simultaneously increased the susceptibility of B. napus to S. sclerotiorum and down-regulated BnWRKY33 after different durations of infection. Furthermore, BnWRKY15, which contains a transcriptional repression domain, exhibited reduced transactivation ability and could reduce the transactivation ability of BnWRKY33 in Arabidopsis protoplast assays. Therefore, we suggest that the increased susceptibility of BnWRKY15-overexpressing plants results from reduced BnWRKY33 expression, which is due to the inhibition of BnWRKY33 transcriptional activation by BnWRKY15.

Topics: Arabidopsis; Arabidopsis Proteins; Ascomycota; Brassica napus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Promoter Regions, Genetic; Salicylic Acid; Transcription Factors; Two-Hybrid System Techniques

Ferredoxins, the major distributors for electrons to various acceptor systems in plastids, contribute to redox regulation and antioxidant defence in plants. However, their function in plant immunity is not fully understood. In this study, we show that the expression of the major leaf ferredoxin gene Fd2 is suppressed by Pseudomonas syringae pv. tomato (Pst) DC3000 infection, and that knockout of Fd2 (Fd2-KO) in Arabidopsis increases the plant's susceptibility to both Pst DC3000 and Golovinomyces cichoracearum. On Pst DC3000 infection, the Fd2-KO mutant accumulates increased levels of jasmonic acid and displays compromised salicylic acid-related immune responses. Fd2-KO also shows defects in the accumulation of reactive oxygen species induced by pathogen-associated molecular pattern-triggered immunity. However, Fd2-KO shows enhanced R-protein-mediated resistance to Pst DC3000/AvrRpt2 infection, suggesting that Fd2 plays a negative role in effector-triggered immunity. Furthermore, Fd2 interacts with FIBRILLIN4 (FIB4), a harpin-binding protein localized in chloroplasts. Interestingly, Fd2, but not FIB4, localizes to stromules that extend from chloroplasts. Taken together, our results demonstrate that Fd2 plays an important role in plant immunity.

Topics: Arabidopsis; Cyclopentanes; Disease Resistance; Ferredoxins; Oxylipins; Plant Diseases; Plant Immunity; Plant Leaves; Reactive Oxygen Species; Salicylic Acid

Bacillus cereus AR156 (AR156) is a plant growth-promoting rhizobacterium capable of inducing systemic resistance to Pseudomonas syringae pv. tomato in Arabidopsis thaliana. Here, we show that, when applied to Arabidopsis leaves, AR156 acted similarly to flg22, a typical pathogen-associated molecular pattern (PAMP), in initiating PAMP-triggered immunity (PTI). AR156-elicited PTI responses included phosphorylation of MPK3 and MPK6, induction of the expression of defense-related genes PR1, FRK1, WRKY22, and WRKY29, production of reactive oxygen species, and callose deposition. Pretreatment with AR156 still significantly reduced P. syringae pv. tomato multiplication and disease severity in NahG transgenic plants and mutants sid2-2, jar1, etr1, ein2, npr1, and fls2. This suggests that AR156-induced PTI responses require neither salicylic acid, jasmonic acid, and ethylene signaling nor flagella receptor kinase FLS2, the receptor of flg22. On the other hand, AR156 and flg22 acted in concert to differentially regulate a number of AGO1-bound microRNAs that function to mediate PTI. A full-genome transcriptional profiling analysis indicated that AR156 and flg22 activated similar transcriptional programs, coregulating the expression of 117 genes; their concerted regulation of 16 genes was confirmed by real-time quantitative polymerase chain reaction analysis. These results suggest that AR156 activates basal defense responses to P. syringae pv. tomato in Arabidopsis, similarly to flg22.

Topics: Arabidopsis; Arabidopsis Proteins; Bacillus cereus; Cyclopentanes; Disease Resistance; Ethylenes; Flagellin; Gene Expression Profiling; Gene Expression Regulation, Plant; MicroRNAs; Oxylipins; Plant Immunity; Pseudomonas syringae; RNA, Messenger; Salicylic Acid; Transcription, Genetic

Coevolution has shaped the molecular basis of an extensive number of defense mechanisms in plant-pathogen interactions. Phytophthora parasitica, a hemibiothrophic oomycete pathogen and the causal agent of citrus root rot and gummosis, interacts differently with Citrus sunki and Poncirus trifoliata, two commonly favored citrus rootstocks that are recognized as susceptible and resistant, respectively, to P. parasitica. The molecular core of these interactions remains elusive. Here, we provide evidence on the defense strategies employed by both susceptible and resistant citrus rootstocks, in parallel with P. parasitica deployment of effectors. Time course expression analysis (quantitative real-time polymerase chain reaction) of several defense-related genes were evaluated during i) plant disease development, ii) necrosis, and iii) pathogen effector gene expression. In C. sunki, P. parasitica deploys effectors, including elicitins, NPP1 (necrosis-inducing Phytophthora protein 1), CBEL (cellulose-binding elicitor and lectin activity), RxLR, and CRN (crinkler), and, consequently, this susceptible plant activates its main defense signaling pathways that result in the hypersensitive response and necrosis. Despite the strong plant-defense response, it fails to withstand P. parasitica invasion, confirming its hemibiothrophic lifestyle. In Poncirus trifoliata, the effectors were strongly expressed, nevertheless failing to induce any immunity manipulation and disease development, suggesting a nonhost resistance type, in which the plant relies on preformed biochemical and anatomical barriers.

Topics: Citrus; Cluster Analysis; Cyclopentanes; Disease Resistance; Disease Susceptibility; Ethylenes; Gene Expression Regulation, Plant; Gene Regulatory Networks; Genes, Plant; Hydrogen Peroxide; Linear Models; Models, Biological; Oxylipins; Phytophthora; Plant Diseases; Poncirus; Salicylic Acid

We isolated previously several Arabidopsis thaliana mutants with constitutive expression of the early microbe-associated molecular pattern-induced gene ATL2, named eca (expresión constitutiva de ATL2). Here, we further explored the interaction of eca mutants with pest and pathogens. Of all eca mutants, eca2 was more resistant to a fungal pathogen (Botrytis cinerea) and a bacterial pathogen (Pseudomonas syringae) as well as to a generalist herbivorous insect (Spodoptera littoralis). Permeability of the cuticle is increased in eca2; chemical characterization shows that eca2 has a significant reduction of both cuticular wax and cutin. Additionally, we determined that eca2 did not display a similar compensatory transcriptional response, compared with a previously characterized cuticular mutant, and that resistance to B. cinerea is mediated by the priming of the early and late induced defense responses, including salicylic acid- and jasmonic acid-induced genes. These results suggest that ECA2-dependent responses are involved in the nonhost defense mechanism against biotrophic and necrotrophic pathogens and against a generalist insect by modulation and priming of innate immunity and late defense responses. Making eca2 an interesting model to characterize the molecular basis for plant defenses against different biotic interactions and to study the initial events that take place in the cuticle surface of the aerial organs.

Topics: Animals; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; DNA-Binding Proteins; DNA, Plant; Gene Expression Profiling; Gene Expression Regulation, Plant; Genome, Plant; Herbivory; Insecta; Membrane Lipids; Models, Biological; Mutation; Oxylipins; Plant Diseases; Plant Epidermis; Pseudomonas syringae; Waxes

Damaged cells send various signals to stimulate defense responses. Recent identification and genetic studies of the plant purinoceptor, P2K1 (also known as DORN1), have demonstrated that extracellular ATP is a signal involved in plant stress responses, including wounding, perhaps to evoke plant defense. However, it remains largely unknown how extracellular ATP induces plant defense responses. Here, we demonstrate that extracellular ATP induces plant defense mediated through activation of the intracellular signaling of jasmonate (JA), a well-characterized defense hormone. In Arabidopsis (

Topics: Adenosine Triphosphate; Arabidopsis; Arabidopsis Proteins; Botrytis; Calcium; Cyclopentanes; Disease Resistance; Extracellular Space; Gene Expression Regulation, Plant; Genes, Plant; Nitric Oxide; Oxylipins; Proteasome Endopeptidase Complex; Protein Stability; Proteolysis; Reactive Oxygen Species; Repressor Proteins; Signal Transduction; Up-Regulation

Plants are constantly challenged by a multitude of pathogens and pests, which causes massive yield and quality losses annually. A promising approach to reduce such losses is to enhance the immune system of plants through genetic engineering. Previous work has shown that laccases (p-diphenol:dioxygen oxidoreductase, EC 1.10.3.2) function as lignin polymerization enzymes. Here we demonstrate that transgenic manipulation of the expression of the laccase gene

Topics: Animals; Aphids; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Laccase; Lepidoptera; Lignin; Oxylipins; Plant Diseases; Plant Proteins; Propanols; Verticillium

Stomatal immunity restricts bacterial entry to leaves through the recognition of microbe-associated molecular patterns (MAMPs) by pattern-recognition receptors (PRRs) and downstream abscisic acid and salicylic acid signaling. Through a reverse genetics approach, we characterized the function of the L-type lectin receptor kinase-V.2 (LecRK-V.2) and -VII.1 (LecRK-VII.1). Analyses of interactions with the PRR FLAGELLIN SENSING2 (FLS2) were performed by co-immunoprecipitation and bimolecular fluorescence complementation and whole-cell patch-clamp analyses were used to evaluate guard cell Ca

Topics: Acetates; Amino Acid Sequence; Arabidopsis; Arabidopsis Proteins; Cell Membrane; Cyclopentanes; Disease Resistance; Flagellin; Ion Channel Gating; Mutation; Oxylipins; Plant Diseases; Plant Immunity; Plant Stomata; Protein Binding; Protein Kinases; Protein Serine-Threonine Kinases; Reactive Oxygen Species

Fusarium graminearum is a major pathogen of wheat causing Fusarium head blight (FHB). Its ability to colonize wheat via seedling root infection has been reported recently. Our previous study on Fusarium root rot (FRR) has disclosed histological characteristics of pathogenesis and pathogen defense that mirror processes of spike infection. Therefore, it would be interesting to understand whether genes relevant for FHB resistance are induced in roots. The concept of similar-acting defense mechanisms provides a basis for research at broad Fusarium resistance in crop plants. However, molecular defense responses involved in FRR as well as their relation to spike resistance are unknown. To test the hypothesis of a conserved defense response, a candidate gene expression study was conducted to test the activity of selected prominent FHB defense-related genes in seedling roots, adult plant roots, spikes, and shoots. FRR was examined at seedling and adult plant stages to assess age-related pattern of disease and pathogen resistance. This study offers first evidence for a significant genetic overlap in root and spike defense responses, both in local and distant tissues. The results point to plant development-specific rather than organ-specific determinants of resistance, and suggest roots as an interesting model for studies on wheat-Fusarium interactions.

Topics: Cyclopentanes; Disease Resistance; Fusarium; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Trichothecenes; Triticum

Biosynthesis of the phytohormone jasmonoyl-isoleucine (JA-Ile) requires reduction of the JA precursor 12-oxo-phytodienoic acid (OPDA) by OPDA reductase 3 (OPR3). Previous analyses of the opr3-1 Arabidopsis mutant suggested an OPDA signaling role independent of JA-Ile and its receptor COI1; however, this hypothesis has been challenged because opr3-1 is a conditional allele not completely impaired in JA-Ile biosynthesis. To clarify the role of OPR3 and OPDA in JA-independent defenses, we isolated and characterized a loss-of-function opr3-3 allele. Strikingly, opr3-3 plants remained resistant to necrotrophic pathogens and insect feeding, and activated COI1-dependent JA-mediated gene expression. Analysis of OPDA derivatives identified 4,5-didehydro-JA in wounded wild-type and opr3-3 plants. OPR2 was found to reduce 4,5-didehydro-JA to JA, explaining the accumulation of JA-Ile and activation of JA-Ile-responses in opr3-3 mutants. Our results demonstrate that in the absence of OPR3, OPDA enters the β-oxidation pathway to produce 4,5-ddh-JA as a direct precursor of JA and JA-Ile, thus identifying an OPR3-independent pathway for JA biosynthesis.

Topics: Alleles; Alternaria; Animals; Arabidopsis; Arabidopsis Proteins; Biological Assay; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Homozygote; Insecta; Isoleucine; Mutation; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Roots; Signal Transduction

Land plants protect themselves from ultraviolet-B (UV-B) by accumulating UV-absorbing metabolites, which may also function as anti-insect toxins. Previous studies have shown that UV-B enhances the resistance of different plant species to pierce-sucking pests; however, whether and how UV-B influences plant defense against chewing caterpillars are not well understood. Here we show that UV-B treatment increased Spodoptera litura herbivory-induced jasmonic acid (JA) production in Arabidopsis and thereby Arabidopsis exhibited elevated resistance to S. litura. Using mutants impaired in the biosynthesis of JA and the defensive metabolites glucosinolates (GSs), we show that the UV-B-induced resistance to S. litura is dependent on the JA-regulated GSs and an unidentified anti-insect metabolite(s). Similarly, UV-B treatment also enhanced the levels of JA-isoleucine conjugate and defense-related secondary metabolites in tobacco, rice, and maize after these plants were treated with simulated herbivory of lepidopteran insects; consistently, these plants showed elevated resistance to insect larvae. Using transgenic plants impaired in JA biosynthesis or signaling, we further demonstrate that the UV-B-enhanced defense responses also require the JA pathway in tobacco and rice. Our findings reveal a likely conserved JA-dependent mechanism by which UV-B enhances plant defense against lepidopteran insects.

Topics: Animals; Arabidopsis; Biosynthetic Pathways; Cyclopentanes; Disease Resistance; Herbivory; Lepidoptera; Oryza; Oxylipins; Plant Growth Regulators; Plants; Secondary Metabolism; Signal Transduction; Ultraviolet Rays

The rice pathogenesis-related protein OsPR10a was scarcely expressed in OsCDPK1-silenced (Ri-1) rice, which was highly sensitive to pathogen infection. After inoculating the leaves with bacterial blight (Xanthomonas oryzae pv. oryzae; Xoo), we found that the expression of OsPR10a was up- and down-regulated in OEtr-1 (overexpression of the constitutively active truncated form of OsCDPK1) and Ri-1 rice plants, respectively. OsPR10a and OsCDPK1 showed corresponding expression patterns and were up-regulated in response to the jasmonic acid, salicylic acid and Xoo treatments, and OsPR1 and OsPR4 were significantly up-regulated in OEtr-1. These results suggest that OsCDPK1 may be an upstream regulator involved in rice innate immunity and conferred broad-spectrum of disease resistance. Following the Xoo inoculation, the OEtr-1 and Ri-1 seedlings showed enhanced and reduced disease resistance, respectively. The dihybrid rice Ri-1/OsPR10a-Ox not only bypassed the effect of OsCDPK1 silencing on the susceptibility to Xoo but also showed enhanced disease resistance and, consistent with Ri-1 phenotypes, increased plant height and grain size. Our results reveal that OsCDPK1 plays novel key roles in the cross-talk and mediation of the balance between stress response and development and provides a clue for improving grain yield and disease resistance simultaneously in rice.

Topics: Calcium-Binding Proteins; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Salicylic Acid; Seedlings; Xanthomonas

The brown planthopper (BPH) and white-backed planthopper (WBPH) are the most destructive insect pests of rice, and they pose serious threats to rice production throughout Asia. Thus, there are urgent needs to identify resistance-conferring genes and to breed planthopper-resistant rice varieties. Here we report the map-based cloning and functional analysis of Bph6, a gene that confers resistance to planthoppers in rice. Bph6 encodes a previously uncharacterized protein that localizes to exocysts and interacts with the exocyst subunit OsEXO70E1. Bph6 expression increases exocytosis and participates in cell wall maintenance and reinforcement. A coordinated cytokinin, salicylic acid and jasmonic acid signaling pathway is activated in Bph6-carrying plants, which display broad resistance to all tested BPH biotypes and to WBPH without sacrificing yield, as these plants were found to maintain a high level of performance in a field that was heavily infested with BPH. Our results suggest that a superior resistance gene that evolved long ago in a region where planthoppers are found year round could be very valuable for controlling agricultural insect pests.

Topics: Animals; Cloning, Molecular; Cyclopentanes; Disease Resistance; Exocytosis; Genes, Plant; Insecta; Metabolic Networks and Pathways; Oryza; Oxylipins; Pest Control, Biological; Plant Diseases; Plants, Genetically Modified; Vesicular Transport Proteins

The impacts of rising atmospheric CO

Topics: Arabidopsis; Atmosphere; Carbon Dioxide; Cell Respiration; Cyclopentanes; Disease Resistance; Ice Cover; Light; Metabolomics; Oxylipins; Plant Development; Plant Diseases; Plant Immunity; Reactive Oxygen Species; Salicylic Acid

The plant-specific insert of Solanum tuberosum aspartic proteases (StAP-PSI) has high structural similarity with NK-lysin and granulysin, two saposin-like proteins (SAPLIPs) with antimicrobial activity. Recombinant StAP-PSI and some SAPLIPs show antimicrobial activity against pathogens that affect human and plants. In this work, we transformed Arabidopsis thaliana plants with StAP-PSI encoding sequence with its corresponding signal peptide under the control of the cauliflower mosaic virus (CaMV) 35S promoter. Results obtained show that StAP-PSI significantly enhances Arabidopsis resistance against Botrytis cinerea infection. StAP-PSI is secreted into the leaf apoplast and acts directly against pathogens; thereby complementing plant innate immune responses. Data obtained from real-time PCR assays show that the constitutive expression of StAP-PSI induces the expression of genes that regulate jasmonic acid signalling pathway, such as PDF1.2, in response to infection due to necrotrophic pathogens. On the other hand, according to the data described for other antimicrobial peptides, the presence of the StAP-PSI protein in the apoplast of A. thaliana leaves is responsible for the expression of salicylic acid-associated genes, such as PR-1, irrespective of infection with B. cinerea. These results indicate that the increased resistance demonstrated by A. thaliana plants that constitutively express StAP-PSI owing to B. cinerea infection compared to the wild-type plants is a consequence of two factors, i.e., the antifungal activity of StAP-PSI and the overexpression of A. thaliana defense genes induced by the constitutive expression of StAP-PSI. We suggest that the use of this protein would help in minimizing the ecological and health risks that arise from the use of pesticides. We suggest that the use of this protein would help in minimizing the ecological and health risks that arise from the spreading of resistance of agriculturally important pathogens.

Topics: Arabidopsis Proteins; Aspartic Acid Proteases; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Humans; Oxylipins; Plant Diseases; Plant Leaves; Plants, Genetically Modified; Proteolipids; Pseudomonas syringae; Real-Time Polymerase Chain Reaction; Salicylic Acid; Solanum tuberosum; Transcription Factors

N-decanoyl-homoserine lactone activates plant systemic resistance against Botrytis cinerea in tomato plants, which is largely dependent on jasmonic acid biosynthesis and signal transduction pathways. Rhizosphere bacteria secrete N-acylated-homoserine lactones (AHLs), a type of specialized quorum-sensing signal molecule, to coordinate their population density during communication with their eukaryotic hosts. AHLs behave as low molecular weight ligands that are sensed by plants and promote the host's resistance against foliar pathogens. In this study, we report on N-decanoyl-homoserine lactone (DHL), which is a type of AHL that induces systemic immunity in tomato plants and protects the host organism against the necrotrophic fungus Botrytis cinerea. Upon DHL treatment, tomato endogenous jasmonic acid (JA) biosynthesis (rather than salicylic acid biosynthesis) and signal transduction were significantly activated. Strikingly, the DHL-induced systemic resistance against B. cinerea was blocked in the tomato JA biosynthesis mutant spr2 and JA signaling gene-silenced plants. Our findings highlight the role of DHL in systemic resistance against economically important necrotrophic pathogens and suggest that DHL-induced immunity against B. cinerea is largely dependent on the JA signaling pathway. Manipulation of DHL-induced resistance is an attractive disease management strategy that could potentially be used to enhance disease resistance in diverse plant species.

Topics: 4-Butyrolactone; Arabidopsis; Botrytis; Cyclopentanes; Disease Resistance; Gene Silencing; Homoserine; Oxylipins; Plant Diseases; Signal Transduction; Solanum lycopersicum

Sucrose non-fermenting-1-related protein kinase-1 (SnRK1) belongs to a family of evolutionary conserved kinases with orthologs in all eukaryotes, ranging from yeasts (SnF1) to mammals (AMP-Activated kinase). These kinases sense energy deficits caused by nutrient limitation or stress and coordinate the required adaptations to maintain energy homeostasis and survival. In plants, SnRK1 is a global regulator of plant metabolism and is also involved in abiotic stress responses. Its role in the response to biotic stress, however, is only starting to be uncovered. Here we studied the effect of altered SnRK1a expression on growth and plant defense in rice. OsSnRK1a overexpression interfered with normal growth and development and increased resistance against both (hemi)biotrophic and necrotrophic pathogens, while OsSnRK1a silencing in RNAi lines increased susceptibility. OsSnRK1a overexpression positively affected the salicylic acid pathway and boosted the jasmonate-mediated defense response after inoculation with the blast fungus Pyricularia oryzae. Together these findings strongly suggest OsSnRK1a to be involved in plant basal immunity and favor a model whereby OsSnRK1a acts as a master switch that regulates growth-immunity trade-offs.

Topics: Adaptation, Physiological; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Immunity; Plant Proteins; Plants, Genetically Modified; Protein Serine-Threonine Kinases; Salicylic Acid

The WRKY web, which is comprised of a subset of WRKY transcription factors (TFs), plays a crucial role in the regulation of plant immunity, however, the mode of organization and operation of this network remains obscure, especially in non-model plants such as pepper (

Topics: Capsicum; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Plant Proteins; Ralstonia solanacearum; Signal Transduction; Transcription Factors

Plants are constantly exposed to a variety of environmental stresses, including herbivory. How plants perceive herbivores on a molecular level is poorly understood. Leucine-rich repeat receptor-like kinases (LRR-RLKs), the largest subfamily of RLKs, are essential for plants to detect external stress signals, and may therefore also be involved in herbivore perception. Here, we employed RNA interference silencing, phytohormone profiling and complementation, as well as herbivore resistance assays, to investigate the requirement of an LRR-RLK for the initiation of rice (Oryza sativa) defenses against the chewing herbivore striped stem borer (SSB) Chilo suppressalis. We discovered a plasma membrane-localized LRR-RLK, OsLRR-RLK1, whose transcription is strongly up-regulated by SSB attack and treatment with oral secretions of Spodoptera frugiperda. OsLRR-RLK1 acts upstream of mitogen-activated protein kinase (MPK) cascades, and positively regulates defense-related MPKs and WRKY transcription factors. Moreover, OsLRR-RLK1 is a positive regulator of SSB-elicited, but not wound-elicited, levels of jasmonic acid and ethylene, trypsin protease inhibitor activity and plant resistance towards SSB. OsLRR-RLK1 therefore plays an important role in herbivory-induced defenses of rice. Given the well-documented role of LRR-RLKs in the perception of stress-related molecules, we speculate that OsLRR-RLK1 may be involved in the perception of herbivory-associated molecular patterns.

Topics: Animals; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Gene Silencing; Herbivory; Lepidoptera; Leucine-Rich Repeat Proteins; Mastication; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Proteins; Salicylic Acid; Signal Transduction; Transcription Factors

Herbivorous attack induces plant defenses. There is evidence that some pests suppress these defenses by interfering with signaling pathways. We here report that infestation by the white-backed planthopper, Sogatella furcifera, induces defense responses in rice and infection of the southern rice black-streaked dwarf virus in the planthoppers partially suppresses the planthopper-induced plant defenses. Salicylic acid (SA) levels generally showed a temporal increase pattern while jasmonic acid (JA) levels generally exhibited a decrease pattern in the planthopper-infested plants, irrespective of virus infection status in the insects. The increase in SA was less while the decrease in JA was more in the viruliferous insect-infested plants than in the nonviruliferous insect-infested plants at both 48 and 72 h post infestation. The phytohormone levels corresponded to the patterns of relative expression levels of SA-marker genes (ICS1 and NPR1) and JA-marker gene (AOS2) in the plant treatments. Planthoppers performed better on the uninfested plants than on the previously infested plants and were of not significant increase in performance on the plants previously attacked by viruliferous planthoppers in comparison with the plants previously attacked by nonviruliferous insects. Our results indicate that the virus plays a role in partially suppressing the plant defenses induced by the planthopper. These findings provide a new perspective on plant-virus-vector interactions.

Topics: Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Hemiptera; Herbivory; Host-Pathogen Interactions; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Reoviridae; Salicylic Acid

Plant growth promoting rhizobacteria have been proposed as effective biocontrol agents against several fungal and bacterial plant pathogens. However, there is limited knowledge regarding their effect against viruses. In this study, Bacillus amyloliquefaciens strain MBI600 (MBI600), active ingredient of the biological fungicide Serifel® (BASF SE), was tested for its antiviral action in tomato plants. Drench, foliar or soil amendment applications of MBI600 reduced up to 80% the incidence of Tomato spotted wilt virus under two different sets of environmental conditions. In addition, drench application of MBI600 delayed Potato virus Y systemic accumulation. Transcriptional analysis of a range of genes associated with salicylic acid (SA)- or jasmonic acid - related defense, priming or basal defense against viruses, revealed the induction of the SA signaling pathway in tomato after MBI600 treatment, and discrete gene expression patterns in plant response to TSWV and PVY infection.

Topics: Bacillus amyloliquefaciens; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Proteins; Potyvirus; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Tospovirus

Tea plant (Camellia sinensis (L) O. Kuntze) respond to herbivore attack through large changes in defense related metabolism and gene expression. Ectropis oblique (Prout) is one of the most devastating insects that feed on tea leaves and tender buds, which can cause severe production loss and deteriorate the quality of tea. To elucidate the biochemicals and molecular mechanism of defense against tea geometrid (TG), transcriptome and metabolome of TG interaction with susceptible (SG) and resistance (RG) tea genotypes were analyzed by using UPLC-Q-TOF-MS, GC-MS, and RNA-seq technologies. This revealed that jasmonic acid was highly induced in RG, following a plethora of secondary metabolites involved in defense against TG could be induced by jasmonic acid signaling pathway. However, the constitutively present of salicylic acid in SG might be a suppressor of jasmonate signaling and thus misdirect tea plants against TG. Furthermore, flavonoids and terpenoids biosynthesis pathways were highly activated in RG to constitute the chemical barrier on TG feeding behavior. In contrast, fructose and theanine, which can act as feeding stimulants were observed to highly accumulate in SG. Being present in the major hub, 39 transcription factors or protein kinases among putative candidates were identified as master regulators from protein-protein interaction network analysis. Together, the current study provides a comprehensive gene expression and metabolite profiles, which can shed new insights into the molecular mechanism of tea defense against TG. The candidate genes and specific metabolites identified in the present study can serve as a valuable resource for unraveling the possible defense mechanism of plants against various biotic stresses.

Topics: Biosynthetic Pathways; Camellia sinensis; Cyclopentanes; Disease Resistance; Flavonoids; Gas Chromatography-Mass Spectrometry; Gene Expression Profiling; Gene Expression Regulation, Neoplastic; Gene Regulatory Networks; Metabolomics; Oxylipins; Plant Proteins; Salicylic Acid; Sequence Analysis, RNA; Terpenes

Agricultural crops are exposed to a range of daylengths, which act as important environmental cues for the control of developmental processes such as flowering. To explore the additional effects of daylength on plant function, we investigated the transcriptome of Arabidopsis (

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cryptochromes; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Light; Mutation; Oxylipins; Photoperiod; Phytochrome A; Plant Diseases; Plants, Genetically Modified; Transcriptome; Ubiquitin-Protein Ligases

Nitrogen dioxide (NO

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Cytochrome P-450 Enzyme System; Disease Resistance; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Nitrogen Dioxide; Oxidants, Photochemical; Oxylipins; Plant Diseases; Plant Leaves; Pseudomonas syringae; Salicylic Acid; Time Factors

Mitogen-activated protein kinases (MAPKs) play an important role in defense responses to biotic and abiotic stresses. In order to investigate the role of SlMAPK3 in tomato plant resistance to Botrytis cinerea, two lines of slmapk3 mutants and wild-type (WT) tomato plants were used. The results showed that slmapk3 mutants were more susceptible to B. cinerea and that knockout of SlMAPK3 reduced the activities of defense enzymes and enhanced the accumulation of reactive oxygen species (ROS). Furthermore, we detected the expressions of salicylic acid (SA) and jasmonic acid (JA) signaling-related genes and found that knockout of SlMAPK3 enhanced the expressions of SlPR1, SlPAD4 and SlEDS1, whereas reduced the expressions of SlLoxC, SlPI I and SlPI II and enhanced the expressions of SlJAZ1 and SlMYC2. We postulate that SlMAPK3 plays a positive role in tomato plant resistance to B. cinerea through regulating ROS accumulation and SA and JA defense signaling pathways.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Knockout Techniques; Gene Silencing; Mitogen-Activated Protein Kinases; Oxylipins; Plant Diseases; Plant Proteins; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Solanum lycopersicum

In cultivated tomato (Solanum lycopersicum), increases in photosynthetically active radiation (PAR) induce type VI leaf glandular trichomes, which are important defensive structures against arthropod herbivores. Yet, how PAR affects the type VI trichome-associated leaf chemistry and its biological significance with respect to other photomorphogenic responses in this agronomically important plant species is unknown. We used the type VI trichome-deficient tomato mutant odorless-2 (od-2) and its wild type to investigate the influence of PAR on trichome-associated chemical defenses against thrips (Frankliniella occidentalis). High PAR increased thrips resistance in wild-type plants, but not in od-2. Furthermore, under high PAR, thrips preferred od-2 over the wild type. Both genotypes increased type VI trichome densities under high PAR. Wild-type plants, however, produced more trichome-associated allelochemicals, i.e. terpenes and phenolics, these being undetectable or barely altered in od-2. High PAR increased leaf number and thickness, and induced profound but similar metabolomic changes in wild-type and od-2 leaves. Enhanced PAR also increased levels of ABA in wild-type and od-2 plants, and of auxin in od-2, while the salicylic acid and jasmonate concentrations were unaltered. However, in both genotypes, high PAR induced the expression of jasmonic acid-responsive defense-related genes. Taken together, our results demonstrate that high PAR-mediated induction of trichome-associated chemical defenses plays a prominent role in tomato-thrips interactions.

Topics: Abscisic Acid; Animals; Cyclopentanes; Disease Resistance; Fatty Acids, Unsaturated; Gene Expression Regulation, Plant; Genotype; Indoleacetic Acids; Light; Metabolomics; Mutation; Oxylipins; Pheromones; Plant Diseases; Plant Leaves; RNA, Messenger; Salicylic Acid; Solanum lycopersicum; Thysanoptera; Trichomes; Volatile Organic Compounds

Topics: Cyclopentanes; Disease Resistance; Gossypium; Oxylipins; Peroxisomes; Phosphorylation; Plant Diseases; Plant Growth Regulators; Plant Proteins; Protein Kinases; Verticillium

Plants damaged by herbivore feeding can induce defensive responses that reduce herbivore growth. The slow-growth, high-mortality hypothesis postulates that these non-lethal plant defenses prolong the herbivore's period of susceptibility to natural enemies, such as predators and parasitoids. While many juvenile animals increase their disease resistance as they grow, direct tests of the slow-growth, high-mortality hypothesis in the context of plant-herbivore-pathogen interactions are lacking. Caterpillars increase their resistance to lethal baculoviruses as they develop within and across instars, a phenomenon termed developmental resistance. Progression of developmental resistance can occur through age-related increases in systemic immune functioning and/or midgut-based resistance. Here, we examined the slow-growth, high-mortality hypothesis in the context of developmental resistance of caterpillars to baculoviruses. Intra-stadial (within-instar) developmental resistance of the fall armyworm, Spodoptera frugiperda, to an oral inoculum of the baculovirus SfMNPV increased more rapidly with age when larvae were fed on non-induced foliage than foliage that was induced by jasmonic acid (a phytohormone that up-regulates plant anti-herbivore defenses). The degree of developmental resistance observed was attributable to larval weight at the time of virus inoculation. Thus, slower growth on induced plants prolonged the window of larval susceptibility to the baculovirus. Developmental resistance on induced and non-induced plants was absent when budded virus was injected intrahemocoelically bypassing the midgut, suggesting that developmental resistance was gut-based. Addition of fluorescent brightener, which weakens midgut-based resistance mechanisms to oral virus challenge, abolished developmental resistance. These results highlight the impact of plant defenses on herbivore growth rate and consequences for disease risk.

Topics: Animals; Cyclopentanes; Disease Resistance; Nucleopolyhedroviruses; Oxylipins; Plant Immunity; Spodoptera

The phytohormone 7-iso-(+)-jasmonoyl-L-isoleucine (JA-Ile) mediates plant defense responses against herbivore and pathogen attack, and thus increases plant resistance against foreign invaders. However, JA-Ile also causes growth inhibition; and therefore JA-Ile is not a practical chemical regulator of plant defense responses. Here, we describe the rational design and synthesis of a small molecule agonist that can upregulate defense-related gene expression and promote pathogen resistance at concentrations that do not cause growth inhibition in Arabidopsis. By stabilizing interactions between COI1 and JAZ9 and JAZ10 but no other JAZ isoforms, the agonist leads to formation of JA-Ile co-receptors that selectively activate the JAZ9-EIN3/EIL1-ORA59 signaling pathway. The design of a JA-Ile agonist with high selectivity for specific protein subtypes may help promote the development of chemical regulators that do not cause a tradeoff between growth and defense.

Topics: Arabidopsis; Arabidopsis Proteins; Computer Simulation; Cyclopentanes; Defensins; Disease Resistance; DNA-Binding Proteins; Drug Design; Isoleucine; Nuclear Proteins; Oxylipins; Peptide Termination Factors; Repressor Proteins; Stereoisomerism; Transcription Factors

The AvrRpt2

Topics: Bacterial Proteins; Cyclopentanes; Disease Resistance; Erwinia amylovora; Host-Pathogen Interactions; Malus; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Salicylic Acid; Virulence Factors

Promoters of many defense related genes are enriched with W-box elements serving as binding sites for plant specific WRKY transcription factors. In this study, expression of WRKY40 transcription factor was analyzed in two contrasting susceptible (JG62) and resistant (WR315) genotypes of chickpea infected with Foc1. The resistant plants showed up-regulation of WRKY40 under Fusarium stress, whereas in susceptible plants WRKY40 expression was absent. Additionally, global changes in the histone modification patterns were studied in above two chickpea genotypes by immunoblotting and real-time PCR analyses under control and Fusarium infected conditions. Notably, region specific Histone 3 lysine 9 acetylation, a positive marker of transcription gets enriched at WRKY40 promoter during resistant interaction with Foc1. H3K9 Ac is less enriched at WRKY40 promoter in Foc1 infected susceptible plants. WRKY40 promoter activity was induced by jasmonic acid and pathogen treatment, while salicylic acid failed to stimulate such activity. Moreover, WRKY40 was found to bind to its own promoter and auto-regulates its activity. The present study also showed that heterologous over-expression of chickpea WRKY40 triggers defense response in Arabidopsis against Pseudomonas syringae. Overall, we present epigenetic and transcriptional control of WRKY40 in chickpea under Fusarium stress and its immunomodulatory role is tested in Arabidopsis.

Topics: Arabidopsis; Cicer; Cyclopentanes; Disease Resistance; Epigenomics; Fusarium; Gene Expression; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Pseudomonas syringae; Salicylic Acid; Transcription Factors; Transgenes

Spotted-leaf mutants are important to reveal programmed cell death and defense-related pathways in rice. We previously characterized the phenotype performance of a rice spotted-leaf mutant spl21 and narrowed down the causal gene locus spl21(t) to an 87-kb region in chromosome 12 by map-based cloning.. We showed that a single base substitution from A to G at position 836 in the coding sequence of Oryza sativa beta-1,6-N-acetylglucosaminyl transferase (OsGCNT), effectively mutating Tyr to Cys at position 279 in the translated protein sequence, was responsible for the spotted-leaf phenotype as it could be rescued by functional complementation. Compared to the wild type IR64, the spotted-leaf mutant spl21 exhibited loss of chlorophyll, breakdown of chloroplasts, down-regulation of photosynthesis-related genes, and up-regulation of senescence associated genes, which indicated that OsGCNT regulates premature leaf senescence. Moreover, the enhanced resistance to the bacterial leaf blight pathogen Xanthomonas oryzae pv. oryzae, up-regulation of pathogenesis-related genes and increased level of jasmonate which suggested that OsGCNT is a negative regulator of defense response in rice. OsGCNT was expressed constitutively in the leaves, sheaths, stems, roots, and panicles, and OsGCNT-GFP was localized to the Golgi apparatus. High throughput RNA sequencing analysis provided further evidence for the biological effects of loss of OsGCNT function on cell death, premature leaf senescence and enhanced disease resistance in rice. Thus, we demonstrated that the novel OsGCNT regulated rice innate immunity and immunity-associated leaf senescence probably by changing the jasmonate metabolic pathway.. These results reveal that a novel gene Oryza sativa beta-1,6-N-acetylglucosaminyl transferase (OsGCNT) is responsible for the spotted-leaf mutant spl21, and OsGCNT acts as a negative-regulator mediating defense response and immunity-associated premature leaf senescence probably by activating jasmonate signaling pathway.

Topics: Cell Death; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; High-Throughput Nucleotide Sequencing; Host-Pathogen Interactions; Mutation; Oryza; Oxylipins; Phylogeny; Plant Diseases; Plant Immunity; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Xanthomonas

This is the first time to dissect the mechanism of NACs-mediated disease resistance in plants using metabolomic approach and discover the involvement of ABA signaling pathway in NACs-mediated disease resistance. NAC transcription factors have been validated as important regulators in stress responses, but their molecular mechanisms in plant disease resistance are still largely unknown. Here we report that the NAC gene ONAC066 (LOC_Os01g09550) is significantly activated by rice blast infection. ONAC066 is ubiquitously expressed and this protein is localized in the nucleus. Overexpression of ONAC066 quantitatively enhances resistance to blast disease and bacterial blight in rice. The transcript levels of PR genes are also dramatically induced in ONAC066 overexpressing plants. Exogenous abscisic acid (ABA) strongly activates the transcription of ONAC066 in rice. Further analysis shows that overexpression of ONAC066 remarkably suppresses the expression of ABA-related genes, whereas there are no obvious differences for salicylic acid (SA) and jasmonic acid (JA)-related genes between wild-type and ONAC066 overexpressing plants. Consistently, lower endogenous ABA levels are identified in ONAC066 overexpressing plants compared with wild-type plants before and after blast inoculation, while no significant differences are observed for the SA and JA levels. Yeast one-hybrid assays demonstrate that ONAC066 directly binds to the promoters of LIP9 and NCED4 to modulate their expression. Moreover, the metabolomic study reveals that the ONAC066 overexpressing plants accumulated higher contents of soluble sugars and amino acids both before and after pathogen attack, when compared to wild-type plants. Taken together, our results suggest that ONAC066 positively regulates rice resistance to blast and bacterial blight, and ONAC066 exerts its functions on disease resistance by modulating of ABA signaling pathway, sugars and amino acids accumulation in rice.

Topics: Abscisic Acid; Cyclopentanes; Disease Resistance; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation, Plant; Metabolomics; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Real-Time Polymerase Chain Reaction; Salicylic Acid; Signal Transduction; Transcription Factors; Two-Hybrid System Techniques

Arabidopsis AP2 FAMILY PROTEIN INVOLVED IN DISEASE DEFENSE (APD1) is a member of AP2/EREBP super-family that positively regulates SA biosynthesis and defense against virulent bacterial pathogens. Here we report additional roles of APD1 in plant defense and development. We show that APD1 function is required for light-mediated defense against bacterial pathogens and systemic acquired resistance (SAR). We demonstrate that APD1 function is not required for generating SAR mobile signal at the site of primary inoculation but is required at the distal end for SAR manifestation. In addition, the APD1 function is required for PTI-induced callose deposition, defense against necrotrophic pathogen Botrytis cinerea and Alternaria alternata, which are ethylene (ET) or ethylene-Jasmonate (JA) dependent responses. Development of seedling under dark and ET is partly dependent on APD1. The mutant apd1 plants are non-responsive towards exogenous ACC application regarding apical hook formation and hypocotyl shortening, however, possess WT-like ET-mediated root growth inhibition. JA-mediated root growth inhibition is also impaired in apd1 seedlings. Altogether our results suggest that APD1 impacts multiple aspects of plant growth and development.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Ethylenes; Multigene Family; Oxylipins; Signal Transduction; Transcription Factors

Fusarium head blight (FHB or scab) caused by Fusarium spp. is a destructive disease of wheat. Since the most effective sources of FHB resistance are typically associated with unfavorable agronomic traits, breeding commercial cultivars that combine desired agronomic traits and a high level of FHB resistance remains a considerable challenge. A better understanding of the molecular mechanisms governing FHB resistance will help to design more efficient and precise breeding strategies. Here, multiple molecular tools and assays were deployed to compare the resistant variety Sumai3 with three regionally adapted Canadian cultivars. Macroscopic and microscopic disease evaluation established the relative level of Type II FHB resistance of the four varieties and revealed that the F. graminearum infection process displayed substantial temporal differences among organs. The rachis was found to play a critical role in preventing F. graminearum spread within spikes. Large-scale, organ-specific RNA-seq at different times after F. graminearum infection demonstrated that diverse defense mechanisms were expressed faster and more intensely in the spikelet of resistant varieties. The roles of plant hormones during the interaction of wheat with F. graminearum was inferred based on the transcriptomic data obtained and the quantification of the major plant hormones. Salicylic acid and jasmonic acid were found to play predominantly positive roles in FHB resistance, whereas auxin and ABA were associated with susceptibility, and ethylene appeared to play a dual role during the interaction with F graminearum.

Topics: Abscisic Acid; Cyclopentanes; Disease Resistance; Ethylenes; Fusarium; Gene Expression Regulation, Plant; Indoleacetic Acids; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Principal Component Analysis; RNA, Plant; Salicylic Acid; Sequence Analysis, RNA; Transcriptome; Triticum

Topics: Aminohydrolases; Brassica napus; Cyclopentanes; Cytokinins; Disease Resistance; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Indoleacetic Acids; Intramolecular Transferases; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plant Roots; Plasmodiophorida

The conserved mitogen-activated protein kinase (MAPK) cascades play vital roles in plant defense responses against pathogens and insects. In the current study, the expression profiles of 17

Topics: Animals; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Hemiptera; Mitogen-Activated Protein Kinases; Oryza; Oxylipins; Plant Growth Regulators; Plant Proteins; Salicylic Acid; Signal Transduction; Virulence

Jasmonic acid (JA) plays central roles in various events in plants, especially defence against pathogens and insects. The basic helix-loop-helix (bHLH) transcription factor MYC2 has attracted attention as a master regulator of JA signalling in dicotyledonous plants. However, how MYC2 functions in monocotyledonous plants, including agriculturally important crops such as cultivated rice, has been poorly understood. To elucidate the comprehensive effects of rice MYC2 (OsMYC2) on the JA-inducible transcriptional modifications, we performed RNA-sequencing by using OsMYC2-knockdown plants (osmyc2RNAi). In osmyc2RNAi, JA-inducible expression of many defence-related genes, for example chitinases and proteinase inhibitors, was compromised. Decrease in JA-dependent activation of the biosynthetic pathways of specialised metabolites, especially defence compounds, was also evident in the osmyc2RNAi line. Furthermore, a substantial change was noted in the expression of distinct types of transcription factors, such as MYB-type factors, likely depicting the importance of OsMYC2 in not only defence responses but also other morphogenetic events. Our findings provide fundamental information to understand the overall functions of MYC2 in JA signalling in monocotyledonous plants, which might yield agricultural benefits.

Topics: Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Ontology; Gene Silencing; High-Throughput Nucleotide Sequencing; Metabolic Networks and Pathways; Molecular Sequence Annotation; Oryza; Oxylipins; Plant Growth Regulators; Plant Proteins; RNA, Small Interfering; Signal Transduction; Trans-Activators; Transcription, Genetic

Eucalyptus species are cultivated for forestry and are of economic importance. The fungal stem canker pathogen Chrysoporthe austroafricana causes disease of varying severity on E. grandis. The Eucalyptus grandis-Chrysoporthe austroafricana interaction has been established as a model system for studying Eucalyptus antifungal defence. Previous studies revealed that the phytohormone salicylic acid (SA) affects the levels of resistance in highly susceptible (ZG14) and moderately resistant (TAG5) clones. The aims of this study were to examine histochemical changes in response to wounding and inoculation as well as host responses at the protein level. The anatomy and histochemical changes induced by wounding and inoculation were similar between the clones, suggesting that anatomical differences do not underlie their different levels of resistance. Tyloses and gum-like substances were present after inoculation and wounding, but cell death occurred only after inoculation. Hyphae of C. austroafricana were observed inside dead and living cells, suggesting that the possibility of a hemibiotrophic interaction requires further investigation. Proteomics analysis revealed the possible involvement of proteins associated with cell death, SA signalling and systemic resistance. In combination with previous information, this study forms a basis for future functional characterisation of candidate genes involved in resistance of E. grandis to C. austroafricana.

Topics: Ascomycota; Cyclopentanes; Disease Resistance; Eucalyptus; Gene Expression Profiling; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Stems; Salicylic Acid; Xylem

The indirect interactions between insect vectors, such as whiteflies, and the viruses they transmit, such as begomoviruses, via host plants may produce a range of outcome depending on the species/strain of each of the three organisms involved, and the mechanisms underlying the variations are not well understood. Here, we observed the performance of whiteflies on three types of tomato, which vary in level of jasmonic acid (JA)-related resistance and were either uninfected or infected by a begomovirus, to investigate the role of JA-related resistance in mediating whitefly-begomovirus interactions. Compared to the performance of whiteflies on plants of the wild type, the performance was elevated on plants deficient in JA-related resistance but reduced on plants with a high level of JA-related resistance. Further, on plants with a high level of JA-related resistance, the whitefly performed better on virus-infected than on uninfected plants; however, on tomato plants deficient in JA-related resistance, whitefly performance was less affected by the virus-infection of plants. Additionally, the expression of the JA-regulated defense gene PI-II in tomato plants was repressed by virus infection. These findings suggest that JA-related resistance plays an important role in the tripartite interactions between whitefly, begomovirus and tomato plant.

Topics: Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Hemiptera; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plants, Genetically Modified; Signal Transduction; Solanum lycopersicum

The hemibiotrophic fungus Colletotrichum graminicola may cause severe damage to maize, affecting normal development of the plant and decreasing grain yield. In this context, understanding plant defense pathways at the inoculation site and systemically in uninoculated tissues can help in the development of genetic engineering of resistance against this pathogen. Previous work has discussed the molecular basis of maize - C. graminicola interaction. However, many genes involved in defense have not yet been exploited for lack of annotation in public databases. Here, changes in global gene expression were studied in root, male and female inflorescences of maize under local and systemic fungal infection treatments, respectively. RNA-Seq with qPCR was used to indicate genes involved in plant defense. We found that systemic acquired resistance induction in female inflorescences mainly involves accumulation of salicylic acid (SA)-inducible defense genes (ZmNAC, ZmHSF, ZmWRKY, ZmbZIP and PR1) and potential genes involved in chromatin modification. Furthermore, transcripts involved in jasmonic acid (JA) and ethylene (ET) signaling pathways were also accumulated and may participate in plant immunity. Moreover, several genes were functionally re-annotated based on domain signature, indicating novel candidates to be tested in strategies involving gene knockout and overexpression in plants.

Topics: Colletotrichum; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Salicylic Acid; Transcriptome; Zea mays

Sound vibration (SV), a mechanical stimulus, can trigger various molecular and physiological changes in plants like gene expression, hormonal modulation, induced antioxidant activity and calcium spiking. It also alters the seed germination and growth of plants. In this study, we investigated the effects of SV on the resistance of Arabidopsis thaliana against Botrytis cinerea infection. The microarray analysis was performed on infected Arabidopsis plants pre-exposed to SV of 1000 Hertz with 100 decibels. Broadly, the transcriptomic analysis revealed up-regulation of several defense and SA-responsive and/or signaling genes. Quantitative real-time PCR (qRT-PCR) analysis of selected genes also validated the induction of SA-mediated response in the infected Arabidopsis plants pre-exposed to SV. Corroboratively, hormonal analysis identified the increased concentration of salicylic acid (SA) in the SV-treated plants after pathogen inoculation. In contrast, jasmonic acid (JA) level in the SV-treated plants remained stable but lower than control plants during the infection. Based on these findings, we propose that SV treatment invigorates the plant defense system by regulating the SA-mediated priming effect, consequently promoting the SV-induced resistance in Arabidopsis against B. cinerea.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Salicylic Acid; Sound; Vibration

Metabolomic and transcriptomic approaches were used to dissect the enhanced disease resistance in the plants harbouring a RNA interfering construct of OsWRKY62 and OsWRKY76 (dsOW62/76) genes. The primary metabolic pathways were activated in dsOW62/76 compared with wild-type (ZH17) plants, revealed by increased accumulation of amino acids and constituents of citric acid cycle etc. Contents of phenolic acids derived from phenylpropanoid pathway were elevated in dsOW62/76 plants. Importantly, phenolamides, conjugates of the phenolic acids with amines, were detected in large number and mostly at higher levels in dsOW62/76 compared with ZH17 plants; however, the free pools of flavonoids were mostly decreased in dsOW62/76. Salicylic acid (SA) and jasmonic acid (JA)/JA-Ile contents were increased in dsOW62/76 and knockout lines of individual OsWRKY62 and OsWRKY76 genes. Transcription of isochorismate synthase (OsICS1) gene was suppressed in dsOW62/76 and in MeJA-treated rice plants, whereas the transcription level of cinnamoyl-CoA hydratase-dehydrogenase (OsCHD) gene for β-oxidation in peroxisome was increased. The calli with OsCHD mutation showed markedly decreased SA accumulation. These results indicate that OsWRKY62 and OsWRKY76 function as negative regulators of biosynthetic defense-related metabolites and provide evidence for an important role of phenylpropanoid pathway in SA production in rice.

Topics: Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Magnaporthe; Metabolic Networks and Pathways; Oryza; Oxylipins; Plant Diseases; Plants, Genetically Modified; Salicylic Acid; Transcription Factors; Transcription, Genetic; Xanthomonas

Plants actively perceive and respond to perturbations in their cell walls which arise during growth, biotic and abiotic stresses. However, few components involved in plant cell wall integrity sensing have been described to date. Using a reverse-genetic approach, we identified the Arabidopsis thaliana leucine-rich repeat receptor kinase MIK2 as an important regulator of cell wall damage responses triggered upon cellulose biosynthesis inhibition. Indeed, loss-of-function mik2 alleles are strongly affected in immune marker gene expression, jasmonic acid production and lignin deposition. MIK2 has both overlapping and distinct functions with THE1, a malectin-like receptor kinase previously proposed as cell wall integrity sensor. In addition, mik2 mutant plants exhibit enhanced leftward root skewing when grown on vertical plates. Notably, natural variation in MIK2 (also named LRR-KISS) has been correlated recently to mild salt stress tolerance, which we could confirm using our insertional alleles. Strikingly, both the increased root skewing and salt stress sensitivity phenotypes observed in the mik2 mutant are dependent on THE1. Finally, we found that MIK2 is required for resistance to the fungal root pathogen Fusarium oxysporum. Together, our data identify MIK2 as a novel component in cell wall integrity sensing and suggest that MIK2 is a nexus linking cell wall integrity sensing to growth and environmental cues.

Topics: Arabidopsis; Arabidopsis Proteins; Cell Wall; Cellulose; Cyclopentanes; Disease Resistance; Fusarium; Gene Expression Regulation, Plant; Lignin; Oxylipins; Plant Diseases; Plant Roots; Protein Kinases; Receptors, Cell Surface; Sodium Chloride; Stress, Physiological

The plant hormone jasmonate (JA) promotes the degradation of JASMONATE ZIM-DOMAIN (JAZ) proteins to relieve repression on diverse transcription factors (TFs) that execute JA responses. However, little is known about how combinatorial complexity among JAZ-TF interactions maintains control over myriad aspects of growth, development, reproduction, and immunity. We used loss-of-function mutations to define epistatic interactions within the core JA signaling pathway and to investigate the contribution of MYC TFs to JA responses in Arabidopsis thaliana. Constitutive JA signaling in a jaz quintuple mutant (jazQ) was largely eliminated by mutations that block JA synthesis or perception. Comparison of jazQ and a jazQ myc2 myc3 myc4 octuple mutant validated known functions of MYC2/3/4 in root growth, chlorophyll degradation, and susceptibility to the pathogen Pseudomonas syringae. We found that MYC TFs also control both the enhanced resistance of jazQ leaves to insect herbivory and restricted leaf growth of jazQ. Epistatic transcriptional profiles mirrored these phenotypes and further showed that triterpenoid biosynthetic and glucosinolate catabolic genes are up-regulated in jazQ independently of MYC TFs. Our study highlights the utility of genetic epistasis to unravel the complexities of JAZ-TF interactions and demonstrates that MYC TFs exert master control over a JAZ-repressible transcriptional hierarchy that governs growth-defense balance.

Topics: Anthocyanins; Arabidopsis; Arabidopsis Proteins; Chlorophyll; Cyclopentanes; Disease Resistance; Epistasis, Genetic; Flowers; Gene Expression Regulation, Plant; Mutation; Oxylipins; Plant Leaves; Plant Roots; RNA, Messenger; Signal Transduction; Transcription Factors; Transcription, Genetic

Root colonization by Trichoderma fungi can trigger induced systemic resistance (ISR). In Arabidopsis, Trichoderma-ISR relies on the transcription factor MYB72, which plays a dual role in the onset of ISR and the activation of Fe uptake responses. Volatile compounds (VCs) from rhizobacteria are important elicitors of MYB72 in Arabidopsis roots. Here, we investigated the mode of action of VCs from Trichoderma fungi in the onset of ISR and Fe uptake responses. VCs from Trichoderma asperellum and Trichoderma harzianum were applied in an in vitro split-plate system with Arabidopsis or tomato seedlings. Locally, Trichoderma-VCs triggered MYB72 expression and molecular, physiological and morphological Fe uptake mechanisms in Arabidopsis roots. In leaves, Trichoderma-VCs primed jasmonic acid-dependent defences, leading to an enhanced resistance against Botrytis cinerea. By using Arabidopsis micrografts of VCs-exposed rootstocks and non-exposed scions, we demonstrated that perception of Trichoderma-VCs by the roots leads to a systemic signal that primes shoots for enhanced defences. Trichoderma-VCs also elicited Fe deficiency responses and shoot immunity in tomato, suggesting that this phenomenon is expressed in different plant species. Our results indicate that Trichoderma-VCs trigger locally a readjustment of Fe homeostasis in roots, which links to systemic elicitation of ISR by priming of jasmonic acid-dependent defences.

Topics: Air; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Iron; Oxylipins; Plant Diseases; Plant Leaves; Plant Roots; Plant Shoots; Signal Transduction; Solanum lycopersicum; Trichoderma; Volatile Organic Compounds

The hormone jasmonate (JA), which functions in plant immunity, regulates resistance to pathogen infection and insect attack through triggering genome-wide transcriptional reprogramming in plants. We show that the basic helix-loop-helix transcription factor (TF) MYC2 in tomato (

Topics: Amino Acid Motifs; Binding Sites; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Ontology; Genes, Plant; Models, Biological; Oxylipins; Plant Diseases; Plant Immunity; Plant Proteins; Promoter Regions, Genetic; Protein Binding; Sequence Analysis, RNA; Solanum lycopersicum; Transcription, Genetic; Transcriptome

Jasmonates (JAs) orchestrate immune responses upon wound/herbivore injury or infection by necrotrophic pathogens. Elucidation of catabolic routes has revealed new complexity in jasmonate metabolism. Two integrated pathways attenuate signaling by turning over the active hormone jasmonoyl-isoleucine (JA-Ile) through ω-oxidation or deconjugation, and define an indirect route forming the derivative 12OH-JA. Here, we provide evidence for a second 12OH-JA formation pathway by direct jasmonic acid (JA) oxidation. Three jasmonic acid oxidases (JAOs) of the 2-oxoglutarate dioxygenase family catalyze specific oxidation of JA to 12OH-JA, and their genes are induced by wounding or infection by the fungus Botrytis cinerea. JAO2 exhibits the highest basal expression, and its deficiency in jao2 mutants strongly enhanced antifungal resistance. The resistance phenotype resulted from constitutive expression of antimicrobial markers rather than from their higher induction in infected jao2 plants and could be reversed by ectopic expression of any of the three JAOs in jao2. Elevated defense in jao2 was dependent on the activity of JASMONATE RESPONSE 1 (JAR1) and CORONATINE-INSENSITIVE 1 (COI1) but was not correlated with enhanced JA-Ile accumulation. Instead, jao2 mutant lines displayed altered accumulation of several JA species in healthy and challenged plants, suggesting elevated metabolic flux through JA-Ile. Collectively, these data identify the missing enzymes hydroxylating JA and uncover an important metabolic diversion mechanism for repressing basal JA defense responses.

Topics: Antifungal Agents; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Dioxygenases; Disease Resistance; Gene Knockout Techniques; Hydroxylation; Isoleucine; Oxylipins; Plant Diseases; Plant Leaves; Signal Transduction; Up-Regulation

A chemical screen of plant-derived compounds identified holaphyllamine, a steroid, able to trigger defense responses in Arabidopsis thaliana and improve resistance against the pathogenic bacterium Pseudomonas syringae pv tomato DC3000. A chemical screen of 1600 plant-derived compounds was conducted and allowed the identification of a steroid able to activate defense responses in A. thaliana at a concentration of 1 µM without altering growth. The identified compound is holaphyllamine (HPA) whose chemical structure is similar to steroid pregnanes of mammals. Our data show that HPA, which is not constitutively present in A. thaliana, is able to trigger the formation of reactive oxygen species, deposition of callose and expression of several pathogenesis-related genes of the salicylic and jasmonic acid pathways. In addition, the results show that pre-treatment of A. thaliana seedlings with HPA before infection with the pathogenic bacterium Pseudomonas syringae pv tomato DC3000 results in a significant reduction of symptoms (i.e., reduction of bacterial colonies). Using A. thaliana mutants, we have found that the activation of defense responses by HPA does not depend on BRI1/BAK1 receptor kinases. Finally, a structure/function study reveals that the minimal structure required for activity is a 5-pregnen-20-one steroid with an equatorial nucleophilic group in C-3. Together, these findings demonstrate that HPA can activate defense responses that lead to improved resistance against bacterial infection in A. thaliana.

Topics: Arabidopsis; Arabidopsis Proteins; Cells, Cultured; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Mutation; Nicotiana; Oxylipins; Phytosterols; Plant Diseases; Plant Growth Regulators; Plant Leaves; Pseudomonas syringae; Reactive Oxygen Species; Respiratory Burst; Salicylic Acid; Seedlings; Small Molecule Libraries

A key member of the Pm21 resistance gene locus, Stpk-V, derived from Haynaldia villosa, was shown to confer broad-spectrum resistance to wheat powdery mildew. The present study was planned to investigate the resistance mechanism mediated by Stpk-V. Transcriptome analysis was performed in Stpk-V transgenic plants and recipient Yangmai158 upon Bgt infection, and detailed histochemical observations were conducted. Chromosome location of Stpk-V orthologous genes in Triticeae species was conducted for evolutionary study and over-expression of Stpk-V both in barley and Arabidopsis was performed for functional study. The transcriptome results indicate, at the early infection stage, the ROS pathway, JA pathway and some PR proteins associated with the SA pathway were activated in both the resistant Stpk-V transgenic plants and susceptible Yangmai158. However, at the later infection stage, the genes up-regulated at the early stage were continuously held only in the transgenic plants, and a large number of new genes were also activated in the transgenic plants but not in Yangmai158. Results indicate that sustained activation of the early response genes combined with later-activated genes mediated by Stpk-V is critical for resistance in Stpk-V transgenic plants. Stpk-V orthologous genes in the representative grass species are all located on homologous group six chromosomes, indicating that Stpk-V is an ancient gene in the grasses. Over-expression of Stpk-V enhanced host resistance to powdery mildew in barley but not in Arabidopsis. Our results enable a better understanding of the resistance mechanism mediated by Stpk-V, and establish a solid foundation for its use in cereal breeding as a gene resource.

Topics: Arabidopsis; Ascomycota; Cyclopentanes; Disease Resistance; Ethylenes; Genes, Plant; Metabolic Networks and Pathways; Oxylipins; Plant Diseases; Plants, Genetically Modified; Reactive Oxygen Species; Real-Time Polymerase Chain Reaction; Salicylic Acid; Triticum

Fusarium poae has been considered as a minor species among those that cause the FHB disease but in recent years several researchers have documented a high frequency of occurrence in several crops. We evaluated the ability of F. poae to produce symptoms in A. thaliana leaves. Moreover, we analyzed the defense of A. thaliana against F. poae using SA, JA, and ET mutants and we monitored the expression level of genes involved in the main signaling pathways related to plant defense. Symptoms were observed in the inoculated leaves demonstrating the ability of F. poae to infect A. thaliana leaves. Moreover, the npr1-1 mutants presented low symptoms compared to Col-0, etr2-1, and coi1-1 and that the coi1-1 mutant was the most susceptible genotypes followed by etr2-1 genotypes. The RT-PCR revealed that PDF1.2, CHI/PR3, and ERF1, three important JA-ET responsive genes and NPR1 and PR1, which are regulated by SA signaling, were expressed upon F. poae inoculation. Our results suggest that JA and ET could play a key role in Arabidopsis leaves defense against F. poae representing the first evaluation of the response of the main A. thaliana phytohormones involved in plant defense in the presence of F. poae.

Topics: Arabidopsis; Cyclopentanes; Disease Resistance; DNA, Fungal; Ethylenes; Fusarium; Gene Expression Regulation, Fungal; Gene Expression Regulation, Plant; Genotype; Mutation; Oxylipins; Plant Leaves; RNA, Fungal; Signal Transduction

Jasmonates (JAs), lipid-derived phytohormones, regulate plant growth, development and defenses against biotic stresses. CORONATINE INSENSITIVE1 perceives bioactive JA and recruits JASMONATE ZIM-DOMAIN (JAZ) proteins for ubiquitination and subsequent degradation via the 26S proteasome, which de-represses JAZ-targeted transcription factors that regulate diverse JA responses. Recent studies showed that the Arabidopsis basic helix-loop-helix transcription factor MYC5 interacts with JAZs and regulates stamen development. However, whether MYC5 mediates other JA responses is unclear. Here, we show that MYC5 functions redundantly with MYC2, MYC3 and MYC4 to modulate JA-regulated root growth inhibition and plant defenses against insect attack and pathogen infection, and that it positively regulates JA-induced leaf senescence. Our findings define MYC5 as an important regulator that is essential for diverse JA responses.

Topics: Animals; Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Transcription Factors; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Herbivory; Oxylipins; Plant Diseases; Plant Leaves; Plant Roots; Plants, Genetically Modified; Spodoptera

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Regulatory Networks; Genotype; Host-Pathogen Interactions; Indoles; Mutation; Oxylipins; Plant Diseases; Salicylic Acid; Signal Transduction; Thiazoles; Transcriptome

The productivity of Oilseed Brassica, one of the economically important crops of India, is seriously affected by the disease, Alternaria blight. The disease is mainly caused by two major necrotrophic fungi, Alternaria brassicae and Alternaria brassicicola which are responsible for significant yield losses. Till date, no resistant source is available against Alternaria blight, hence plant breeding methods can not be used to develop disease resistant varieties. Jasmonate mediated signalling pathway, which is known to play crucial role during defense response against necrotrophs, could be strengthened in Brassica plants to combat the disease. Since scanty information is available in Brassica-Alternaria pathosystems at molecular level therefore, in the present study efforts have been made to model jasmonic acid pathway in Arabidopsis thaliana to simulate the dynamic behaviour of molecular species in the model. Besides, the developed model was also analyzed topologically for investigation of the hubs node. COI1 is identified as one of the promising candidate genes in response to Alternaria and other linked components of plant defense mechanisms against the pathogens. The findings from present study are therefore informative for understanding the molecular basis of pathophysiology and rational management of Alternaria blight for securing food and nutritional security.

Topics: Alternaria; Arabidopsis; Arabidopsis Proteins; Biosynthetic Pathways; Brassica; Computational Biology; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Regulatory Networks; Models, Biological; Oxylipins; Signal Transduction

Arabidopsis MYC2 (AtMYC2) is a bHLH class transcription factor that mediates light-dependent seedling development, disease defence, JA and ABA signalling. AtMYC2 gene modulates hypocotyl elongation and expression of chlorophyll A/B binding protein 1 (CAB1) and rubisco small subunit protein1 (RBCS1) under blue light. The atmyc2 mutants are resistant against virulent bacterial pathogens. MYC2 orthologues from several crop plants have been characterized. The rice gene Os10g42430 has been referred earlier as OsMYC2 and has been shown to promote expression of JA-inducible genes. However, the role of OsMYC2 in seedling development under ABA, dark or light of specific wavelengths was not known. It was also not known whether OsMYC2 complements AtMYC2 function in Arabidopsis. We show here that expression of OsMYC2 in the atmyc2 mutant of Arabidopsis complements the blue-light-mediated defects in hypocotyl elongation and expression of CAB1 and RBCS1. We generated multiple transgenic rice lines for over-expression and RNAi-mediated suppression of OsMYC2. In agreement with AtMYC2 function, OsMYC2 over-expression and RNAi lines showed enhanced and suppressed seedling growth compared to WT plants respectively under blue light, and showed little effect under white light or dark. In agreement with the negative regulatory role of AtMYC2 in disease defence, the RNAi lines showed enhanced resistance against bacterial pathogen Xanthomonas oryzae pv oryzae. However, in contrast to AtMYC2 function, OsMYC2 influences seedling development under red light and show no effect in ABA-mediated seed germination. Thus, the results suggest evolutionarily conserved as well as the distinct role of OsMYC2 in comparison with AtMYC2.

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genetic Complementation Test; Germination; Hypocotyl; Light; Light-Harvesting Protein Complexes; Oryza; Oxylipins; Photosystem II Protein Complex; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Ribulose-Bisphosphate Carboxylase; RNA, Small Interfering; Seedlings; Seeds; Xanthomonas

The phytohormone jasmonic acid (JA) and its derivatives, collectively referred to as jasmonates, regulate many developmental processes, but are also involved in the response to numerous abiotic/biotic stresses. Thus far, powerful reverse genetic strategies employing perception, signalling or biosynthesis mutants have broadly contributed to our understanding of the role of JA in the plant stress response and development, as has the chemical gain-of-function approach based on exogenous application of the hormone. However, there is currently no method that allows for tightly controlled JA production in planta. By investigating the control of the JA synthesis pathway in bacteria-infected cotton (Gossypium hirsutum L.) plants, we identified a transcription factor (TF), named GhERF-IIb3, which acts as a positive regulator of the JA pathway. Expression of this well-conserved TF in cotton leaves was sufficient to produce in situ JA accumulation at physiological concentrations associated with an enhanced cotton defence response to bacterial infection.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Transcription Factors

On microbial attack, plants can detect invaders and activate plant innate immunity. For the detection of pathogen molecules or cell wall damage, plants employ receptors that trigger the activation of defence responses. Cell surface proteins that belong to large families of lectin receptor kinases are candidates to function as immune receptors. Here, the function of LecRK-I.9 (At5g60300), a legume-type lectin receptor kinase involved in cell wall-plasma membrane contacts and in extracellular ATP (eATP) perception, was studied through biochemical, gene expression and reverse genetics approaches. In Arabidopsis thaliana, LecRK-I.9 expression is rapidly, highly and locally induced on inoculation with avirulent strains of Pseudomonas syringae pv. tomato (Pst). Two allelic lecrk-I.9 knock-out mutants showed decreased resistance to Pst. Conversely, over-expression of LecRK-I.9 led to increased resistance to Pst. The analysis of defence gene expression suggests an alteration of both the salicylic acid (SA) and jasmonic acid (JA) signalling pathways. In particular, LecRK-I.9 expression during plant-pathogen interaction was dependent on COI1 (CORONATINE INSENSITIVE 1) and JAR1 (JASMONATE RESISTANT 1) components, and JA-responsive transcription factors (TFs) showed altered levels of expression in plants over-expressing LecRK-I.9. A similar misregulation of these TFs was obtained by JA treatment. This study identified LecRK-I.9 as necessary for full resistance to Pst and demonstrated its involvement in the control of defence against pathogens through a regulation of JA signalling components. The role of LecRK-I.9 is discussed with regard to the potential molecular mechanisms linking JA signalling to cell wall damage and/or eATP perception.

Topics: Arabidopsis; Arabidopsis Proteins; Biosynthetic Pathways; Cell Death; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucuronidase; Oxylipins; Phenotype; Plant Diseases; Plants, Genetically Modified; Protein Kinases; Pseudomonas syringae; Signal Transduction; Virulence

Under conditions that involve a high risk of competition for light among neighbouring plants, shade-intolerant species often display increased shoot elongation and greater susceptibility to pathogens and herbivores. The functional links between morphological and defence responses to crowding are not well understood. In Arabidopsis, the protein JAZ10 is thought to play a key role connecting the inactivation of the photoreceptor phytochrome B (phyB), which takes place under competition for light, with the repression of jasmonate-mediated plant defences. Here, we show that a null mutation of the JAZ10 gene in Arabidopsis did not affect plant growth nor did it suppress the shade-avoidance responses elicited by phyB inactivation. However, the jaz10 mutation restored many of the defence traits that are missing in the phyB mutant, including the ability to express robust responses to jasmonate and to accumulate indolic glucosinolates. Furthermore, the jaz10phyB double mutant showed a significantly increased resistance to the pathogenic fungus Botrytis cinerea compared with the phyB parental line. Our results demonstrate that, by inactivating JAZ10, it is possible to partially uncouple shade avoidance from defence suppression in Arabidopsis. These findings may provide clues to improve plant resistance to pathogens in crops that are planted at high density.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Glucosinolates; Light; Mutation; Nuclear Proteins; Oxylipins; Phytochrome B; Plant Diseases; Plant Immunity; Up-Regulation

Grapevine downy mildew is an important disease affecting crop production leading to severe yield losses. This study aims to identify the grapevine cultivar-specific adjustments of leaf proteome that allow the discrimination between resistance and susceptibility towards P. viticola (constitutive (0h) and in after inoculation (6, 12 and 24h). Leaf proteome analysis was performed using 2D difference gel electrophoresis followed by protein identification via mass spectrometry. In addition, we analysed ROS production, antioxidant capacity, lipid peroxidation and gene expression. Proteins related to photosynthesis and metabolism allowed the discrimination of resistant and susceptible grapevine cultivars prior to P. viticola inoculation. Following inoculation increase of hydrogen peroxide levels, cellular redox regulation, establishment of ROS signalling and plant cell death seem to be key points differentiating the resistant genotype. Lipid associated signalling events, particularly related to jasmonates appear also to play a major role in the establishment of resistance. The findings from this study contribute to a better understanding of genotype-specific differences that account for a successful establishment of a defence response to the downy mildew pathogen.. Here, we present for the first time grapevine cultivar-specific adjustments of leaf proteome that allow the discrimination between resistance and susceptibility towards P. viticola (constitutive (0h) and in after inoculation (6, 12 and 24h). We have highlighted that, following inoculation, the major factors differentiating the resistant from the susceptible grapevine cultivars are the establishment of effective ROS signalling together with lipid-associated signalling events, particularly related to jasmonates. It is believed that plants infected with biotrophic pathogens suppress JA-mediated responses, however recent evidences shown that jasmonic acid signalling pathway in grapevine resistance against Plasmopara viticola. Our results corroborate those evidences and highlight the importance of lipid- signalling for an effective resistance response against the downy mildew pathogen.

Topics: Cyclopentanes; Disease Resistance; Electrophoresis, Gel, Two-Dimensional; Gene Expression Regulation, Plant; Genotype; Lipid Metabolism; Oxidation-Reduction; Oxylipins; Peronospora; Plant Diseases; Plant Leaves; Proteome; Signal Transduction; Vitis

Rice ratooning is practiced in many rice-growing countries for achieving increased rice production with limited labour input. Here, we report that attack by insect herbivores, or treatment with a defense signaling compound in parent plants, can prime anti-herbivore defense responses in subsequent ratoon plants. We compared the defense responses of rice ratoons generated from parent plants that had been either infested by Cnaphalocrocis medinalis (rice leaffolder, LF) caterpillars or treated with methyl jasmonate (MeJA) during vegetative growth, with ratoons generated from control parent plants. Ratoon plants generated from parents receiving prior LF infestation or MeJA treatment exhibited higher jasmonic acid (JA) levels, as well as elevated levels of transcripts of defense-related genes associated with JA signaling. In addition, elevated activities of peroxidase, polyphenol oxidase and trypsin protease inhibitor were observed, as well as enhanced resistance towards subsequent LF infestation. Pre-priming of ratoon defense responses was significantly reduced in plants where expression of OsAOS (allene oxide synthase, involved in JA biosynthesis) or OsCOI1 (CORONATINE INSENSITIVE1, involved in JA perception) was inhibited by RNA interference. Our results indicate that herbivore exposure or MeJA treatment in rice parent plants enhances anti-herbivore resistance in subsequently generated ratoons through priming of JA-mediated defenses.

Topics: Acetates; Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Herbivory; Larva; Lepidoptera; Oryza; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Protease Inhibitors; RNA, Messenger; Transcription, Genetic

Plants have the ability to resist pathogen attack after infection or treatment with biotic and abiotic elicitors. In oilseed rape plant Brassica napus AACC and in the artificially synthesized Raphanus alboglabra RRCC, the root-colonizing Trichoderma harzianum TH12 fungus triggers induced systemic resistance (ISR), and its culture filtrate (CF) triggers a systemic acquired resistance (SAR) response against infection by the Sclerotinia sclerotiorum. Salicylic acid (SA) and jasmonic acid/ethylene (JA/ET) are plant hormone signals that play important roles in the regulation of ISR and SAR. In this study, at six different time points (1, 2, 4, 6, 8 and 10 days post-infection [dpi]), six resistance genes were used as markers of signaling pathways: JA/ET signaling used AOC3, PDF1.2 and ERF2 genes, while PR-1, TGA5 and TGA6 genes were used as markers of SA signaling. The results of quantitative real-time polymerase chain reaction (qRT-PCR) showed that AOC3, PDF1.2 and ERF2 expression levels in infected leaves of AACC and RRCC increase at 1 and 2 dpi with S. sclerotiorum or inoculation with TH12. PR-1, TGA5 and TGA6 expression levels increased at 8 and 10 dpi in infected leaves. PR-1, TGA5 and TGA6 expression levels increased early in plants treated with CF in both of the healthy genotypes. Furthermore, induction of SA- and JA/ET-dependent defense decreased disease symptoms in infected leaves at different times. The results suggest that the RRCC genotype exhibits resistance to disease and that the ability of TH12 and its CF to induce systemic resistance in susceptible and resistant oilseed rape genotypes exists. In addition, the results indicate for the first time that in RRCC the SA signaling pathway is involved in resistance to necrotrophic pathogens.

Topics: Ascomycota; Brassica napus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Genotype; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plant Roots; Real-Time Polymerase Chain Reaction; Salicylic Acid; Signal Transduction; Trichoderma

Potential of MoSM1, encoding for a cerato-platanin protein from Magnaporthe oryzae, in improvement of rice disease resistance was examined. Transient expression of MoSM1 in rice leaves initiated hypersensitive response and upregulated expression of defense genes. When transiently expressed in tobacco leaves, MoSM1 targeted to plasma membrane. The MoSM1-overexpressing (MoSM1-OE) transgenic rice lines showed an improved resistance, as revealed by the reduced disease severity and decreased in planta pathogen growth, against 2 strains belonging to two different races of M. oryzae, causing blast disease, and against 2 strains of Xanthomonas oryzae pv. oryzae, causing bacterial leaf blight disease. However, no alteration in resistance to sheath blight disease was observed in MoSM1-OE lines. The MoSM1-OE plants contained elevated levels of salicylic acid (SA) and jasmonic acid (JA) and constitutively activated the expression of SA and JA signaling-related regulatory and defense genes. Furthermore, the MoSM1-OE plants had no effect on drought and salt stress tolerance and on grain yield. We conclude that MoSM1 confers a broad-spectrum resistance against different pathogens through modulating SA- and JA-mediated signaling pathways without any penalty on abiotic stress tolerance and grain yield, providing a promising potential for application of MoSM1 in improvement of disease resistance in crops.

Topics: Cyclopentanes; Disease Resistance; Fungal Proteins; Gene Expression Regulation, Plant; Magnaporthe; Nicotiana; Oryza; Oxylipins; Plant Diseases; Plant Leaves; Plants, Genetically Modified; Salicylic Acid

Paraburkholderia phytofirmans PsJN is a plant growth-promoting rhizobacterium (PGPR) that stimulates plant growth and improves tolerance to abiotic stresses. This study analyzed whether strain PsJN can reduce plant disease severity and proliferation of the virulent strain Pseudomonas syringae pv. tomato DC3000, in Arabidopsis plants, through the activation of induced resistance. Arabidopsis plants previously exposed to strain PsJN showed a reduction in disease severity and pathogen proliferation in leaves compared with noninoculated, infected plants. The plant defense-related genes WRKY54, PR1, ERF1, and PDF1.2 demonstrated increased and more rapid expression in strain PsJN-treated plants compared with noninoculated, infected plants. Transcriptional analyses and functional analysis using signaling mutant plants suggested that resistance to infection by DC3000 in plants treated with strain PsJN involves salicylic acid-, jasmonate-, and ethylene-signaling pathways to activate defense genes. Additionally, activation occurs through a specific PGPR-host recognition, being a necessary metabolically active state of the bacterium to trigger the resistance in Arabidopsis, with a strain PsJN-associated molecular pattern only partially involved in the resistance response. This study provides the first report on the mechanism used by the PGPR P. phytofirmans PsJN to protect A. thaliana against a widespread virulent pathogenic bacterium.

Topics: Arabidopsis; Biofilms; Burkholderia; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Host-Pathogen Interactions; Mutation; Oxylipins; Plant Diseases; Pseudomonas syringae; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Transcription, Genetic; Virulence

Several recent studies have reported on the role of mitogen-activated protein kinase (MAPK3) in plant immune responses. However, little is known about how MAPK3 functions in tomato (Solanum lycopersicum L.) infected with tomato yellow leaf curl virus (TYLCV). There is also uncertainty about the connection between plant MAPK3 and the salicylic acid (SA) and jasmonic acid (JA) defense-signaling pathways. The results of this study indicated that SlMAPK3 participates in the antiviral response against TYLCV. Tomato seedlings were inoculated with TYLCV to investigate the possible roles of SlMAPK1, SlMAPK2, and SlMAPK3 against this virus. Inoculation with TYLCV strongly induced the expression and the activity of all three genes. Silencing of SlMAPK1, SlMAPK2, and SlMAPK3 reduced tolerance to TYLCV, increased leaf H2O2 concentrations, and attenuated expression of defense-related genes after TYLCV infection, especially in SlMAPK3-silenced plants. Exogenous SA and methyl jasmonic acid (MeJA) both significantly induced SlMAPK3 expression in tomato leaves. Over-expression of SlMAPK3 increased the transcript levels of SA/JA-mediated defense-related genes (PR1, PR1b/SlLapA, SlPI-I, and SlPI-II) and enhanced tolerance to TYLCV. After TYLCV inoculation, the leaves of SlMAPK3 over-expressed plants compared with wild type plants showed less H2O2 accumulation and greater superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) activity. Overall, the results suggested that SlMAPK3 participates in the antiviral response of tomato to TYLCV, and that this process may be through either the SA or JA defense-signaling pathways.

Topics: Begomovirus; Cyclopentanes; Disease Resistance; Enzyme Induction; Gene Expression Regulation, Plant; Gene Silencing; MAP Kinase Signaling System; Mitogen-Activated Protein Kinase 3; Oxidative Stress; Oxidoreductases; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Transcription, Genetic

Plants have developed diverse mechanisms to fine tune defence responses to different types of enemy. Cross-regulation between signalling pathways may allow the prioritization of one response over another. Previously, we identified SUPPRESSOR OF rps4-RLD1 (SRFR1) as a negative regulator of ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1)-dependent effector-triggered immunity against the bacterial pathogen Pseudomonas syringae pv. tomato strain DC3000 expressing avrRps4. The use of multiple stresses is a powerful tool to further define gene function. Here, we examined whether SRFR1 also impacts resistance to a herbivorous insect in leaves and to a cyst nematode in roots. Interestingly, srfr1-1 plants showed increased resistance to herbivory by the beet army worm Spodoptera exigua and to parasitism by the cyst nematode Heterodera schachtii compared with the corresponding wild-type Arabidopsis accession RLD. Using quantitative real-time PCR (qRT-PCR) to measure the transcript levels of salicylic acid (SA) and jasmonate/ethylene (JA/ET) pathway genes, we found that enhanced resistance of srfr1-1 plants to S. exigua correlated with specific upregulation of the MYC2 branch of the JA pathway concurrent with suppression of the SA pathway. In contrast, the greater susceptibility of RLD was accompanied by simultaneously increased transcript levels of SA, JA and JA/ET signalling pathway genes. Surprisingly, mutation of either SRFR1 or EDS1 increased resistance to H. schachtii, indicating that the concurrent presence of both wild-type genes promotes susceptibility. This finding suggests a novel form of resistance in Arabidopsis to the biotrophic pathogen H. schachtii or a root-specific regulation of the SA pathway by EDS1, and places SRFR1 at an intersection between multiple defence pathways.

Topics: Animals; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Down-Regulation; Feeding Behavior; Gene Expression Regulation, Plant; Herbivory; Oxylipins; Parasites; Plant Diseases; Plant Leaves; Plant Roots; RNA, Messenger; Salicylic Acid; Spodoptera; Tylenchoidea; Up-Regulation

Development of pathogen-resistant crops, such as fungus-resistant cotton, has significantly reduced chemical application and improved crop yield and quality. However, the mechanism of resistance to cotton pathogens such as Verticillium dahliae is still poorly understood. In this study, we characterized a cotton gene (HDTF1) that was isolated following transcriptome profiling during the resistance response of cotton to V. dahliae. HDTF1 putatively encodes a homeodomain transcription factor, and its expression was found to be down-regulated in cotton upon inoculation with V. dahliae and Botrytis cinerea. To characterise the involvement of HDTF1 in the response to these pathogens, we used virus-induced gene silencing (VIGS) to generate HDTF1-silenced cotton. VIGS reduction in HDTF1 expression significantly enhanced cotton plant resistance to both pathogens. HDTF1 silencing resulted in activation of jasmonic acid (JA)-mediated signaling and JA accumulation. However, the silenced plants were not altered in the accumulation of salicylic acid (SA) or the expression of marker genes associated with SA signaling. These results suggest that HDTF1 is a negative regulator of the JA pathway, and resistance to V. dahliae and B. cinerea can be engineered by activation of JA signaling.

Topics: Amino Acid Sequence; Botrytis; Cell Nucleus; Cyclopentanes; Disease Resistance; Down-Regulation; Gene Expression Regulation, Plant; Gene Knockdown Techniques; Gene Silencing; Genes, Plant; Gossypium; Homeodomain Proteins; Nicotiana; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plant Viruses; Salicylic Acid; Sequence Alignment; Sequence Analysis, DNA; Signal Transduction; Subcellular Fractions; Suppression, Genetic; Verticillium

Fruit ripening is a complex process that is regulated by a signal network. Whereas the regulatory mechanism of abscisic acid has been studied extensively in non-climacteric fruit, little is know about other signaling pathways involved in this process. In this study, we performed that plant hormone jasmonic acid plays an important role in grape fruit coloring and softening by increasing the transcription levels of several ripening-related genes, such as the color-related genes PAL1, DFR, CHI, F3H, GST, CHS, and UFGT; softening-related genes PG, PL, PE, Cell, EG1, and XTH1; and aroma-related genes Ecar, QR, and EGS. Lastly, the fruit anthocyanin, phenol, aroma, and cell wall materials were changed. Jasmonic acid positively regulated its biosynthesis pathway genes LOS, AOS, and 12-oxophytodienoate reductase (OPR) and signal pathway genes COI1 and JMT. RNA interference of grape jasmonic acid pathway gene VvAOS in strawberry fruit appeared fruit un-coloring phenotypes; exogenous jasmonic acid rescued this phenotypes. On the contrary, overexpression of grape jasmonic acid receptor VvCOI1 in the strawberry fruit accelerated the fruit-ripening process and induced some plant defense-related gene expression level. Furthermore, jasmonic acid treatment or strong jasmonic acid signal pathway in strawberry fruit make the fruit resistance against Botrytis cinerea.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Fragaria; Fruit; Genes, Plant; Oxylipins; Vitis

Plants respond to herbivory with the induction of resistance, mediated by distinct phytohormonal signaling pathways and their interactions. Phloem feeders are known to induce plant resistance via the salicylic acid pathway, whereas biting-chewing herbivores induce plant resistance mainly via the jasmonate pathway. Here, we show that a specialist caterpillar (biting-chewing herbivore) and a specialist aphid (phloem feeder) differentially induce resistance against Pieris brassicae caterpillars in Arabidopsis (Arabidopsis thaliana) plants. Caterpillar feeding induces resistance through the jasmonate signaling pathway that is associated with the induction of kaempferol 3,7-dirhamnoside, whereas aphid feeding induces resistance via a novel mechanism involving sinapoyl malate. The role of sinapoyl malate is confirmed through the use of a mutant compromised in the biosynthesis of this compound. Caterpillar-induced resistance is associated with a lower cost in terms of plant growth reduction than aphid-induced resistance. A strong constitutive resistance against P. brassicae caterpillars in combination with a strong growth attenuation in plants of a transfer DNA (T-DNA) insertion mutant of WRKY70 (wrky70) suggest that the WRKY70 transcription factor, a regulator of downstream responses mediated by jasmonate-salicylic acid signaling cross talk, is involved in the negative regulation of caterpillar resistance and in the tradeoff between growth and defense. In conclusion, different mechanisms of herbivore-induced resistance come with different costs, and a functional WRKY70 transcription factor is required for the induction of low-cost resistance.

Topics: Animals; Aphids; Arabidopsis; Arabidopsis Proteins; Biomass; Biosynthetic Pathways; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Glucosinolates; Herbivory; Kaempferols; Larva; Malates; Oxylipins; Phenylpropionates; RNA, Messenger; Salicylic Acid; Signal Transduction; Transcription Factors

The tomato Ve1 gene and several Ve1 homologues are involved in the resistance to Verticillium dahliae. Here, we report on another Ve homologous gene, Gbvdr3, from a Verticillium wilt-resistant cotton cultivar, Gossypium barbadense Hai7124, which has a 3207-bp region that encodes a predicted receptor-like protein. Transient expression analyses indicated that Gbvdr3 is localized in the plasma membrane, and virus-induced gene silencing of Gbvdr3 compromised the resistance of Hai7124 cotton to a defoliating strain of V. dahliae, V991, but not to a non-defoliating strain, BP2. This resistance pattern was further confirmed by over-expression of Gbvdr3 in transgenic Arabidopsis, which significantly elevated the expression of the ethylene-regulated gene GST2, the ethylene- and jasmonic acid-regulated defense-related genes PR3 and PDF1.2, and the salicylic acid-regulated genes PR1 and PR5, but not the PR2 gene. It also triggered the accumulation of hydrogen peroxide and callose at early time points during infection by the V991 defoliating strain. In contrast, elevated accumulation of hydrogen peroxide or callose in Gbvdr3-expressed Arabidopsis leaves was not apparent under infection by the non-defoliating strain, BP2. These results suggested that Gbvdr3 is involved in the resistance to a unique spectrum of defoliating V. dahliae strains.

Topics: Amino Acid Sequence; Arabidopsis; Base Sequence; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Gossypium; Hydrogen Peroxide; Molecular Sequence Data; Oxylipins; Phylogeny; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Seedlings; Sequence Alignment; Sequence Analysis, DNA; Verticillium

Gossypol is an important allelochemical produced by the subepidermal glands of some cotton varieties and important for their ability to respond to changing biotic stress by exhibiting antibiosis against some cotton pests. Plant growth-promoting rhizobacteria (PGPR) are root-colonizing bacteria that increase plant growth and often elicit defence against plant pathogens and insect pests. Little is known about the effect of PGPR on cotton plant-insect interactions and the potential biochemical and molecular mechanisms by which PGPR enhance cotton plant defence. Here, we report that PGPR (Bacillus spp.) treated cotton plants showed significantly higher levels of gossypol compared with untreated plants. Similarly, the transcript levels of the genes (i.e. (+)-δ-cadinene synthase gene family) involved in the biosynthesis of gossypol were higher in PGPR-treated plants than in untreated plants. Furthermore, the levels of jasmonic acid, an octadecanoid-derived defence-related phytohormone and the transcript level of jasmonic acid responsive genes were higher in PGPR-treated plants than in untreated plants. Most intriguingly, Spodoptera exigua showed reduced larval feeding and development on PGPR-treated plants. These findings demonstrate that treatment of plants with rhizobacteria may induce significant biochemical and molecular changes with potential ramifications for plant-insect interactions.

Topics: Animals; Body Weight; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Gossypium; Gossypol; Isomerases; Larva; Oxylipins; Plant Diseases; Real-Time Polymerase Chain Reaction; Rhizobium; Spodoptera

Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most devastating diseases in many important crops including Brassica napus worldwide. Quantitative resistance is the only source for genetic improvement of Sclerotinia-resistance in B. napus, but the molecular basis for such a resistance is largely unknown. Here, we performed dynamic transcriptomic analyses to understand the differential defense response to S. sclerotiorum in a resistant line (R-line) and a susceptible line (S-line) of B. napus at 24, 48 and 96 h post-inoculation. Both the numbers of and fold changes in differentially expressed genes in the R-line were larger than those in the S-line. We identified 9001 relative differentially expressed genes in the R-line compared with the S-line. The differences between susceptibility and resistance were associated with the magnitude of expression changes in a set of genes involved in pathogen recognition, MAPK signaling cascade, WRKY transcription regulation, jasmonic acid/ethylene signaling pathways, and biosynthesis of defense-related protein and indolic glucosinolate. The results were supported by quantitation of defense-related enzyme activity and glucosinolate contents. Our results provide insights into the complex molecular mechanism of the defense response to S. sclerotiorum in B. napus and for development of effective strategies in Sclerotinia-resistance breeding.

Topics: Ascomycota; Brassica napus; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Ontology; Gene Regulatory Networks; Glucosinolates; MAP Kinase Signaling System; Molecular Sequence Annotation; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plant Stems; Plants, Genetically Modified; Transcriptome

In the last decades, the plant innate immune responses against pathogens have been extensively studied, while biocontrol interactions between soilborne fungal pathogens and their hosts have received much less attention. Treatment of Arabidopsis thaliana with the nonpathogenic bacterium Paenibacillus alvei K165 was shown previously to protect against Verticillium dahliae by triggering induced systemic resistance (ISR). In the present study, we evaluated the involvement of the innate immune response in the K165-mediated protection of Arabidopsis against V. dahliae. Tests with Arabidopsis mutants impaired in several regulators of the early steps of the innate immune responses, including fls2, efr-1, bak1-4, mpk3, mpk6, wrky22, and wrky29 showed that FLS2 and WRKY22 have a central role in the K165-triggered ISR, while EFR1, MPK3, and MPK6 are possible susceptibility factors for V. dahliae and bak1 shows a tolerance phenomenon. The resistance induced by strain K165 is dependent on both salicylate and jasmonate-dependent defense pathways, as evidenced by an increased transient accumulation of PR1 and PDF1.2 transcripts in the aerial parts of infected plants treated with strain K165.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Defensins; Disease Resistance; Gene Expression Regulation, Plant; Models, Biological; Oxylipins; Paenibacillus; Pest Control, Biological; Plant Components, Aerial; Plant Diseases; Plant Growth Regulators; Salicylic Acid; Signal Transduction; Verticillium

Gibberellins are a class of tetracyclic plant hormones that are well known to promote plant growth by inducing the degradation of a class of nuclear growth-repressing proteins, called DELLAs. In recent years, GA and DELLAs are also increasingly implicated in plant responses to pathogen attack, although our understanding of the underlying mechanisms is still limited, especially in monocotyledonous crop plants. Aiming to further decipher the molecular underpinnings of GA- and DELLA-modulated plant immunity, we studied the dynamics and impact of GA and DELLA during infection of the model crop rice (Oryza sativa) with four different pathogens exhibiting distinct lifestyles and infection strategies. Opposite to previous findings in Arabidopsis (Arabidopsis thaliana), our findings reveal a prominent role of the DELLA protein Slender Rice1 (SLR1) in the resistance toward (hemi)biotrophic but not necrotrophic rice pathogens. Moreover, contrary to the differential effect of DELLA on the archetypal defense hormones salicylic acid (SA) and jasmonic acid (JA) in Arabidopsis, we demonstrate that the resistance-promoting effect of SLR1 is due at least in part to its ability to boost both SA- and JA-mediated rice defenses. In a reciprocal manner, we found JA and SA treatment to interfere with GA metabolism and stabilize SLR1. Together, these findings favor a model whereby SLR1 acts as a positive regulator of hemibiotroph resistance in rice by integrating and amplifying SA- and JA-dependent defense signaling. Our results highlight the differences in hormone defense networking between rice and Arabidopsis and underscore the importance of GA and DELLA in molding disease outcomes.

Topics: Ascomycota; Blotting, Western; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Magnaporthe; Mutation; Oryza; Oxylipins; Plant Diseases; Plant Immunity; Plant Proteins; Plants, Genetically Modified; Reverse Transcriptase Polymerase Chain Reaction; Rhizoctonia; Salicylic Acid; Signal Transduction; Species Specificity; Xanthomonas

Necrotrophic and biotrophic pathogens are resisted by different plant defenses. While necrotrophic pathogens are sensitive to jasmonic acid (JA)-dependent resistance, biotrophic pathogens are resisted by salicylic acid (SA)- and reactive oxygen species (ROS)-dependent resistance. Although many pathogens switch from biotrophy to necrotrophy during infection, little is known about the signals triggering this transition. This study is based on the observation that the early colonization pattern and symptom development by the ascomycete pathogen Plectosphaerella cucumerina (P. cucumerina) vary between inoculation methods. Using the Arabidopsis (Arabidopsis thaliana) defense response as a proxy for infection strategy, we examined whether P. cucumerina alternates between hemibiotrophic and necrotrophic lifestyles, depending on initial spore density and distribution on the leaf surface. Untargeted metabolome analysis revealed profound differences in metabolic defense signatures upon different inoculation methods. Quantification of JA and SA, marker gene expression, and cell death confirmed that infection from high spore densities activates JA-dependent defenses with excessive cell death, while infection from low spore densities induces SA-dependent defenses with lower levels of cell death. Phenotyping of Arabidopsis mutants in JA, SA, and ROS signaling confirmed that P. cucumerina is differentially resisted by JA- and SA/ROS-dependent defenses, depending on initial spore density and distribution on the leaf. Furthermore, in situ staining for early callose deposition at the infection sites revealed that necrotrophy by P. cucumerina is associated with elevated host defense. We conclude that P. cucumerina adapts to early-acting plant defenses by switching from a hemibiotrophic to a necrotrophic infection program, thereby gaining an advantage of immunity-related cell death in the host.

Topics: Arabidopsis; Ascomycota; Cell Death; Cyclopentanes; Disease Resistance; Metabolic Networks and Pathways; Metabolome; Metabolomics; Models, Biological; Oxylipins; Phenotype; Plant Diseases; Plant Leaves; Reactive Oxygen Species; Salicylic Acid; Spores, Fungal; Thiadiazoles

Downy mildew caused by Sclerospora graminicola is a devastating disease of pearl millet. Based on candidate gene approach, a set of 22 resistance gene analogues were identified. The clone RGPM 301 (AY117410) containing a partial sequence shared 83% similarity to rice R-proteins. A full-length R-gene RGA RGPM 301 of 3552 bp with 2979 bp open reading frame encoding 992 amino acids was isolated by the degenerate primers and rapid amplification of cDNA ends polymerase chain reaction (RACE-PCR) approach. It had a molecular mass of 113.96 kDa and isoelectric point (pI) of 8.71. The sequence alignment and phylogenetic analysis grouped it to a non-TIR NBS LRR group. The quantitative real-time PCR (qRT-PCR) analysis revealed higher accumulation of the transcripts following inoculation with S. graminicola in the resistant cultivar (IP18296) compared to susceptible cultivar (7042S). Further, significant induction in the transcript levels were observed when treated with abiotic elicitor β-aminobutyric acid (BABA) and biotic elicitor Pseudomonas fluorescens. Exogenous application of phytohormones jasmonic acid or salicylic acid also up-regulated the expression levels of RGA RGPM 301. The treatment of cultivar IP18296 with mitogen-activated protein kinase (MPK) inhibitors (PD98059 and U0126) suppressed the levels of RGA RGPM 301. A 3.5 kb RGA RGPM 301 which is a non-TIR NBS-LRR protein was isolated from pearl millet and its up-regulation during downy mildew interaction was demonstrated by qRT-PCR. These studies indicate a role for this RGA in pearl millet downy mildew interaction.

Topics: Amino Acid Sequence; Aminobutyrates; Bacterial Proteins; Base Sequence; Cenchrus; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Molecular Sequence Data; Oomycetes; Oxylipins; Pennisetum; Phylogeny; Plant Diseases; Plant Proteins; Pseudomonas fluorescens; Salicylic Acid; Sequence Alignment; Up-Regulation

Understanding how plants allocate their resources to growth or defence is of long-term importance to the development of new and improved varieties of different crops. Using molecular genetics, plant physiology, hormone analysis and Next-Generation Sequencing (NGS)-based transcript profiling, we have isolated and characterized the rice (Oryza sativa) LESION AND LAMINA BENDING (LLB) gene that encodes a chloroplast-targeted putative leucine carboxyl methyltransferase. Loss of LLB function results in reduced growth and yield, hypersensitive response (HR)-like lesions, accumulation of the antimicrobial compounds momilactones and phytocassanes, and constitutive expression of pathogenesis-related genes. Consistent with these defence-associated responses, llb shows enhanced resistance to rice blast (Magnaporthe oryzae) and bacterial blight (Xanthomonas oryzae pv. oryzae). The lesion and resistance phenotypes are likely to be caused by the over-accumulation of jasmonates (JAs) in the llb mutant including the JA precursor 12-oxo-phytodienoic acid. Additionally, llb shows an increased lamina inclination and enhanced early seedling growth due to elevated brassinosteroid (BR) synthesis and/or signalling. These findings show that LLB functions in the chloroplast to either directly or indirectly repress both JA- and BR-mediated responses, revealing a possible mechanism for controlling how plants allocate resources for defence and growth.

Topics: Amino Acid Sequence; Chloroplasts; Cyclopentanes; Disease Resistance; Fatty Acids, Unsaturated; Genes, Reporter; Magnaporthe; Mutation; Oryza; Oxylipins; Phenotype; Plant Diseases; Plant Growth Regulators; Plant Leaves; Seedlings; Xanthomonas

In Arabidopsis, jasmonate (JA)-signaling plays a key role in mediating Fusarium oxysporum disease outcome. However, the roles of JASMONATE ZIM-domain (JAZ) proteins that repress JA-signaling have not been characterized in host resistance or susceptibility to this pathogen. Here, we found most JAZ genes are induced following F. oxysporum challenge, and screening T-DNA insertion lines in Arabidopsis JAZ family members identified a highly disease-susceptible JAZ7 mutant (jaz7-1D). This mutant exhibited constitutive JAZ7 expression and conferred increased JA-sensitivity, suggesting activation of JA-signaling. Unlike jaz7 loss-of-function alleles, jaz7-1D also had enhanced JA-responsive gene expression, altered development and increased susceptibility to the bacterial pathogen PstDC3000 that also disrupts host JA-responses. We also demonstrate that JAZ7 interacts with transcription factors functioning as activators (MYC3, MYC4) or repressors (JAM1) of JA-signaling and contains a functional EAR repressor motif mediating transcriptional repression via the co-repressor TOPLESS (TPL). We propose through direct TPL recruitment, in wild-type plants JAZ7 functions as a repressor within the JA-response network and that in jaz7-1D plants, misregulated ectopic JAZ7 expression hyper-activates JA-signaling in part by disturbing finely-tuned COI1-JAZ-TPL-TF complexes.

Topics: Amino Acid Motifs; Arabidopsis; Arabidopsis Proteins; Co-Repressor Proteins; Cyclopentanes; Disease Resistance; Disease Susceptibility; DNA, Bacterial; Flowers; Fusarium; Gene Expression Regulation, Plant; Genes, Plant; Models, Biological; Mutagenesis, Insertional; Mutation; Oligonucleotide Array Sequence Analysis; Oxylipins; Phenotype; Plant Diseases; Plants, Genetically Modified; Protein Binding; Pseudomonas syringae; Repressor Proteins; RNA, Messenger; Up-Regulation

The green peach aphid, Myzus persicae Sulzer, is a notorious pest on vegetables, which often aggregates in high densities on crop leaves. In this study, we investigated whether M. persicae could suppress the resistance level of Chinese cabbage Brassica pekinensis. M. persicae performed better in terms of weight gain (~33% increase) and population growth (~110% increase) when feeding on previously infested (pre-infested) Chinese cabbage compared with those on non-infested plants. However, when given a choice, 64% of the aphids preferred to settle on non-infested leaves, while 29% of aphids chose pre-infested leaves that had a 2.9 times higher concentration of glucosinolates. Aphid feeding significantly enhanced the amino acid:sugar ratio of phloem sap and the absolute amino acid concentration in plant leaves. Aphid infestation significantly increased the expression levels of salicylic acid (SA) marker genes, while it had marginal effects on the expression of jasmonate marker genes. Exogenously applied SA or methyl jasmonate had no significant effects on M. persicae performance, although these chemicals increased glucosinolates concentration in plant leaves. M. persicae infestation increase amino acid:sugar ratio and activate plant defenses, but aphid performed better on pre-infested plants, suggesting that both nutrition and toxics should be considered in insect-plant interaction.

Topics: Amino Acids; Animals; Aphids; Brassica; Cyclopentanes; Disease Resistance; Feeding Behavior; Gene Expression Regulation, Plant; Genes, Plant; Glucosinolates; Host-Parasite Interactions; Oxylipins; Phloem; Plant Diseases; Plant Leaves; Prunus persica; Salicylic Acid

Allantoin is a metabolic intermediate of purine catabolism that often accumulates in stressed plants. Recently, we used Arabidopsis knockout mutants (aln) of ALLANTOINASE to show that this purine metabolite activates abscisic acid (ABA) production, thereby stimulating stress-related gene expression and enhancing seedling tolerance to abiotic stress. A detailed re-examination of the microarray data of an aln mutant (aln-1) confirmed the increased expression of ABA-related genes and also revealed altered expression of genes involved in jasmonic acid (JA) responses, probably under the control of MYC2, a master switch in the JA signaling pathway. Consistent with the transcriptome profiles, the aln-1 mutant displayed increased JA levels and enhanced responses to mechanical wounding and exogenous JA. Moreover, aln mutants demonstrated modestly increased susceptibility to Pseudomonas syringae and Pectobacterium carotovorum, probably reflecting the antagonistic action of MYC2 on the defense against these bacterial phytopathogens. Exogenously administered allantoin elicited the expression of JA-responsive genes, including MYC2, in wild-type plants, supporting the idea that allantoin might be responsible for the observed JA-related phenotypes of aln mutants. However, mutants deficient in bioactive JA (jar1-1), insensitive to JA (myc2-3), or deficient in ABA (aba2-1 and bglu18) suppressed the effect of exogenous allantoin. The suppression was further confirmed in aln-1 jar1-1 and aln-1 bglu18 double mutants. These results indicate that allantoin can activate the MYC2-regulated JA signaling pathway through ABA production. Overall, this study suggests a possible connection of purine catabolism with stress hormone homeostasis and signaling, and highlights the potential importance of allantoin in these interactions.

Topics: Abscisic Acid; Allantoin; Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Isoleucine; Metabolome; Mutation; Oxylipins; Pectobacterium; Plant Diseases; Pseudomonas syringae; Purines; Salicylic Acid; Signal Transduction; Stress, Physiological

OsPGIP4 overexpression enhances resistance to bacterial leaf streak in rice. Polygalacturonase-inhibiting proteins are thought to play important roles in the innate immunity of rice against fungi. Here, we show that the chromosomal location of OsPGIP4 coincides with the major bacterial leaf streak resistance quantitative trait locus qBlsr5a on the short arm of chromosome 5. OsPGIP4 expression was up-regulated upon inoculation with the pathogen Xanthomonas oryzae pv. oryzicola strain RS105. OsPGIP4 overexpression enhanced the resistance of the susceptible rice variety Zhonghua 11 to RS105. In contrast, repressing OsPGIP4 expression resulted in an increase in disease lesions caused by RS105 in Zhonghua 11 and in Acc8558, a qBlsr5a resistance donor. More interestingly, upon inoculation, the activated expression of pathogenesis-related genes was attenuated for those genes involved in the salicylic acid pathway, while the activated expression of jasmonic acid pathway markers was increased in the overexpression lines. Our results not only provide the first report that rice PGIP could enhance resistant against a bacterial pathogen but also indicate that OsPGIP4 is a potential component of the qBlsr5a locus for bacterial leaf streak in rice.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Xanthomonas

The plant hormones jasmonic acid (JA) and salicylic acid (SA) play key roles in plant defenses against pathogens and several WRKY transcription factors have been shown to have a role in SA/JA crosstalk. In a previous study, overexpression of the poplar WRKY gene PtrWRKY89 enhanced resistance to pathogens in transgenic poplars. In this study, the promoter of PtrWRKY89 (ProPtrWRKY89) was isolated and used to drive GUS reporter gene. High GUS activity was observed in old leaves of transgenic Arabidopsis containing ProPtrWRKY89-GUS construct and GUS expression was extremely induced by SA solution and SA+MeJA mixture but not by MeJA treatment. Subcellular localization and transactivation assays showed that PtrWRKY89 acted as a transcription activator in the nucleus. Constitutive expression of PtrWRKY89 in Arabidopsis resulted in more susceptible to Pseudomonas syringae and Botrytis cinerea compared to wild-type plants. Quantitative real-time PCR (qRT-PCR) analysis confirmed that marker genes of SA and JA pathways were down-regulated in transgenic Arabidopsis after pathogen inoculations. Overall, our results indicated that PtrWRKY89 modulates a cross talk in resistance to P. syringe and B. cinerea by negatively regulating both SA and JA pathways in Arabidopsis.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Chlorophyll; Cyclopentanes; Disease Resistance; Down-Regulation; Genes, Reporter; Hydrogen Peroxide; Oxylipins; Phenotype; Plant Leaves; Plants, Genetically Modified; Promoter Regions, Genetic; Pseudomonas syringae; Real-Time Polymerase Chain Reaction; RNA, Plant; Salicylic Acid; Signal Transduction; Transcriptional Activation; Transcriptome

Plant-microbe mutualisms can improve plant defense, but the impact of root endophytes on below-ground herbivore interactions remains unknown. We investigated the effects of the root endophyte Piriformospora indica on interactions between rice (Oryza sativa) plants and its root herbivore rice water weevil (RWW; Lissorhoptrus oryzophilus), and how plant jasmonic acid (JA) and GA regulate this tripartite interaction. Glasshouse experiments with wild-type rice and coi1-18 and Eui1-OX mutants combined with nutrient, jasmonate and gene expression analyses were used to test: whether RWW adult herbivory above ground influences subsequent damage caused by larval herbivory below ground; whether P. indica protects plants against RWW; and whether GA and JA signaling mediate these interactions. The endophyte induced plant tolerance to root herbivory. RWW adults and larvae acted synergistically via JA signaling to reduce root growth, while endophyte-elicited GA biosynthesis suppressed the herbivore-induced JA in roots and recovered plant growth. Our study shows for the first time the impact of a root endophyte on plant defense against below-ground herbivores, adds to growing evidence that induced tolerance may be an important root defense, and implicates GA as a signal component of inducible plant tolerance against biotic stress.

Topics: Adaptation, Physiological; Animals; Basidiomycota; Cyclopentanes; Disease Resistance; Endophytes; Gibberellins; Herbivory; Larva; Oryza; Oxylipins; Plant Development; Plant Diseases; Plant Roots; Signal Transduction; Weevils

Verticillium wilt is a disastrous vascular disease in plants caused by Verticillium dahliae. Verticillium pathogens secrete various disease-causing effectors in cotton. This study identified a subtilase gene GbSBT1 from Gossypium babardense and investigated the roles against V. dahliae infection. GbSBT1 gene expression is responsive to V. dahliae defense signals, jasmonic acid, and ethylene treatments. Moreover, the GbSBT1 protein is mainly localized in the cell membrane and moves into the cytoplasm following jasmonic acid and ethylene treatments. Silencing GbSBT1 gene expression through virus-induced GbSBT1 gene silencing reduced the tolerance of Pima-90 (resistant genotype), but not facilitated the infection process of V. dahliae in Coker-312 (sensitive genotype). Moreover, the ectopically expressed GbSBT1 gene enhanced the resistance of Arabidopsis to Fusarium oxysporum and V. dahliae infection and activated the expression levels of defense-related genes. Furthermore, pull-down, yeast two-hybrid assay, and BiFC analysis revealed that GbSBT1 interacts with a prohibitin (PHB)-like protein expressed in V. dahliae pathogens during infection. In summary, GbSBT1 recognizes the effector PHB protein secreted from V. dahliae and is involved in Verticillium-induced resistance in cotton.

Topics: Amino Acid Sequence; Arabidopsis; Cyclopentanes; Disease Resistance; Gossypium; Host-Pathogen Interactions; Molecular Sequence Data; Oxylipins; Phylogeny; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Sequence Homology, Amino Acid; Subtilisins; Two-Hybrid System Techniques; Verticillium

The WRKY family of transcription factors (TFs) functions as transcriptional activators or repressors in various signaling pathways. In this study, we discovered that OsWRKY62 and OsWRKY76, two genes of the WRKY IIa subfamily, undergo constitutive and inducible alternative splicing. The full-length OsWRKY62.1 and OsWRKY76.1 proteins formed homocomplexes and heterocomplexes, and the heterocomplex dominates in the nuclei when analyzed in Nicotiana benthamiana leaves. Transgenic overexpression of OsWRKY62.1 and OsWRKY76.1 in rice (Oryza sativa) enhanced plant susceptibility to the blast fungus Magnaporthe oryzae and the leaf blight bacterium Xanthomonas oryzae pv oryzae, whereas RNA interference and loss-of-function knockout plants exhibited elevated resistance. The dsOW62/76 and knockout lines of OsWRKY62 and OsWRKY76 also showed greatly increased expression of defense-related genes and the accumulation of phytoalexins. The ratio of full-length versus truncated transcripts changed in dsOW62/76 plants as well as in response to pathogen infection. The short alternative OsWRKY62.2 and OsWRKY76.2 isoforms could interact with each other and with full-length proteins. OsWRKY62.2 showed a reduced repressor activity in planta, and two sequence determinants required for the repressor activity were identified in the amino terminus of OsWRKY62.1. The amino termini of OsWRKY62 and OsWRKY76 splice variants also showed reduced binding to the canonical W box motif. These results not only enhance our understanding of the DNA-binding property, the repressor sequence motifs, and the negative feedback regulation of the IIa subfamily of WRKYs but also provide evidence for alternative splicing of WRKY TFs during the plant defense response.

Topics: Alternative Splicing; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Knockout Techniques; Genes, Plant; Magnaporthe; Mutation; Oryza; Oxylipins; Pathogen-Associated Molecular Pattern Molecules; Plant Diseases; Plant Immunity; Plant Proteins; Plants, Genetically Modified; Promoter Regions, Genetic; Protein Binding; Protein Isoforms; Repressor Proteins; RNA Interference; Transcription Factors; Xanthomonas

WRKY transcription factors play a central role not only in plant growth and development but also in plant stress responses. However, the role of WRKY transcription factors in herbivore-induced plant defenses and their underlying mechanisms, especially in rice, remains largely unclear. Here, we cloned a rice WRKY gene OsWRKY45, whose expression was induced by mechanical wounding, by infestation of the brown planthopper (BPH, Nilaparvata lugens) and by treatment with jasmonic acid (JA) or salicylic acid (SA). The antisense expression of OsWRKY45 (as-wrky) enhanced BPH-induced levels of H₂O₂ and ethylene, reduced feeding and oviposition preference as well as the survival rate of BPH, and delayed the development of BPH nymphs. Consistently, lower population densities of BPH on as-wrky lines, compared to those on wild-type (WT) plants, were observed in field experiments. On the other hand, as-wrky lines in the field had lower susceptibility to sheath blight (caused by Rhizoctonia solani) but higher susceptibility to rice blast (caused by Magnaporthe oryzae) than did WT plants. These findings suggest that OsWRKY45 plays important but contrasting roles in regulating the resistance of rice to pathogens and herbivores, and attention should be paid if OsWRKY45 is used to develop disease or herbivore-resistant rice.

Topics: Animals; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Hemiptera; Oryza; Oxylipins; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Transcription Factors

Although necrotrophic pathogens cause many devastating plant diseases, our understanding of the plant defense response to them is limited. Here, we found that loss of function of WRKY57 enhanced the resistance of Arabidopsis (Arabidopsis thaliana) against Botrytis cinerea infection. Further investigation suggested that the negative regulation of WRKY57 against B cinerea depends on the jasmonic acid (JA) signaling pathway. Chromatin immunoprecipitation experiments revealed that WRKY57 directly binds to the promoters of JASMONATE ZIM-DOMAIN1 (JAZ1) and JAZ5, encoding two important repressors of the JA signaling pathway, and activates their transcription. In vivo and in vitro experiments demonstrated that WRKY57 interacts with nuclear-encoded SIGMA FACTOR BINDING PROTEIN1 (SIB1) and SIB2. Further experiments display that the same domain, the VQ motif, of SIB1 and SIB2 interact with WRKY33 and WRKY57. Moreover, transient transcriptional activity assays confirmed that WRKY57 and WRKY33 competitively regulate JAZ1 and JAZ5, SIB1 and SIB2 further enhance these competitions of WRKY57 to WRKY33. Therefore, coordinated regulation of Arabidopsis against B cinerea by transcription activators and repressors would benefit plants by allowing fine regulation of defense.

Topics: Amino Acid Sequence; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Oxylipins; Plant Diseases; Protein Binding; Protein Domains; Signal Transduction; Stress, Physiological; Structure-Activity Relationship; Transcription Factors; Transcription, Genetic; Zinc Fingers

JASMONATE ZIM-domain (JAZ) proteins act as transcriptional repressors of jasmonic acid (JA) responses and play a crucial role in the regulation of host immunity in plants. Here, we report that OsMYC2, a JAZ-interacting transcription factor in rice (Oryza sativa L.), plays an important role in the resistance response against rice bacterial blight, which is one of the most serious diseases in rice, caused by Xanthomonas oryzae pv. oryzae (Xoo). The results showed that OsMYC2 interacted with some OsJAZ proteins in a JAZ-interacting domain (JID)-dependent manner. The up-regulation of OsMYC2 in response to JA was regulated by OsJAZ8. Transgenic rice plants overexpressing OsMYC2 exhibited a JA-hypersensitive phenotype and were more resistant to Xoo. A large-scale microarray analysis revealed that OsMYC2 up-regulated OsJAZ10 as well as many other defense-related genes. OsMYC2 selectively bound to the G-box-like motif of the OsJAZ10 promoter in vivo and regulated the expression of early JA-responsive genes, but not of late JA-responsive genes. The nuclear localization of OsMYC2 depended on a nuclear localization signal within JID. Overall, we conclude that OsMYC2 acts as a positive regulator of early JA signals in the JA-induced resistance against Xoo in rice.

Topics: Cell Nucleus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Promoter Regions, Genetic; Transcription Factors; Up-Regulation; Xanthomonas

Caffeine, the major purine alkaloid in tea has long been known for its role in plant defense. However, its effect on Colletotrichum gloeosporioides that causes brown blight disease in tea is largely unknown especially under elevated CO

Topics: Caffeine; Camellia sinensis; Carbon Dioxide; Colletotrichum; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Lipoxygenases; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Seedlings

Dual function of GhATAF1 in the responses to salinity stress and Verticillium dahliae infection in cotton. NAC (NAM/ATAF1/2/CUC2) is a large plant-specific transcription factor family that plays important roles in the response to abiotic stresses. We previously isolated a cotton NAC transcription factor gene, GhATAF1, which was up-regulated by ABA, cold and salt stresses and classified into AFAT1/2, a sub-family of NAC. Here, we report that GhATAF1 was also highly induced by MeJA, SA and Verticillium dahliae inoculation, which implied that GhATAF1 was involved not only in the response to abiotic stress but also in the response to biotic stress. GhATAF1 was localized in the nucleus and possessed transactivation activity. Overexpression of GhATAF1 enhanced cotton plant tolerance to salt stress by enhancing the expression of various stress-related genes, including the ABA response gene GhABI4; the transporter gene GhHKT1, involved in Na(+)/K(+) homeostasis; and several stress-response genes (GhAVP1, GhRD22, GhDREB2A, GhLEA3, and GhLEA6). Additionally, overexpressing GhATAF1 increased cotton plant susceptibility to the fungal pathogens V. dahliae and Botrytis cinerea, coupled with the suppression of JA-mediated signaling and the activation of SA-mediated signaling. Our results suggested that GhATAF1, the cotton stress-responsive NAC transcription factor, plays important roles in the response to both abiotic stress and biotic stress by coordinating the phytohormone signaling networks.

Topics: Amino Acid Sequence; Arabidopsis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gossypium; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Salt Tolerance; Sequence Alignment; Signal Transduction; Stress, Physiological; Subcellular Fractions; Transcription Factors; Transcriptional Activation; Verticillium

ERF transcription factors play critical roles in plant immune responses. Here, we report the function of AtERF014, a nucleus-localized transcriptional activator, in Arabidopsis immunity. Expression of AtERF014 was induced by Pseudomonas syringae pv. tomato (Pst) and Botrytis cinerea (Bc). AtERF014-overexpressing (OE) plants displayed increased Pst resistance but decreased Bc resistance, whereas AtERF014-RNAi plants exhibited decreased Pst resistance but increased Bc resistance. After Pst infection, expression of salicylic acid (SA)-responsive genes AtPR1 and AtPR5 in AtERF014-OE plants and of a jasmonic acid/ethylene-responsive gene AtPDF1.2 in AtERF014-RNAi plants was intensified but expression of AtPDF1.2 in AtERF014-OE plants and of AtPR1 and AtPR5 in AtERF014-RNAi plants was weakened. After Bc infection, expression of AtPR1 and AtPR5 in AtERF014-OE plants was attenuated but expression of AtPR1, AtPR5 and AtPDF1.2 in AtERF014-RNAi plants was strengthened. Pathogen- and flg22-induced ROS burst, expression of PTI genes and SA-induced defense were partially suppressed in AtERF014-RNAi plants, whereas pathogen-induced ROS and flg22-induced immune response were strengthened in AtER014-OE plants. Altered expression of AtERR014 affected expression of pectin biosynthetic genes and pectin content in AtERF014-RNAi plants was decreased. These data demonstrate that AtERF014 acts as a dual regulator that differentially modulates immunity against Pst and Bc in Arabidopsis.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Defensins; Disease Resistance; DNA-Binding Proteins; Ethylenes; Gene Expression Regulation, Plant; Oxylipins; Pectins; Plant Diseases; Plant Immunity; Pseudomonas syringae; Salicylic Acid; Transcription Factors

The cytochrome P450 monooxygenases (P450s) represent a large and important enzyme superfamily in plants. They catalyze numerous monooxygenation/hydroxylation reactions in biochemical pathways, P450s are involved in a variety of metabolic pathways and participate in the homeostasis of phytohormones. The CYP82 family genes specifically reside in dicots and are usually induced by distinct environmental stresses. However, their functions are largely unknown, especially in soybean (Glycine max L.). Here, we report the function of GmCYP82A3, a gene from soybean CYP82 family. Its expression was induced by Phytophthora sojae infection, salinity and drought stresses, and treatment with methyl jasmonate (MeJA) or ethephon (ETH). Its expression levels were consistently high in resistant cultivars. Transgenic Nicotiana benthamiana plants overexpressing GmCYP82A3 exhibited strong resistance to Botrytis cinerea and Phytophthora parasitica, and enhanced tolerance to salinity and drought stresses. Furthermore, transgenic plants were less sensitive to jasmonic acid (JA), and the enhanced resistance was accompanied with increased expression of the JA/ET signaling pathway-related genes.

Topics: Cyclopentanes; Cytochrome P-450 Enzyme System; Disease Resistance; Droughts; Ethylenes; Gene Expression Regulation, Plant; Glycine max; Oxylipins; Phytophthora; Plant Diseases; Signal Transduction; Stress, Physiological

This is the first report that GLP gene (OsGLP2-1) is involved in panicle blast and bacterial blight resistance in rice. In addition to its resistance to blast and bacterial blight, OsGLP2-1 has also been reported to co-localize with a QTLs for sheath blight resistance in rice. These suggest that the disease resistance provided by OsGLP2-1 is quantitative and broad spectrum. Its good resistance to these major diseases in rice makes it to be a promising target in rice breeding. Rice (Oryza sativa) blast caused by Magnaporthe oryzae and bacterial blight caused by Xanthomonas oryzae pv. oryzae are the two most destructive rice diseases worldwide. Germin-like protein (GLP) gene family is one of the important defense gene families which have been reported to be involved in disease resistance in plants. Although GLP proteins have been demonstrated to positively regulate leaf blast resistance in rice, their involvement in resistance to panicle blast and bacterial blight, has not been reported. In this study, we reported that one of the rice GLP genes, OsGLP2-1, was significantly induced by blast fungus. Overexpression of OsGLP2-1 quantitatively enhanced resistance to leaf blast, panicle blast and bacterial blight. The temporal and spatial expression analysis revealed that OsGLP2-1is highly expressed in leaves and panicles and sub-localized in the cell wall. Compared with empty vector transformed (control) plants, the OsGLP2-1 overexpressing plants exhibited higher levels of H

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glycoproteins; Hydrogen Peroxide; Magnaporthe; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Xanthomonas

Stilbenes are central phytoalexins in Vitis, and induction of the key enzyme stilbene synthase (STS) is pivotal for disease resistance. Here, we address the potential for breeding resistance using an STS allele isolated from Chinese wild grapevine Vitis pseudoreticulata (VpSTS) by comparison with its homologue from Vitis vinifera cv. 'Carigane' (VvSTS). Although the coding regions of both alleles are very similar (>99% identity on the amino acid level), the promoter regions are significantly different. By expression in Arabidopsis as a heterologous system, we show that the allele from the wild Chinese grapevine can confer accumulation of stilbenes and resistance against the powdery mildew Golovinomyces cichoracearum, whereas the allele from the vinifera cultivar cannot. To dissect the upstream signalling driving the activation of this promoter, we used a dual-luciferase reporter system in a grapevine cell culture. We show elevated responsiveness of the promoter from the wild grape to salicylic acid (SA) and to the pathogen-associated molecular pattern (PAMP) flg22, equal induction of both alleles by jasmonic acid (JA), and a lack of response to the cell death-inducing elicitor Harpin. This elevated SA response of the VpSTS promoter depends on calcium influx, oxidative burst by RboH, mitogen-activated protein kinase (MAPK) signalling, and JA synthesis. We integrate the data in the context of a model where the resistance of V. pseudoreticulata is linked to a more efficient recruitment of SA signalling for phytoalexin synthesis.

Topics: Acyltransferases; Alleles; Ascomycota; Cyclopentanes; Disease Resistance; Oxylipins; Plant Growth Regulators; Plant Proteins; Promoter Regions, Genetic; Salicylic Acid; Signal Transduction; Vitis

Wheat stem rust, caused by Puccinia graminis f. sp. tritici, is a major wheat disease which is mainly controlled through the release of resistant cultivars containing one or several resistance genes. Considerable effort has been put into the discovery of new resistance genes, but knowledge of their mechanisms of action is often lacking. In this study, the mechanism of resistance conferred by a recently discovered stem rust resistance locus on wheat chromosome 7AL was investigated through microscopic observations and RNA-sequencing, using the susceptible line Columbus and the independent, backcrossed, resistant lines Columbus-NS765 and Columbus-NS766.. Microscopic observations of infected leaves revealed that the resistance conferred by the 7AL resistance locus was initiated 2 days post-inoculation, upon the fungus entry into the plant through the stoma. Resistance was manifested by death of guard and epidermal cells adjacent to an infection site. Occasionally, similar observations were made in the susceptible line, suggesting that the resistance response was the same in all genotypes, but enhanced in the resistant lines. Transcriptomic analysis, combined with assignment of genes to wheat chromosomes, revealed a disproportionately high number of differentially expressed genes were located on chromosomes 7AL and 6A. A number of genes annotated as cysteine-rich receptor-like kinases were located on chromosome 7AL. Closer investigation indicated that the encoded proteins were in fact putative receptor-like cytoplasmic kinases. One of the putative RLCK genes contained a SNP marker previously shown to co-segregate with the 7AL resistance locus. The results also indicated the presence of a large introgression on chromosome 6A in both resistant lines, but whether it has any role in the resistance response is unclear.. This study represents the first investigation on the resistance mechanism conferred by the wheat 7AL stem rust resistance locus. The resistance response was associated with pre-haustorial cell death, and the transcriptome analysis suggested putative receptor-like cytoplasmic kinases as candidate resistance genes for further investigation.

Topics: Basidiomycota; Chromosome Mapping; Chromosomes, Plant; Cyclopentanes; Disease Resistance; Fluorescein-5-isothiocyanate; Genes, Plant; Oxylipins; Phenotype; Plant Diseases; Polymorphism, Single Nucleotide; Salicylic Acid; Sequence Analysis, RNA; Signal Transduction; Transcriptome; Triticum

Mutant T66 was isolated from 450 mutants (constructed with Agrobacterium tumefaciens-mediated transformation method) of Trichoderma harzianum. Maize seeds coated with T66 were more susceptible to Curvularia lunata when compared with those coated with wild-type (WT) strain. The disease index of maize treated with T66 and WT were 62.5 and 42.1%, respectively. Further research showed T-DNA has inserted into the ORF of one gene, which resulted in the functional difference between WT and T66. The gene was cloned and named Thc6, which encodes a novel 327 amino acid protein. To investigate its function, we obtained knockout, complementation, and overexpression mutants of Thc6. Challenge inoculation studies suggested that the Thc6 overexpression mutant can reduce the disease index of maize inbred line Huangzao 4 against the leaf spot pathogen (C. lunata). Meanwhile, The Thc6 mutants were found to affect the resistance of maize inbred line Huangzao 4 against C. lunata by enhancing the activation of jasmonate-responsive genes expression. Liquid chromatography-mass spectrometry (LC-MS) data further confirmed that the concentration of jasmonate in the induced maize exhibits a parallel change tendency with the expression level of defense-related genes. Hence, the Thc6 gene could be participated in the induced resistance of maize inbred line Huangzao 4 against C. lunata infection through a jasmonic acid-dependent pathway.

Topics: Ascomycota; Cyclopentanes; Disease Resistance; Fungal Proteins; Gene Expression; Gene Knockout Techniques; Genetic Complementation Test; Mutagenesis, Insertional; Oxylipins; Plant Diseases; Trichoderma; Zea mays

We recently characterized a highly dynamic fungal disease outbreak in native populations of Nicotiana attenuata in the southwestern United States. Here, we explore how phytohormone signalling contributes to the observed disease dynamics. Single inoculation with three native Fusarium and Alternaria fungal pathogens, isolated from diseased plants growing in native populations, resulted in disease symptoms characteristic for each pathogen species. While Alternaria sp.-infected plants displayed fewer symptoms and recovered, Fusarium spp.-infected plants became chlorotic and frequently spontaneously wilted. Jasmonic acid (JA) and salicylic acid (SA) levels were differentially induced after Fusarium or Alternaria infection. Transgenic N. attenuata lines silenced in JA production or JA conjugation to isoleucine (JA-Ile), but not in JA perception, were highly susceptible to infection by F. brachygibbosum Utah 4, indicating that products derived from the JA-Ile biosynthetic pathway, but not their perception, is associated with increased Fusarium resistance. Infection assays using ov-nahG plants which were silenced in pathogen-induced SA accumulations revealed that SA may increase N. attenuata's resistance to Fusarium infection but not to Alternaria. Taken together, we propose that the dynamics of fungal disease symptoms among plants in native populations may be explained by a complex interplay of phytohormone responses to attack by multiple pathogens.

Topics: Alternaria; Cyclopentanes; Disease Resistance; Fusarium; Host-Pathogen Interactions; Isoleucine; Nicotiana; Oxylipins; Plant Diseases; Plant Growth Regulators; Salicylic Acid; Signal Transduction

Tomato plants colonised with the arbuscular mycorrhizal (AM) fungus Glomus fasciculatum show systemic induced resistance to the foliar pathogen Alternaria alternata, as observed in interactions of other AM-colonised plants with a range of pathogens. The role of jasmonic (JA) and salicylic (SA) acid in expression of this mycorrhiza-induced resistance (MIR) against A. alternata was studied by measuring: (i) activity of enzymes reported to be involved in their biosynthesis, namely lipoxygenase (LOX) and phenylammonia lyase (PAL); and (ii) levels of methyl jasmonate (MeJA) and SA. Transcript abundance of some defence genes associated with JA and SA response pathways were also studied. Both LOX and PAL activity increased twofold in response to pathogen application to control plants. AM-colonised plants had three-fold higher LOX activity compared to control plants, but unlike controls, this did not increase further in response to pathogen application. Higher LOX activity in AM-colonised plants correlated with four-fold higher MeJA in leaves of AM-colonised plants compared to controls. Treatment of plants with the JA biosynthesis inhibitor salicylhydroxamic acid (SHAM) led to 50% lower MeJA in both control and AM-colonised plants and correlated with increased susceptibility to A. alternata, suggesting a causal role for JA in expression of MIR against the pathogen. Genes involved in JA biosynthesis (OPR3) and response (COI1) showed six- and 42-fold higher expression, respectively, in leaves of AM-colonised plants compared to controls. AM-colonised plants also showed increased expression of the SA response gene PR1 and that of the wound-inducible polypeptide prosystemin. Our results suggest that the systemic increase in JA in response to AM colonisation plays a key role in expression of MIR against A. alternata.

Topics: Acetates; Alternaria; Cyclopentanes; Disease Resistance; Genes, Plant; Glomeromycota; Lipoxygenase; Lyases; Mycorrhizae; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Salicylic Acid; Solanum lycopersicum

Mechanical wounding or treatment with exogenous jasmonates (JA) induces differentiation of the laticifer in Hevea brasiliensis. JA is a key signal for latex biosynthesis and wounding response in the rubber tree. Identification of JAZ (jasmonate ZIM-domain) family of proteins that repress JA responses has facilitated rapid progress in understanding how this lipid-derived hormone controls gene expression and related physiological processes in plants. In this work, the full-length cDNAs of six JAZ genes were cloned from H. brasiliensis (termed HbJAZ). These HbJAZ have different lengths and sequence diversity, but all of them contain Jas and ZIM domains, and two of them contain an ERF-associated amphiphilic repression (EAR) motif in the N-terminal. Real-time RT-PCR analyses revealed that HbJAZ have different expression patterns and tissue specificity. Four HbJAZ were up-regulated, one was down-regulated, while two were less effected by rubber tapping treatment, suggesting that they might play distinct roles in the wounding response. A yeast two-hybrid assay revealed that HbJAZ proteins interact with each other to form homologous or heterogeneous dimer complexes, indicating that the HbJAZ proteins may expand their function through diverse JAZ-JAZ interactions. This work lays a foundation for identification of the JA signalling pathway and molecular mechanisms of latex biosynthesis in rubber trees.

Topics: Amino Acid Motifs; Amino Acid Sequence; Cloning, Molecular; Cyclopentanes; Dimerization; Disease Resistance; DNA, Complementary; Gene Expression; Gene Expression Regulation, Plant; Genes, Plant; Hevea; Latex; Molecular Sequence Data; Multigene Family; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Polymerase Chain Reaction; Signal Transduction; Two-Hybrid System Techniques

Heat shock proteins (HSPs) function as molecular chaperones and are essential for the maintenance and/or restoration of protein homeostasis. The genus Xanthomonas type III effector protein AvrBsT induces hypersensitive cell death in pepper (Capsicum annuum). Here, we report the identification of the pepper CaHSP70a as an AvrBsT-interacting protein. Bimolecular fluorescence complementation and coimmunoprecipitation assays confirm the specific interaction between CaHSP70a and AvrBsT in planta. The CaHSP70a peptide-binding domain is essential for its interaction with AvrBsT. Heat stress (37°C) and Xanthomonas campestris pv vesicatoria (Xcv) infection distinctly induce CaHSP70a in pepper leaves. Cytoplasmic CaHSP70a proteins significantly accumulate in pepper leaves to induce the hypersensitive cell death response by Xcv (avrBsT) infection. Transient CaHSP70a overexpression induces hypersensitive cell death under heat stress, which is accompanied by strong induction of defense- and cell death-related genes. The CaHSP70a peptide-binding domain and ATPase-binding domain are required to trigger cell death under heat stress. Transient coexpression of CaHSP70a and avrBsT leads to cytoplasmic localization of the CaHSP70a-AvrBsT complex and significantly enhances avrBsT-triggered cell death in Nicotiana benthamiana. CaHSP70a silencing in pepper enhances Xcv growth but disrupts the reactive oxygen species burst and cell death response during Xcv infection. Expression of some defense marker genes is significantly reduced in CaHSP70a-silenced leaves, with lower levels of the defense hormones salicylic acid and jasmonic acid. Together, these results suggest that CaHSP70a interacts with the type III effector AvrBsT and is required for cell death and immunity in plants.

Topics: Bacterial Proteins; Bacterial Secretion Systems; Capsicum; Cell Death; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Gene Silencing; Genes, Plant; Heat-Shock Response; HSP70 Heat-Shock Proteins; Oxylipins; Plant Cells; Plant Diseases; Plant Immunity; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Protein Binding; Protein Structure, Tertiary; Reactive Oxygen Species; Salicylic Acid; Sequence Deletion; Subcellular Fractions; Two-Hybrid System Techniques; Xanthomonas campestris

Ethylene response factors (ERFs) comprise a large family of transcription factors that regulate numerous biological processes including growth, development, and response to environmental stresses. Here, we report that Pti5, an ERF in tomato [Solanum lycopersicum (Linnaeus)] was transcriptionally upregulated in response to the potato aphid Macrosiphum euphorbiae (Thomas), and contributed to plant defences that limited the population growth of this phloem-feeding insect. Virus-induced gene silencing of Pti5 enhanced aphid population growth on tomato, both on an aphid-susceptible cultivar and on a near-isogenic genotype that carried the Mi-1.2 resistance (R) gene. These results indicate that Pti5 contributes to basal resistance in susceptible plants and also can synergize with other R gene-mediated defences to limit aphid survival and reproduction. Although Pti5 contains the ERF motif, induction of this gene by aphids was independent of ethylene, since the ACC deaminase (ACD) transgene, which inhibits ethylene synthesis, did not diminish the responsiveness of Pti5 to aphid infestation. Furthermore, experiments with inhibitors of ethylene synthesis revealed that Pti5 and ethylene have distinctly different roles in plant responses to aphids. Whereas Pti5 contributed to antibiotic plant defences that limited aphid survival and reproduction on both resistant (Mi-1.2+) and susceptible (Mi-1.2-) genotypes, ethylene signalling promoted aphid infestation on susceptible plants but contributed to antixenotic defences that deterred the early stages of aphid host selection on resistant plants. These findings suggest that the antixenotic defences that inhibit aphid settling and the antibiotic defences that depress fecundity and promote mortality are regulated through different signalling pathways.

Topics: Animals; Antibiosis; Aphids; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Genotype; Host-Parasite Interactions; Models, Biological; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Solanum tuberosum

Plant mitogen-activated protein kinases (MPKs) transduce signals required for the induction of immunity triggered by host recognition of pathogen-associated molecular patterns. We isolated a full-length cDNA of a group B MPK (PgMPK4) from pearl millet. Autophosphorylation assay of recombinant PgMPK4 produced in Escherichia coli confirmed it as a kinase. Differential accumulation of PgMPK4 mRNA and kinase activity was observed between pearl millet cultivars 852B and IP18292 in response to inoculation with the downy mildew oomycete pathogen Sclerospora graminicola. This increased accumulation of PgMPK4 mRNA, kinase activity as well as nuclear-localization of PgMPK protein(s) was only detected in the S. graminicola resistant cultivar IP18292 with a ~tenfold peak at 9 h post inoculation. In the susceptible cultivar 852B, PgMPK4 mRNA and immuno-detectable nuclear PgMPK could be induced by application of the chemical elicitor β-amino butyric acid, the non-pathogenic bacteria Pseudomonas fluorescens, or by the phytohormones jasmonic acid (JA) or salicylic acid (SA). Furthermore, kinase inhibitor treatments indicated that PgMPK4 is involved in the JA- and SA-mediated expression of three defense genes, lipoxygenase, catalase 3 and polygalacturonase-inhibitor protein. These findings indicate that PgMPK/s contribute to pearl millet defense against the downy mildew pathogen by activating the expression of defense proteins.

Topics: Amino Acid Sequence; Base Sequence; Cloning, Molecular; Cyclopentanes; Disease Resistance; DNA, Plant; Genes, Plant; Mitogen-Activated Protein Kinases; Molecular Sequence Data; Oomycetes; Oxylipins; Pennisetum; Phylogeny; Plant Diseases; Plant Proteins; Recombinant Proteins; RNA, Messenger; RNA, Plant; Salicylic Acid; Sequence Homology, Amino Acid

Resistance of tomato (Solanum Lycopersicum) to the fungal pathogen Botrytis cinerea requires complex interplay between hormonal signalling. In this study, we explored the involvement of new oxylipins in the tomato basal and induced response to this necrotroph through the functional analysis of the tomato α-dioxygenase2 (α-DOX2)-deficient mutant divaricata. We also investigated the role of SA in the defence response against this necrotrophic fungus using SA-deficient tomato nahG plants. The plants lacking dioxigenase α-DOX2, which catalyses oxylipins production from fatty acids, were more susceptible to Botrytis, and hexanoic acid-induced resistance (Hx-IR) was impaired; hence α-DOX2 is required for both tomato defence and the enhanced protection conferred by natural inducer hexanoic acid (Hx) against B. cinerea. The divaricata plants accumulated less pathogen-induced callose and presented lower levels of jasmonic acid (JA) and 12-oxo-phytodienoic acid (OPDA) upon infection if compared to the wild type. Glutathion-S-transferase (GST) gene expression decreased and ROS production significantly increased in Botrytis-infected divaricata plants. These results indicate that absence of α-DOX2 influences the hormonal changes, oxidative burst and callose deposition that occur upon Botrytis infection in tomato. The study of SA-deficient nahG tomato plants showed that the plants with low SA levels displayed increased resistance to Botrytis, but were unable to display Hx-IR. This supports the involvement of SA in Hx-IR. NaghG plants displayed reduced callose and ROS accumulation upon infection and an increased GST expression. This reflects a positive relationship between SA and these defensive mechanisms in tomato. Finally, Hx boosted the pathogen-induced callose in nahG plants, suggesting that this priming mechanism is SA-independent. Our results support the involvement of the oxylipins pathway and SA in tomato response to Botrytis, probably through complex crosstalk of the hormonal balance with callose and ROS accumulation, and reinforce the role of the oxidative stress in the outcome of the plant-Botrytis interaction.

Topics: Botrytis; Caproates; Cyclopentanes; Dioxygenases; Disease Resistance; Fatty Acids, Unsaturated; Gene Expression Regulation, Plant; Glucans; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Reactive Oxygen Species; Salicylic Acid; Solanum lycopersicum

Housaku Monogatari (HM) is a plant activator prepared from a yeast cell wall extract. We examined the efficacy of HM application and observed that HM treatment increased the resistance of Arabidopsis thaliana and Brassica rapa leaves to bacterial and fungal infections. HM reduced the severity of bacterial leaf spot and anthracnose on A. thaliana and Brassica crop leaves with protective effects. In addition, gene expression analysis of A. thaliana plants after treatment with HM indicated increased expression of several plant defense-related genes. HM treatment appears to induce early activation of jasmonate/ethylene and late activation of salicylic acid (SA) pathways. Analysis using signaling mutants revealed that HM required SA accumulation and SA signaling to facilitate resistance to the bacterial pathogen Pseudomonas syringae pv. maculicola and the fungal pathogen Colletotrichum higginsianum. In addition, HM-induced resistance conferred chitin-independent disease resistance to bacterial pathogens in A. thaliana. These results suggest that HM contains multiple microbe-associated molecular patterns that activate defense responses in plants. These findings suggest that the application of HM is a useful tool that may facilitate new disease control methods.

Topics: Arabidopsis; Arabidopsis Proteins; Brassica; Cell Wall; Chitinases; Colletotrichum; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Pseudomonas syringae; Salicylic Acid; Signal Transduction; Yeasts

Blast caused by fungal Magnaporthe oryzae is a devastating disease of rice (Oryza sativa) worldwide, and this fungus also infects barley (Hordeum vulgare). At least 11 rice WRKY transcription factors have been reported to regulate rice response to M. oryzae either positively or negatively. However, the relationships of these WRKYs in the rice defense signaling pathway against M. oryzae are unknown. Previous studies have revealed that rice WRKY13 (as a transcriptional repressor) and WRKY45-2 enhance resistance to M. oryzae. Here, we show that rice WRKY42, functioning as a transcriptional repressor, suppresses resistance to M. oryzae. WRKY42-RNA interference (RNAi) and WRKY42-overexpressing (oe) plants showed increased resistance and susceptibility to M. oryzae, accompanied by increased or reduced jasmonic acid (JA) content, respectively, compared with wild-type plants. JA pretreatment enhanced the resistance of WRKY42-oe plants to M. oryzae. WRKY13 directly suppressed WRKY42. WRKY45-2, functioning as a transcriptional activator, directly activated WRKY13. In addition, WRKY13 directly suppressed WRKY45-2 by feedback regulation. The WRKY13-RNAi WRKY45-2-oe and WRKY13-oe WRKY42-oe double transgenic lines showed increased susceptibility to M. oryzae compared with WRKY45-2-oe and WRKY13-oe plants, respectively. These results suggest that the three WRKYs form a sequential transcriptional regulatory cascade. WRKY42 may negatively regulate rice response to M. oryzae by suppressing JA signaling-related genes, and WRKY45-2 transcriptionally activates WRKY13, whose encoding protein in turn transcriptionally suppresses WRKY42 to regulate rice resistance to M. oryzae.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Magnaporthe; Models, Biological; Molecular Sequence Data; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Promoter Regions, Genetic; Protein Binding; Repressor Proteins; Signal Transduction; Transcription Factors; Transcription, Genetic; Xanthomonas

Induced defenses play a key role in plant resistance against leaf feeders. However, very little is known about the signals that are involved in defending plants against root feeders and how they are influenced by abiotic factors. We investigated these aspects for the interaction between rice (Oryza sativa) and two root-feeding insects: the generalist cucumber beetle (Diabrotica balteata) and the more specialized rice water weevil (Lissorhoptrus oryzophilus). Rice plants responded to root attack by increasing the production of jasmonic acid (JA) and abscisic acid, whereas in contrast to in herbivore-attacked leaves, salicylic acid and ethylene levels remained unchanged. The JA response was decoupled from flooding and remained constant over different soil moisture levels. Exogenous application of methyl JA to the roots markedly decreased the performance of both root herbivores, whereas abscisic acid and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid did not have any effect. JA-deficient antisense 13-lipoxygenase (asLOX) and mutant allene oxide cyclase hebiba plants lost more root biomass under attack from both root herbivores. Surprisingly, herbivore weight gain was decreased markedly in asLOX but not hebiba mutant plants, despite the higher root biomass removal. This effect was correlated with a herbivore-induced reduction of sucrose pools in asLOX roots. Taken together, our experiments show that jasmonates are induced signals that protect rice roots from herbivores under varying abiotic conditions and that boosting jasmonate responses can strongly enhance rice resistance against root pests. Furthermore, we show that a rice 13-lipoxygenase regulates root primary metabolites and specifically improves root herbivore growth.

Topics: Animals; Biomass; Coleoptera; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Herbivory; Oryza; Oxylipins; Plant Proteins; Plant Roots; Real-Time Polymerase Chain Reaction; Signal Transduction; Sucrose; Water

Cotyledon wounding in pepper caused the early generation of hydrogen peroxide both locally (cotyledons) and systemically (upper true leaves). However, 72 h later there is a different wound response between local and systemic organs, as shown by resistance to the pathogenic fungus Botrytis cinerea, that increased locally and decreased systemically. Signaling by ethylene and jasmonic acid was assessed by using two inhibitors: 1-methylcyclopropene (MCP, inhibitor of ethylene receptors) and ibuprofen (inhibitor of jasmonate biosynthesis). MCP did not affect the modulation of resistance levels to Botrytis by wounding, ruling out the involvement of ethylene signaling. Ibuprofen did not inhibit wound-induced resistance at the local level, but inhibited wound-induced systemic susceptibility. Moreover, changes of biochemical and structural defenses in response to wounding were studied. Peroxidase activity and the expression of a peroxidase gene (CAPO1) increased locally as a response to wounding, but no changes were observed systemically. Lignin deposition was induced in wounded cotyledons, but was repressed in systemic leaves of wounded plants, whereas soluble phenolics did not change locally and decreased systemically. The expression of two other genes involved in plant defense (CABPR1 and CASC1) was also differentially regulated locally and systemically, pointing to a generalized increase in plant defenses at the local level and a systemic decrease as a response to wounding. Wound-induced defenses at the local level coincided with resistance to the necrotroph fungus B. cinerea, whereas depleted defenses in systemic leaves of wounded plants correlated to induced susceptibility against this pathogen. It may be that the local response acts as a sink of energy resources to mount a defense against pathogens, whereas in systemic organs the resources for defense are lower.

Topics: Botrytis; Capsicum; Chitinases; Cotyledon; Cyclopentanes; Cyclopropanes; Disease Resistance; Disease Susceptibility; Ethylenes; Gene Expression Regulation, Plant; Hydrogen Peroxide; Ibuprofen; Lignin; Oxylipins; Peroxidase; Phenols; Plant Diseases; Solubility

Specific wavelengths of light can exert various physiological changes in plants, including effects on responses to disease incidence. To determine whether specific light wavelength had effects on rotting disease caused by Pseudomonas putida 229, soybean sprouts were germinated under a narrow range of wavelengths from light emitting diodes (LEDs), including red (650-660), far red (720-730) and blue (440-450 nm) or broad range of wavelength from daylight fluorescence bulbs. The controls were composed of soybean sprouts germinated in darkness. After germination under different conditions for 5 days, the soybean sprouts were inoculated with P. putida 229 and the disease incidence was observed for 5 days. The sprouts exposed to red light showed increased resistance against P. putida 229 relative to those grown under other conditions. Soybean sprouts germinated under red light accumulated high levels of salicylic acid (SA) accompanied with up-regulation of the biosynthetic gene ICS and the pathogenesis- related (PR) gene PR-1, indicating that the resistance was induced by the action of SA via de novo synthesis of SA in the soybean sprouts by red light irradiation. Taken together, these data suggest that only the narrow range of red light can induce disease resistance in soybean sprouts, regulated by the SA-dependent pathway via the de novo synthesis of SA and up-regulation of PR genes.

Topics: Biosynthetic Pathways; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Germination; Glycine max; Light; Oxylipins; Plant Diseases; Salicylic Acid

Lipid transfer proteins (LTPs) are members of the family of pathogenesis-related proteins (PR-14) that are believed to be involved in plant defense responses. In this study, we report the isolation and characterization of a novel gene TdLTP4 encoding an LTP protein from durum wheat [Triticum turgidum L. subsp. Durum Desf.]. Molecular Phylogeny analyses of wheat TdLTP4 gene showed a high identity to other plant LTPs. Predicted three-dimensional structural model revealed the presence of six helices and nine loop turns. Expression analysis in two local durum wheat varieties with marked differences in salt and drought tolerance, revealed a higher transcript accumulation of TdLTP4 under different stress conditions in the tolerant variety, compared to the sensitive one. The overexpression of TdLTP4 in Arabidopsis resulted in a promoted plant growth under various stress conditions including NaCl, ABA, JA and H2O2 treatments. Moreover, the LTP-overexpressing lines exhibit less sensitivity to jasmonate than wild-type plants. Furthermore, detached leaves from transgenic Arabidopsis expressing TdLTP4 gene showed enhanced fungal resistance against Alternaria solani and Botrytis cinerea. Together, these data provide the evidence for the involvement of TdLTP4 gene in the tolerance to both abiotic and biotic stresses in crop plants.

Topics: Abscisic Acid; Adaptation, Physiological; Antigens, Plant; Arabidopsis; Carrier Proteins; Cyclopentanes; Disease Resistance; Droughts; Fungi; Genes, Plant; Hydrogen Peroxide; Models, Molecular; Molecular Structure; Oxylipins; Phylogeny; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Salt Tolerance; Sodium Chloride; Stress, Physiological; Transcription, Genetic; Triticum

Jasmonates regulate plant secondary metabolism and herbivore resistance. How they influence primary metabolites and how this may affect herbivore growth and performance are not well understood. We profiled sugars and starch of jasmonate biosynthesis-deficient and jasmonate-insensitive Nicotiana attenuata plants and manipulated leaf carbohydrates through genetic engineering and in vitro complementation to assess how jasmonate-dependent sugar accumulation affects the growth of Manduca sexta caterpillars. We found that jasmonates reduce the constitutive and herbivore-induced concentration of glucose and fructose in the leaves across different developmental stages. Diurnal, jasmonate-dependent inhibition of invertase activity was identified as a likely mechanism for this phenomenon. Contrary to our expectation, both in planta and in vitro approaches showed that the lower sugar concentrations led to increased M. sexta growth. As a consequence, jasmonate-dependent depletion of sugars rendered N. attenuata plants more susceptible to M. sexta attack. In conclusion, jasmonates are important regulators of leaf carbohydrate accumulation and this determines herbivore growth. Jasmonate-dependent resistance is reduced rather than enhanced through the suppression of glucose and fructose concentrations, which may contribute to the evolution of divergent resistance strategies of plants in nature.

Topics: Animals; beta-Fructofuranosidase; Carbohydrates; Circadian Rhythm; Cyclopentanes; Disease Resistance; Fructose; Genotype; Glucose; Herbivory; Manduca; Nicotiana; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Ribulose-Bisphosphate Carboxylase; Secondary Metabolism; Signal Transduction; Solubility; Weight Gain

Phytohormones play an important role in development and stress adaptations in plants, and several interacting hormonal pathways have been suggested to accomplish fine-tuning of stress responses at the expense of growth. This work describes the role played by the CALCIUM-DEPENDENT PROTEIN KINASE CPK28 in balancing phytohormone-mediated development in Arabidopsis thaliana, specifically during generative growth. cpk28 mutants exhibit growth reduction solely as adult plants, coinciding with altered balance of the phytohormones jasmonic acid (JA) and gibberellic acid (GA). JA-dependent gene expression and the levels of several JA metabolites were elevated in a growth phase-dependent manner in cpk28, and accumulation of JA metabolites was confined locally to the central rosette tissue. No elevated resistance toward herbivores or necrotrophic pathogens was detected for cpk28 plants, either on the whole-plant level or specifically within the tissue displaying elevated JA levels. Abolishment of JA biosynthesis or JA signaling led to a full reversion of the cpk28 growth phenotype, while modification of GA signaling did not. Our data identify CPK28 as a growth phase-dependent key negative regulator of distinct processes: While in seedlings, CPK28 regulates reactive oxygen species-mediated defense signaling; in adult plants, CPK28 confers developmental processes by the tissue-specific balance of JA and GA without affecting JA-mediated defense responses.

Topics: Animals; Arabidopsis; Calcium; Cyclopentanes; Disease Resistance; Environment; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant; Gibberellins; Metabolome; Mutation; Organ Specificity; Oxylipins; Phenotype; Protein Kinases; Reactive Oxygen Species; Signal Transduction; Spodoptera

The citrus rootstocks sour orange and Cleopatra mandarin display differential resistance against Tetranychus urticae. Sour orange plants support reduced oviposition, growth rates and damage compared with Cleopatra mandarin plants. Jasmonic acid signalling and flavonoid accumulation have been revealed as key mechanisms for the enhanced resistance of sour orange plants. In this study, we observed that the release of T. urticae herbivore-induced plant volatiles (HIPVs) from sour orange plants has a marked repellent effect on conspecific mites associated with the production of the terpenes α-ocimene, α-farnesene, pinene and d-limonene, and the green leaf volatile 4-hydroxy-4-methyl-2-pentanone. By contrast, T. urticae HIPVs from Cleopatra mandarin plants promote conspecific mite attraction associated with an increase in (2-butoxyethoxy) ethanol, benzaldehyde and methyl salicylate levels. HIPVs released from sour orange plants following T. urticae infestation induce resistance in Cleopatra mandarin plants, thereby reducing oviposition rates and stimulating the oxylipin biosynthetic gene lipoxygenase2 (LOX2). Cleopatra HIPVs do not affect the response to T. urticae of these rootstocks. We conclude that sour orange plants promote herbivore-induced resistance in Cleopatra mandarin plants and, despite the weak basal resistance of these rootstocks, herbivore resistance can be induced through the combination of HIPVs, such as α-ocimene and d-limonene.

Topics: Animals; Chromatography, High Pressure Liquid; Citrus; Cyclopentanes; Disease Resistance; Fatty Acids, Unsaturated; Gene Expression Regulation, Plant; Genotype; Herbivory; Insect Repellents; Metabolomics; Oxylipins; Plant Diseases; Plant Proteins; Salicylic Acid; Smell; Tetranychidae; Volatilization

PR genes, a type of genetic marker, are constitutively expressed at background levels, while being easily inducible by pathogenic bacteria. By using a yeast two-hybrid technique, four rice (Oryza sativa L.) OsPR1b-interacting factors were screened. Homozygous plants overexpressing OsPR1b were prepared by transgenic technology. We postulated that OsPR1b may participate in the resistance signaling pathway of rice. Of simultaneous treatments with hormones and pathogenic bacteria, exogenously applying JA and ET significantly increased the expression level of OsPR1b genes in seedlings. Compared with the control group that was inoculated with water, inoculation with a mixture of water and pathogenic bacteria hardly affected the expression level of OsPR1b gene, while cotreatment with SA and pathogenic bacteria slightly upregulated the expression level. However, cotreatment with JA or ET and pathogenic bacteria managed to significantly upregulate the expression level of the OsPR1b gene by 4.8 or 5.7 fold. PR genes, which are sensitive, are prone to many unknown factors during expression, and the detailed regulatory mechanisms in rice still require in-depth studies.

Topics: Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Breeding; Plant Diseases; Plant Proteins; Seedlings; Two-Hybrid System Techniques; Up-Regulation; Xanthomonas

High temperature (HT), high humidity (HH), and pathogen infection often co-occur and negatively affect plant growth. However, these stress factors and plant responses are generally studied in isolation. The mechanisms of synergistic responses to combined stresses are poorly understood. We isolated the subgroup IIb WRKY family member CaWRKY6 from Capsicum annuum and performed quantitative real-time PCR analysis. CaWRKY6 expression was upregulated by individual or simultaneous treatment with HT, HH, combined HT and HH (HTHH), and Ralstonia solanacearum inoculation, and responded to exogenous application of jasmonic acid (JA), ethephon, and abscisic acid (ABA). Virus-induced gene silencing of CaWRKY6 enhanced pepper plant susceptibility to R. solanacearum and HTHH, and downregulated the hypersensitive response (HR), JA-, ethylene (ET)-, and ABA-induced marker gene expression, and thermotolerance-associated expression of CaHSP24, ER-small CaSHP, and Chl-small CaHSP. CaWRKY6 overexpression in pepper attenuated the HTHH-induced suppression of resistance to R. solanacearum infection. CaWRKY6 bound to and activated the CaWRKY40 promoter in planta, which is a pepper WRKY that regulates heat-stress tolerance and R. solanacearum resistance. CaWRKY40 silencing significantly blocked HR-induced cell death and reduced transcriptional expression of CaWRKY40. These data suggest that CaWRKY6 is a positive regulator of R. solanacearum resistance and heat-stress tolerance, which occurs in part by activating CaWRKY40.

Topics: Abscisic Acid; Base Sequence; Capsicum; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Hot Temperature; Humidity; Molecular Sequence Data; Organophosphorus Compounds; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Ralstonia solanacearum; Sequence Analysis, DNA; Stress, Physiological; Transcription Factors

Induced resistance to the necrotrophic pathogen Botrytis cinerea depends on jasmonate metabolism and signalling in Arabidopsis. We have presented here extensive jasmonate profiling in this pathosystem and investigated the impact of the recently reported jasmonoyl-isoleucine (JA-Ile) catabolic pathway mediated by cytochrome P450 (CYP94) enzymes. Using a series of mutant and overexpressing (OE) plant lines, we showed that CYP94B3 and CYP94C1 are integral components of the fungus-induced jasmonate metabolic pathway and control the abundance of oxidized conjugated but also some unconjugated derivatives, such as sulfated 12-HSO4-JA. Despite causing JA-Ile overaccumulation due to impaired oxidation, CYP94 deficiency had negligible impacts on resistance, associated with enhanced JAZ repressor transcript levels. In contrast, plants overexpressing (OE) CYP94B3 or CYP94C1 were enriched in 12-OH-JA-Ile or 12-COOH-JA-Ile respectively. This shift towards oxidized JA-Ile derivatives was concomitant with strongly impaired defence gene induction and reduced disease resistance. CYP94B3-OE, but unexpectedly not CYP94C1-OE, plants displayed reduced JA-Ile levels compared with the wild type, suggesting that increased susceptibility in CYP94C1-OE plants may result from changes in the hormone oxidation ratio rather than absolute changes in JA-Ile levels. Consistently, while feeding JA-Ile to seedlings triggered strong induction of JA pathway genes, induction was largely reduced or abolished after feeding with the CYP94 products 12-OH-JA-Ile and 12-COOH-JA-Ile, respectively. This trend paralleled in vitro pull-down assays where 12-COOH-JA-Ile was unable to promote COI1-JAZ9 co-receptor assembly. Our results highlight the dual function of CYP94B3/C1 in antimicrobial defence: by controlling hormone oxidation status for signal attenuation, these enzymes also define JA-Ile as a metabolic hub directing jasmonate profile complexity.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Cytochrome P-450 Enzyme System; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Isoleucine; Metabolic Networks and Pathways; Models, Biological; Mutation; Oxidation-Reduction; Oxylipins; Plant Diseases; Salicylic Acid

Glutathione S-transferases (GSTs) play important roles in the protection of cells against toxins and oxidative damage where one Arabidopsis member, GSTF8, has become a commonly used marker gene for early stress and defense responses. A GSTF8 promoter fragment fused to the luciferase reporter gene was used in a forward genetic screen for Arabidopsis mutants with up-regulated GSTF8 promoter activity. This identified the esr1-1 (enhanced stress response 1) mutant which also conferred increased resistance to the fungal pathogen Fusarium oxysporum. Through positional cloning, the ESR1 gene was found to encode a KH-domain containing RNA-binding protein (At5g53060). Whole transcriptome sequencing of esr1-1 identified altered expression of genes involved in responses to biotic and abiotic stimuli, hormone signaling pathways and developmental processes. In particular was an overall significant enrichment for jasmonic acid (JA) mediated processes in the esr1-1 down-regulated dataset. A subset of these genes were tested for MeJA inducibility and we found the expression of some but not all were reduced in esr1-1. The esr1-1 mutant was not impaired in other aspects of JA-signalling such as JA- sensitivity or development, suggesting ESR1 functions in specific components of the JA-signaling pathway. Examination of salicylic acid (SA) regulated marker genes in esr1-1 showed no increase in basal or SA induced expression suggesting repression of JA-regulated genes is not due to antagonistic SA-JA crosstalk. These results define new roles for KH-domain containing proteins with ESR1 unlinking JA-mediated growth and defense responses.

Topics: Adaptation, Physiological; Alleles; Arabidopsis; Arabidopsis Proteins; Cloning, Molecular; Cyclopentanes; Disease Resistance; Down-Regulation; Fusarium; Gene Expression Regulation, Plant; Gene Ontology; Glutathione Transferase; Mutation; Oxylipins; Plant Diseases; Protein Structure, Tertiary; Recombinant Fusion Proteins; RNA-Binding Proteins; Salicylic Acid; Sequence Analysis, RNA; Signal Transduction; Stress, Physiological; Transcription Factors; Transcriptome; Up-Regulation

The root hemiparasite witchweed (Striga spp.) is a devastating agricultural pest that causes losses of up to $1 billion US annually in sub-Saharan Africa. Development of resistant crops is one of the cost-effective ways to address this problem. However, the molecular mechanisms underlying resistance are not well understood. To understand molecular events upon Striga spp. infection, we conducted genome-scale RNA sequencing expression analysis using Striga hermonthica-infected rice (Oryza sativa) roots. We found that transcripts grouped under the Gene Ontology term defense response were significantly enriched in up-regulated differentially expressed genes. In particular, we found that both jasmonic acid (JA) and salicylic acid (SA) pathways were induced, but the induction of the JA pathway preceded that of the SA pathway. Foliar application of JA resulted in higher resistance. The hebiba mutant plants, which lack the JA biosynthesis gene allene oxide cyclase, exhibited severe S. hermonthica susceptibility. The resistant phenotype was recovered by application of JA. By contrast, the SA-deficient NahG rice plants were resistant against S. hermonthica, indicating that endogenous SA is not required for resistance. However, knocking down WRKY45, a regulator of the SA/benzothiadiazole pathway, resulted in enhanced susceptibility. Interestingly, NahG plants induced the JA pathway, which was down-regulated in WRKY45-knockdown plants, linking the resistant and susceptible phenotypes to the JA pathway. Consistently, the susceptibility phenotype in the WRKY45-knockdown plants was recovered by foliar JA application. These results point to a model in which WRKY45 modulates a cross talk in resistance against S. hermonthica by positively regulating both SA/benzothiadiazole and JA pathways.

Topics: Cyclopentanes; Disease Resistance; Down-Regulation; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Models, Biological; Mutation; Oryza; Oxylipins; Plant Diseases; Plant Proteins; RNA, Messenger; Salicylic Acid; Signal Transduction; Striga; Thiadiazoles

The ERF (ethylene responsive factor) family is composed of transcription factors (TFs) that are critical for appropriate Arabidopsis thaliana responses to biotic and abiotic stresses. Here we identified and characterized a member of the ERF TF group IX, namely ERF96, that when overexpressed enhances Arabidopsis resistance to necrotrophic pathogens such as the fungus Botrytis cinerea and the bacterium Pectobacterium carotovorum. ERF96 is jasmonate (JA) and ethylene (ET) responsive and ERF96 transcripts accumulation was abolished in JA-insensitive coi1-16 and in ET-insensitive ein2-1 mutants. Protoplast transactivation and electrophoresis mobility shift analyses revealed that ERF96 is an activator of transcription that binds to GCC elements. In addition, ERF96 mainly localized to the nucleus. Microarray analysis coupled to chromatin immunoprecipitation-PCR of Arabidopsis overexpressing ERF96 revealed that ERF96 enhances the expression of the JA/ET defence genes PDF1.2a, PR-3 and PR-4 as well as the TF ORA59 by direct binding to GCC elements present in their promoters. While ERF96-RNAi plants demonstrated wild-type resistance to necrotrophic pathogens, basal PDF1.2 expression levels were reduced in ERF96-silenced plants. This work revealed ERF96 as a key player of the ERF network that positively regulates the Arabidopsis resistance response to necrotrophic pathogens.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Defensins; Disease Resistance; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Oligonucleotide Array Sequence Analysis; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plants, Genetically Modified; Promoter Regions, Genetic; Recombinant Proteins; Seedlings; Transcription Factors

Fusarium graminearum causes Fusarium head blight, an important disease of wheat. F. graminearum can also cause disease in Arabidopsis thaliana. Here, we show that the Arabidopsis LOX1 and LOX5 genes, which encode 9-lipoxygenases (9-LOXs), are targeted during this interaction to facilitate infection. LOX1 and LOX5 expression were upregulated in F. graminearum-inoculated plants and loss of LOX1 or LOX5 function resulted in enhanced disease resistance in the corresponding mutant plants. The enhanced resistance to F. graminearum infection in the lox1 and lox5 mutants was accompanied by more robust induction of salicylic acid (SA) accumulation and signaling and attenuation of jasmonic acid (JA) signaling in response to infection. The lox1- and lox5-conferred resistance was diminished in plants expressing the SA-degrading salicylate hydroxylase or by the application of methyl-JA. Results presented here suggest that plant 9-LOXs are engaged during infection to control the balance between SA and JA signaling to facilitate infection. Furthermore, since silencing of TaLpx-1 encoding a 9-LOX with homology to LOX1 and LOX5, resulted in enhanced resistance against F. graminearum in wheat, we suggest that 9-LOXs have a conserved role as susceptibility factors in disease caused by this important fungus in Arabidopsis and wheat.

Topics: Arabidopsis; Base Sequence; Cyclopentanes; Disease Resistance; Fusarium; Gene Knockdown Techniques; Genes, Reporter; Lipoxygenases; Molecular Sequence Data; Mutation; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Salicylic Acid; Sequence Analysis, DNA; Signal Transduction; Triticum

Although Sclerotinia sclerotiorum is a devastating necrotrophic fungal plant pathogen in agriculture, the virulence mechanisms utilized by S. sclerotiorum and the host defense mechanisms against this pathogen have not been fully understood. Here, we report that the Arabidopsis (Arabidopsis thaliana) Mediator complex subunit MED16 is a key component of basal resistance against S. sclerotiorum. Mutants of MED16 are markedly more susceptible to S. sclerotiorum than mutants of 13 other Mediator subunits, and med16 has a much stronger effect on S. sclerotiorum-induced transcriptome changes compared with med8, a mutation not altering susceptibility to S. sclerotiorum. Interestingly, med16 is also more susceptible to S. sclerotiorum than coronatine-insensitive1-1 (coi1-1), which is the most susceptible mutant reported so far. Although the jasmonic acid (JA)/ethylene (ET) defense pathway marker gene PLANT DEFENSIN1.2 (PDF1.2) cannot be induced in either med16 or coi1-1, basal transcript levels of PDF1.2 in med16 are significantly lower than in coi1-1. Furthermore, ET-induced suppression of JA-activated wound responses is compromised in med16, suggesting a role for MED16 in JA-ET cross talk. Additionally, MED16 is required for the recruitment of RNA polymerase II to PDF1.2 and OCTADECANOID-RESPONSIVE ARABIDOPSIS ETHYLENE/ETHYLENE-RESPONSIVE FACTOR59 (ORA59), two target genes of both JA/ET-mediated and the transcription factor WRKY33-activated defense pathways. Finally, MED16 is physically associated with WRKY33 in yeast and in planta, and WRKY33-activated transcription of PDF1.2 and ORA59 as well as resistance to S. sclerotiorum depends on MED16. Taken together, these results indicate that MED16 regulates resistance to S. sclerotiorum by governing both JA/ET-mediated and WRKY33-activated defense signaling in Arabidopsis.

Topics: Amino Acids, Cyclic; Arabidopsis; Arabidopsis Proteins; Ascomycota; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Mediator Complex; Oxylipins; Plant Diseases; Protein Binding; RNA Polymerase II; Signal Transduction; Trans-Activators; Transcription Factors; Transcription, Genetic; Transcriptome

Mature grapevine berries at the harvesting stage (MB) are very susceptible to the gray mold fungus Botrytis cinerea, while veraison berries (VB) are not. We conducted simultaneous microscopic and transcriptomic analyses of the pathogen and the host to investigate the infection process developed by B. cinerea on MB versus VB, and the plant defense mechanisms deployed to stop the fungus spreading. On the pathogen side, our genome-wide transcriptomic data revealed that B. cinerea genes upregulated during infection of MB are enriched in functional categories related to necrotrophy, such as degradation of the plant cell wall, proteolysis, membrane transport, reactive oxygen species (ROS) generation, and detoxification. Quantitative-polymerase chain reaction on a set of representative genes related to virulence and microscopic observations further demonstrated that the infection is also initiated on VB but is stopped at the penetration stage. On the plant side, genome-wide transcriptomic analysis and metabolic data revealed a defense pathway switch during berry ripening. In response to B. cinerea inoculation, VB activated a burst of ROS, the salicylate-dependent defense pathway, the synthesis of the resveratrol phytoalexin, and cell-wall strengthening. On the contrary, in infected MB, the jasmonate-dependent pathway was activated, which did not stop the fungal necrotrophic process.

Topics: Botrytis; Cell Wall; Cyclopentanes; Disease Resistance; Fruit; Gene Expression Profiling; Gene Expression Regulation, Developmental; Gene Expression Regulation, Fungal; Gene Expression Regulation, Plant; Gene Ontology; Host-Pathogen Interactions; Oligonucleotide Array Sequence Analysis; Oxylipins; Phytoalexins; Plant Diseases; Reactive Oxygen Species; Resveratrol; Reverse Transcriptase Polymerase Chain Reaction; Salicylates; Sesquiterpenes; Stilbenes; Virulence; Vitis

Platelet-activating factor acetylhydrolase (PAF-AH) derived from Trichoderma harzianum was upregulated by the interaction of T. harzianum with maize roots or the foliar pathogen Curvularia lunata. PAF-AH was associated with chitinase and cellulase expressions, but especially with chitinase, because its activity in the KO40 transformant (PAF-AH disruption transformant) was lower, compared with the wild-type strain T28. The result demonstrated that the colonization of maize roots by T. harzianum induced systemic protection of leaves inoculated with C. lunata. Such protection was associated with the expression of inducible jasmonic acid pathway-related genes. Moreover, the data from liquid chromatography-mass spectrometry confirmed that the concentration of jasmonic acid in maize leaves was associated with the expression level of defense-related genes, suggesting that PAF-AH induced resistance to the foliar pathogen. Our findings showed that PAF-AH had an important function in inducing systemic resistance to maize leaf spot pathogen.

Topics: Ascomycota; Chitinases; Cyclopentanes; Disease Resistance; Fungal Proteins; Gene Expression; Oxylipins; Plant Diseases; Plant Leaves; Plant Roots; Signal Transduction; Trichoderma; Zea mays

Feeding by insect herbivores activates plant signaling pathways, resulting in the enhanced production of secondary metabolites and other resistance-related traits by injured plants. These traits can reduce insect fitness, deter feeding, and attract beneficial insects. Organic and inorganic chemicals applied as a foliar spray, seed treatment, or soil drench can activate these plant responses. Azelaic acid (AA), benzothiadiazole (BTH), gibberellic acid (GA), harpin, and jasmonic acid (JA) are thought to directly mediate plant responses to pathogens and herbivores or to mimic compounds that do. The effects of these potential elicitors on the induction of plant defenses were determined by measuring the weight gains of fall armyworm, Spodoptera frugiperda (J. E. Smith) (FAW) (Lepidoptera: Noctuidae) larvae on four crop plants, cotton, corn, rice, and soybean, treated with the compounds under greenhouse conditions. Treatment with JA consistently reduced growth of FAW reared on treated cotton and soybean. In contrast, FAW fed BTH- and harpin-treated cotton and soybean tissue gained more weight than those fed control leaf tissue, consistent with negative crosstalk between the salicylic acid and JA signaling pathways. No induction or inconsistent induction of resistance was observed in corn and rice. Follow-up experiments showed that the co-application of adjuvants with JA failed to increase the effectiveness of induction by JA and that soybean looper [Chrysodeixis includens (Walker)], a relative specialist on legumes, was less affected by JA-induced responses in soybean than was the polyphagous FAW. Overall, the results of these experiments demonstrate that the effectiveness of elicitors as a management tactic will depend strongly on the identities of the crop, the pest, and the elicitor involved.

Topics: Animals; Crops, Agricultural; Cyclopentanes; Dicarboxylic Acids; Disease Resistance; Gibberellins; Glycine max; Gossypium; Herbivory; Oryza; Oxylipins; Spodoptera; Thiadiazoles; Zea mays

Arabidopsis VQ motif-containing proteins have recently been demonstrated to interact with several WRKY transcription factors; however, their specific biological functions and the molecular mechanisms underlying their involvement in defense responses remain largely unclear. Here, we showed that two VQ genes, VQ12 and VQ29, were highly responsive to the necrotrophic fungal pathogen Botrytis cinerea. To characterize their roles in plant defense, we generated amiR-vq12 transgenic plants by using an artificial miRNA approach to suppress the expression of VQ12, and isolated a loss-of-function mutant of VQ29. Phenotypic analysis showed that decreasing the expression of VQ12 and VQ29 simultaneously rendered the amiR-vq12 vq29 double mutant plants resistant against B. cinerea. Consistently, the B. cinerea-induced expression of defense-related PLANT DEFENSIN1.2 (PDF1.2) was increased in amiR-vq12 vq29. In contrast, constitutively-expressing VQ12 or VQ29 confered transgenic plants susceptible to B. cinerea. Further investigation revealed that VQ12 and VQ29 physically interacted with themselves and each other to form homodimers and heterodimer. Moreover, expression analysis of VQ12 and VQ29 in defense-signaling mutants suggested that they were partially involved in jasmonate (JA)-signaling pathway. Taken together, our study indicates that VQ12 and VQ29 negatively regulate plant basal resistance against B. cinerea.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Defensins; Disease Resistance; Green Fluorescent Proteins; Oxylipins; Plant Diseases; Plants, Genetically Modified; Promoter Regions, Genetic; Signal Transduction; Trans-Activators; Transcription Factors

The mechanisms by which herbivore-attacked plants activate their defenses are well studied. By contrast, little is known about the regulatory mechanisms that allow them to control their defensive investment and avoid a defensive overshoot. We characterized a rice (Oryza sativa) WRKY gene, OsWRKY53, whose expression is rapidly induced upon wounding and induced in a delayed fashion upon attack by the striped stem borer (SSB) Chilo suppressalis. The transcript levels of OsWRKY53 are independent of endogenous jasmonic acid but positively regulated by the mitogen-activated protein kinases OsMPK3/OsMPK6. OsWRKY53 physically interacts with OsMPK3/OsMPK6 and suppresses their activity in vitro. By consequence, it modulates the expression of defensive, MPK-regulated WRKYs and thereby reduces jasmonic acid, jasmonoyl-isoleucine, and ethylene induction. This phytohormonal reconfiguration is associated with a reduction in trypsin protease inhibitor activity and improved SSB performance. OsWRKY53 is also shown to be a negative regulator of plant growth. Taken together, these results show that OsWRKY53 functions as a negative feedback modulator of MPK3/MPK6 and thereby acts as an early suppressor of induced defenses. OsWRKY53 therefore enables rice plants to control the magnitude of their defensive investment during early signaling.

Topics: Amino Acid Sequence; Animals; Base Sequence; Cyclopentanes; Disease Resistance; Feedback, Physiological; Gene Expression Regulation, Plant; Herbivory; Host-Parasite Interactions; Immunoblotting; Mitogen-Activated Protein Kinases; Molecular Sequence Data; Moths; Oryza; Oxylipins; Phylogeny; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Protein Binding; Reverse Transcriptase Polymerase Chain Reaction; Transcription Factors; Two-Hybrid System Techniques

The circadian clock, an internal time-keeping mechanism, allows plants to anticipate regular changes in the environment, such as light and dark, and biotic challenges such as pathogens and herbivores. Here, we demonstrate that the plant circadian clock influences susceptibility to the necrotrophic fungal pathogen, Botrytis cinerea. Arabidopsis plants show differential susceptibility to B. cinerea depending on the time of day of inoculation. Decreased susceptibility after inoculation at dawn compared with night persists under constant light conditions and is disrupted in dysfunctional clock mutants, demonstrating the role of the plant clock in driving time-of-day susceptibility to B. cinerea. The decreased susceptibility to B. cinerea following inoculation at subjective dawn was associated with faster transcriptional reprogramming of the defence response with gating of infection-responsive genes apparent. Direct target genes of core clock regulators were enriched among the transcription factors that responded more rapidly to infection at subjective dawn than subjective night, suggesting an influence of the clock on the defence-signalling network. In addition, jasmonate signalling plays a crucial role in the rhythmic susceptibility of Arabidopsis to B. cinerea with the enhanced susceptibility to this pathogen at subjective night lost in a jaz6 mutant.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Circadian Clocks; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oxylipins; Repressor Proteins; Signal Transduction; Time Factors

Wild peanut relatives (Arachis spp.) are genetically diverse and were adapted to a range of environments during the evolution course, constituting an important source of allele diversity for resistance to biotic and abiotic stresses. The wild diploid A. stenosperma harbors high levels of resistance to a variety of pathogens, including the root-knot nematode (RKN) Meloidogyne arenaria, through the onset of the Hypersensitive Response (HR). In order to identify genes and regulators triggering this defense response, a comprehensive root transcriptome analysis during the first stages of this incompatible interaction was conducted using Illumina Hi-Seq. Overall, eight cDNA libraries were produced generating 28.2 GB, which were de novo assembled into 44,132 contigs and 37,882 loci. Differentially expressed genes (DEGs) were identified and clustered according to their expression profile, with the majority being downregulated at 6 DAI, which coincides with the onset of the HR. Amongst these DEGs, 27 were selected for further qRT-PCR validation allowing the identification of nematode-responsive candidate genes that are putatively related to the resistance response. Those candidates are engaged in the salycilic (NBS-LRR, lipocalins, resveratrol synthase) and jasmonic (patatin, allene oxidase cyclase) acids pathways, and also related to hormonal balance (auxin responsive protein, GH3) and cellular plasticity and signaling (tetraspanin, integrin, expansin), with some of them showing contrasting expression behavior between Arachis RKN-resistant and susceptible genotypes. As these candidate genes activate different defensive signaling systems, the genetic (HR) and the induced resistance (IR), their pyramidding in one genotype via molecular breeding or transgenic strategy might contribute to a more durable resistance, thus improving the long-term control of RKN in peanut.

Topics: Animals; Arachis; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Genes, Plant; Lipocalins; Oxylipins; Plant Diseases; Plant Roots; Resveratrol; Stilbenes; Tylenchoidea

Histone H2B monoubiquitination pathway has been shown to play critical roles in regulating growth/development and stress response in Arabidopsis. In the present study, we explored the involvement of the tomato histone H2B monoubiquitination pathway in defense response against Botrytis cinerea by functional analysis of SlHUB1 and SlHUB2, orthologues of the Arabidopsis AtHUB1/AtHUB2.. We used the TRV-based gene silencing system to knockdown the expression levels of SlHUB1 or SlHUB2 in tomato plants and compared the phenotype between the silenced and the control plants after infection with B. cinerea and Pseudomonas syringae pv. tomato (Pst) DC3000. Biochemical and interaction properties of proteins were examined using in vitro histone monoubiquitination and yeast two-hybrid assays, respectively. The transcript levels of genes were analyzed by quantitative real time PCR (qRT-PCR).. The tomato SlHUB1 and SlHUB2 had H2B monoubiquitination E3 ligases activity in vitro and expression of SlHUB1 and SlHUB2 was induced by infection of B. cinerea and Pst DC3000 and by treatment with salicylic acid (SA) and 1-amino cyclopropane-1-carboxylic acid (ACC). Silencing of either SlHUB1 or SlHUB2 in tomato plants showed increased susceptibility to B. cinerea, whereas silencing of SlHUB1 resulted in increased resistance against Pst DC3000. SlMED21, a Mediator complex subunit, interacted with SlHUB1 but silencing of SlMED21 did not affect the disease resistance to B. cinerea and Pst DC3000. The SlHUB1- and SlHUB2-silenced plants had thinner cell wall but increased accumulation of reactive oxygen species (ROS), increased callose deposition and exhibited altered expression of the genes involved in phenylpropanoid pathway and in ROS generation and scavenging system. Expression of genes in the SA-mediated signaling pathway was significantly upregulated, whereas expression of genes in the jasmonic acid (JA)/ethylene (ET)-mediated signaling pathway were markedly decreased in SlHUB1- and SlHUB2-silenced plants after infection of B. cinerea.. VIGS-based functional analyses demonstrate that both SlHUB1 and SlHUB2 contribute to resistance against B. cinerea most likely through modulating the balance between the SA- and JA/ET-mediated signaling pathways.

Topics: Amino Acid Sequence; Botrytis; Cell Wall; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Gene Silencing; Histones; Molecular Sequence Data; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Propanols; Protein Binding; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Ubiquitin-Protein Ligases; Ubiquitination

Corn defense systems against insect herbivory involve activation of genes that lead to metabolic reconfigurations to produce toxic compounds, proteinase inhibitors, oxidative enzymes, and behavior-modifying volatiles. Similar responses occur when the plant is exposed to methyl jasmonate (MeJA). To compare the defense responses between stalk borer feeding and exogenous MeJA on a transcriptional level, we employed deep transcriptome sequencing methods following Ostrinia furnacalis leaf feeding and MeJA leaf treatment. 39,636 genes were found to be differentially expressed with O. furnacalis feeding, MeJA application, and O. furnacalis feeding and MeJA application. Following Gene Ontology enrichment analysis of the up- or down- regulated genes, many were implicated in metabolic processes, stimuli-responsive catalytic activity, and transfer activity. Fifteen genes that indicated significant changes in the O. furnacalis feeding group: LOX1, ASN1, eIF3, DXS, AOS, TIM, LOX5, BBTI2, BBTI11, BBTI12, BBTI13, Cl-1B, TPS10, DOX, and A20/AN1 were found to almost all be involved in jasmonate defense signaling pathways. All of the data demonstrate that the jasmonate defense signal pathway is a major defense signaling pathways of Asian corn borer's defense against insect herbivory. The transcriptome data are publically available at NCBI SRA: SRS965087.

Topics: Alternative Splicing; Animals; Cluster Analysis; Computational Biology; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; High-Throughput Nucleotide Sequencing; Host-Parasite Interactions; Insecta; Oxylipins; Plant Leaves; Polymorphism, Single Nucleotide; Reproducibility of Results; Signal Transduction; Transcriptome; Zea mays

AsES (Acremonium strictum Elicitor and Subtilisin) is a novel extracellular elicitor protein produced by the avirulent isolate SS71 of the opportunist strawberry fungal pathogen A. strictum. Here we describe the activity of AsES in the plant-pathogen system Arabidopsis thaliana-Botrytis cinerea. We show that AsES renders A. thaliana plants resistant to the necrotrophic pathogen B. cinerea, both locally and systemically and the defense response observed is dose-dependent. Systemic, but not local resistance is dependent on the length of exposure to AsES. The germination of the spores in vitro was not inhibited by AsES, implying that protection to B. cinerea is due to the induction of the plant defenses. These results were further supported by the findings that AsES differentially affects mutants impaired in the response to salicylic acid, jasmonic acid and ethylene, suggesting that AsES triggers the defense response through these three signaling pathways.

Topics: Acremonium; Arabidopsis; Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Fungal Proteins; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Salicylic Acid; Signal Transduction

Plants have developed an efficient system of recognition that induces a complex network of signalling molecules such as salicylic acid (SA), jasmonic acid (JA) and abscisic acid (ABA) in case of a pathogenic infection. The use of specific and sensitive methods is mandatory for the analysis of compounds in these complex samples.. In this study a liquid chromatography/electrospray ionisation tandem mass spectrometry method was developed and validated for the simultaneous quantification of SA, JA and ABA in Coffea arabica (L.) leaves in order to understand the role of these phytohormones in the signalling network involved in the coffee defence response against Hemileia vastatrix. The results showed that the method was specific, linear (r ≥ 0.99) in the range 0.125-1.00 µg mL⁻¹ for JA and ABA and 0.125-5.00 µg mL⁻¹ for SA, and precise (relative standard deviation ≤11%), and the limit of detection (0.010 µg g⁻¹ fresh weight) was adequate for quantifying these phytohormones in this type of matrix.. In comparison with healthy leaves, those infected with H. vastatrix (resistance reaction) displayed an increase in SA level 24 h after inoculation, suggesting the involvement of an SA-dependent pathway in coffee resistance.

Topics: Abscisic Acid; Chromatography, High Pressure Liquid; Coffea; Cyclopentanes; Disease Resistance; Fungi; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Reproducibility of Results; Salicylic Acid; Signal Transduction; Spectrometry, Mass, Electrospray Ionization; Tandem Mass Spectrometry

Jasmonic acid (JA) is involved in the regulation of host immunity in plants. Recently, we demonstrated that JA signalling has an important role in resistance to rice bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) in rice. Here, we report that many volatile compounds accumulate in response to exogenous application of JA, including the monoterpene linalool. Expression of linalool synthase was up-regulated by JA. Vapour treatment with linalool induced resistance to Xoo, and transgenic rice plants overexpressing linalool synthase were more resistance to Xoo, presumably due to the up-regulation of defence-related genes in the absence of any treatment. JA-induced accumulation of linalool was regulated by OsJAZ8, a rice jasmonate ZIM-domain protein involving the JA signalling pathway at the transcriptional level, suggesting that linalool plays an important role in JA-induced resistance to Xoo in rice.

Topics: Acyclic Monoterpenes; Cyclopentanes; Disease Resistance; Metabolic Networks and Pathways; Molecular Sequence Data; Monoterpenes; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Signal Transduction; Transcriptome; Xanthomonas

Gray mold (Botrytis cinerea) is an important disease of tomato (Solanum lycopersicum). This study examined defense-related gene expression involved in the resistance to B. cinerea that is induced in tomato plants by benzothiadiazole and Trichoderma harzianum T39 soil drench. In whole plants, transcriptional changes related to salicylic acid and ethylene were induced by the application of a 0.01% benzothiadiazole solution, whereas changes related to jasmonic acid were induced by the application of a 0.4% T39 suspension. On detached leaves, soil treatment by T39 led to enhanced resistance to B. cinerea infection that was proportional to the concentration of the T39 suspension. By 5 days after pathogen inoculation, the plants that had received the 0.04% T39 drench exhibited 62% less severe disease than the untreated plants. The 0.4% T39 drench led to an 84% reduction in disease severity. Observations of B. cinerea infection in leaves harvested from plants grown in the treated soils revealed that drenching with a T39 suspension induces systemic resistance against B. cinerea and primes salicylic acid- and ethylene-related gene expression in a manner proportional to the concentration of the biocontrol agent. Benzothiadiazole treatment induced resistance to gray mold independently of salicylic acid and led to strong priming of two genes known to be involved in defense against B. cinerea, Pti5 and PI2.

Topics: Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; RNA, Messenger; RNA, Plant; Salicylic Acid; Solanum lycopersicum; Thiadiazoles; Trichoderma

The plant cell wall constitutes an essential protection barrier against pathogen attack. In addition, cell-wall disruption leads to accumulation of jasmonates (JAs), which are key signaling molecules for activation of plant inducible defense responses. However, whether JAs in return modulate the cell-wall composition to reinforce this defensive barrier remains unknown. The enzyme 13-allene oxide synthase (13-AOS) catalyzes the first committed step towards biosynthesis of JAs. In potato (Solanum tuberosum), there are two putative St13-AOS genes, which we show here to be differentially induced upon wounding. We also determine that both genes complement an Arabidopsis aos null mutant, indicating that they encode functional 13-AOS enzymes. Indeed, transgenic potato plants lacking both St13-AOS genes (CoAOS1/2 lines) exhibited a significant reduction of JAs, a concomitant decrease in wound-responsive gene activation, and an increased severity of soft rot disease symptoms caused by Dickeya dadantii. Intriguingly, a hypovirulent D. dadantii pel strain lacking the five major pectate lyases, which causes limited tissue maceration on wild-type plants, regained infectivity in CoAOS1/2 plants. In line with this, we found differences in pectin methyl esterase activity and cell-wall pectin composition between wild-type and CoAOS1/2 plants. Importantly, wild-type plants had pectins with a lower degree of methyl esterification, which are the substrates of the pectate lyases mutated in the pel strain. These results suggest that, during development of potato plants, JAs mediate modification of the pectin matrix to form a defensive barrier that is counteracted by pectinolytic virulence factors from D. dadantii.

Topics: Arabidopsis; Bacterial Proteins; Carboxylic Ester Hydrolases; Cell Wall; Cyclopentanes; Disease Resistance; Enterobacteriaceae; Esterification; Host-Pathogen Interactions; Intramolecular Oxidoreductases; Mutation; Oxylipins; Pectins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Polysaccharide-Lyases; Solanum tuberosum; Virulence Factors; Wounds and Injuries

Oxylipins produced by the 13-lipoxygenase (LOX) have been reported to play an important role in plant defense responses to herbivores. Yet, the role of oxylipins produced by the 9-LOX pathway in this process remains largely unknown. Here we cloned a gene encoding a chloroplast-localized 9-LOX, Osr9-LOX1, from rice. Transcriptional analysis revealed that herbivore infestation, mechanical wounding and jasmonic acid (JA) treatment either repressed or did not enhance the level of Osr9-LOX1 transcripts at early stages but did at later stages, whereas salicylic acid (SA) treatment quickly increased the transcript level of Osr9-LOX1. Antisense expression of Osr9-lox1 (as-r9lox1) decreased the amount of wound-induced (Z)-3-hexenal but increased levels of striped stem borer (SSB)-induced linolenic acid, JA, SA and trypsin protease inhibitors. These changes were associated with increased resistance in rice to the larvae of the SSB Chilo suppressalis. In contrast, although no significant differences were observed in the duration of the nymph stage or the number of eggs laid by female adults between the brown planthopper (BPH) Nilaparvata lugens that fed on as-r9lox1 lines and BPH that fed on wild-type (WT) rice plants, the survival rate of BPH nymphs that fed on as-r9lox1 lines was higher than that of nymphs that fed on WT plants, possibly because of a higher JA level. The results demonstrate that Osr9-LOX1 plays an important role in regulating an herbivore-induced JA burst and cross-talk between JA and SA, and in controlling resistance in rice to chewing and phloem-feeding herbivores.

Topics: Animals; Chloroplasts; Cyclopentanes; Disease Resistance; Female; Gene Expression Regulation, Plant; Hemiptera; Herbivory; Lepidoptera; Lipoxygenase; Oryza; Oxylipins; Plant Growth Regulators; Plant Proteins; Plant Stems; Plants, Genetically Modified; Reverse Genetics; Salicylic Acid

Systemic resistance is induced by pathogens and confers protection against a broad range of pathogens. Recent studies have indicated that salicylic acid (SA) derivative methyl salicylate (MeSA) serves as a long-distance phloem-mobile systemic resistance signal in tobacco, Arabidopsis, and potato. However, other experiments indicate that jasmonic acid (JA) is a critical mobile signal. Here, we present evidence suggesting both MeSA and methyl jasmonate (MeJA) are essential for systemic resistance against Tobacco mosaic virus (TMV), possibly acting as the initiating signals for systemic resistance. Foliar application of JA followed by SA triggered the strongest systemic resistance against TMV. Furthermore, we use a virus-induced gene-silencing-based genetics approach to investigate the function of JA and SA biosynthesis or signaling genes in systemic response against TMV infection. Silencing of SA or JA biosynthetic and signaling genes in Nicotiana benthamiana plants increased susceptibility to TMV. Genetic experiments also proved the irreplaceable roles of MeSA and MeJA in systemic resistance response. Systemic resistance was compromised when SA methyl transferase or JA carboxyl methyltransferase, which are required for MeSA and MeJA formation, respectively, were silenced. Moreover, high-performance liquid chromatography-mass spectrometry analysis indicated that JA and MeJA accumulated in phloem exudates of leaves at early stages and SA and MeSA accumulated at later stages, after TMV infection. Our data also indicated that JA and MeJA could regulate MeSA and SA production. Taken together, our results demonstrate that (Me)JA and (Me)SA are required for systemic resistance response against TMV.

Topics: Acetates; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Silencing; Genes, Reporter; Nicotiana; Oxylipins; Phloem; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Salicylates; Salicylic Acid; Signal Transduction; Tobacco Mosaic Virus

Grapevine (Vitis vinifera) is susceptible to many pathogens which cause significant losses to viticulture worldwide. Chemical control is available, but agro-ecological concerns have raised interest in alternative methods, especially in triggering plant immunity by elicitor treatments. The β-glucan laminarin (Lam) and its sulfated derivative (PS3) have been previously demonstrated to induce resistance in grapevine against downy mildew (Plasmopara viticola). However, if Lam elicits classical grapevine defenses such as oxidative burst, pathogenesis-related (PR)-proteins and phytoalexin production, PS3 triggered grapevine resistance via a poorly understood priming phenomenon. The aim of this study was to identify the molecular mechanisms of the PS3-induced resistance. For this purpose we studied i) the signaling events and transcriptome reprogramming triggered by PS3 treatment on uninfected grapevine, ii) grapevine immune responses primed by PS3 during P. viticola infection. Our results showed that i) PS3 was unable to elicit reactive oxygen species (ROS) production, cytosolic Ca(2+) concentration variations, mitogen-activated protein kinase (MAPK) activation but triggered a long lasting plasma membrane depolarization in grapevine cells, ii) PS3 and Lam shared a common stress-responsive transcriptome profile that partly overlapped the salicylate- (SA) and jasmonate-(JA)-dependent ones. After P. viticola inoculation, PS3 specifically primed the SA- and ROS-dependent defense pathways leading to grapevine induced resistance against this biotroph. Interestingly pharmacological approaches suggested that the plasma membrane depolarization and the downstream ROS production are key events of the PS3-induced resistance.

Topics: beta-Glucans; Cell Death; Cell Membrane; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Oomycetes; Oxylipins; Plant Diseases; Plant Immunity; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Stress, Physiological; Transcriptome; Vitis

Streptomyces scabies is a causal agent of common scab of potato, which generates necrotic tuber lesions. We have previously demonstrated that inoculation of potato plants with phenazine-1-carboxylic acid (PCA)- producing Pseudomonas sp. LBUM223 could significantly reduce common scab symptoms. In the present study, we investigated whether LBUM223 or an isogenic phzC- mutant not producing PCA could elicit an induced systemic resistance response in potato. The expression of eight defense-related genes (salicylic acid [SA]-related ChtA, PR-1b, PR-2, and PR-5; and jasmonic acid and ethylene-related LOX, PIN2, PAL-2, and ERF3) was quantified using newly developed TaqMan reverse-transcription quantitative polymerase chain reaction assays in 5- and 10-week-old potted potato plants. Although only wild-type LBUM223 was capable of significantly reducing common scab symptoms, the presence of both LBUM223 and its PCA-deficient mutant were equally able to upregulate the expression of LOX and PR-5. The presence of S. scabies overexpressed all SA-related genes. This indicates that (i) upregulation of potato defense-related genes by LBUM223 is unlikely to contribute to common scab's control and (ii) LBUM223's capacity to produce PCA is not involved in this upregulation. These results suggest that a direct interaction occurring between S. scabies and PCA-producing LBUM223 is more likely involved in controlling common scab development.

Topics: Cyclopentanes; Disease Resistance; Down-Regulation; Ethylenes; Gene Expression Regulation, Plant; Mutation; Oxylipins; Pest Control, Biological; Phenazines; Plant Diseases; Plant Growth Regulators; Plant Proteins; Pseudomonas; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Solanum tuberosum; Streptomyces; Up-Regulation

The extensively studied Arabidopsis phytoalexin deficient 4 (AtPAD4) gene plays an important role in Arabidopsis disease resistance; however, the function of its sequence ortholog in rice is unknown. Here, we show that rice OsPAD4 appears not to be the functional ortholog of AtPAD4 in host-pathogen interactions, and that the OsPAD4 encodes a plasma membrane protein but that AtPAD4 encodes a cytoplasmic and nuclear protein. Suppression of OsPAD4 by RNA interference (RNAi) increased rice susceptibility to the biotrophic pathogen Xanthomonas oryzae pv. oryzae (Xoo), which causes bacteria blight disease in local tissue. OsPAD4-RNAi plants also show compromised wound-induced systemic resistance to Xoo. The increased susceptibility to Xoo was associated with reduced accumulation of jasmonic acid (JA) and phytoalexin momilactone A (MOA). Exogenous application of JA complemented the phenotype of OsPAD4-RNAi plants in response to Xoo. The following results suggest that OsPAD4 functions differently than AtPAD4 in response to pathogen infection. First, OsPAD4 plays an important role in wound-induced systemic resistance, whereas AtPAD4 mediates systemic acquired resistance. Second, OsPAD4-involved defense signaling against Xoo is JA-dependent, but AtPAD4-involved defense signaling against biotrophic pathogens is salicylic acid-dependent. Finally, OsPAD4 is required for the accumulation of terpenoid-type phytoalexin MOA in rice-bacterium interactions, but AtPAD4-mediated resistance is associated with the accumulation of indole-type phytoalexin camalexin.

Topics: Amino Acid Sequence; Arabidopsis; Arabidopsis Proteins; Carboxylic Ester Hydrolases; Cell Membrane; Cyclopentanes; Disease Resistance; Diterpenes; Gene Expression Regulation, Plant; Green Fluorescent Proteins; Host-Pathogen Interactions; Membrane Proteins; Molecular Sequence Data; Oryza; Oxylipins; Phylogeny; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Protoplasts; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Salicylic Acid; Sequence Homology, Amino Acid; Stress, Mechanical; Xanthomonas

Blast, caused by the fungus Magnaporthe oryzae, is one of the most devastating diseases of rice worldwide. Phenylalanine ammonia lyase (PAL) is a key enzyme in the phenylpropanoid pathway, which leads to the biosynthesis of defense-related phytohormone salicylic acid (SA) and flavonoid-type phytoalexins sakuranetin and naringenin. However, the roles and biochemical features of individual rice PALs in defense responses to pathogens remain unclear. Here, we report that rice OsPAL06, which can catalyze the formation of trans-cinnamate using l-phenylalanine, is involved in rice root-M. oryzae interaction. OsPAL06-knockout mutant showed increased susceptibility to M. oryzae invaded from roots and developed typical leaf blast symptoms, accompanied by nearly complete disappearance of sakuranetin and naringenin and a two-third reduction of the SA level in roots. This mutant also showed compensatively induced expression of chalcone synthase, which is involved in flavonoid biosynthesis, isochorismate synthase 1, which is putatively involved in SA synthesis via another pathway, reduced jasmonate content and increased ethylene content. These results suggest that OsPAL06 is a positive regulator in preventing M. oryzae infection from roots. It may regulate defense by promoting both phytoalexin accumulation and SA signaling that synergistically and antagonistically interacts with jasmonate- and ethylene-dependent signaling, respectively.

Topics: Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Gene Knockout Techniques; Host-Pathogen Interactions; Magnaporthe; Oryza; Oxylipins; Phenylalanine Ammonia-Lyase; Phytoalexins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plant Roots; Salicylic Acid; Sesquiterpenes; Signal Transduction

Verticillium longisporum is a soil-borne vascular pathogen infecting cruciferous hosts such as oilseed rape. Quantitative disease resistance (QDR) is the major control means, but its molecular basis is poorly understood so far. Quantitative trait locus (QTL) mapping was performed using a new (Bur×Ler) recombinant inbred line (RIL) population of Arabidopsis thaliana. Phytohormone measurements and analyses in defined mutants and near-isogenic lines (NILs) were used to identify genes and signalling pathways that underlie different resistance QTL.. QTL for resistance to V. longisporum-induced stunting, systemic colonization by the fungus and for V. longisporum-induced chlorosis were identified. Stunting resistance QTL were contributed by both parents. The strongest stunting resistance QTL was shown to be identical with Erecta. A functional Erecta pathway, which was present in Bur, conferred partial resistance to V. longisporum-induced stunting. Bur showed severe stunting susceptibility in winter. Three stunting resistance QTL of Ler origin, two co-localising with wall-associated kinase-like (Wakl)-genes, were detected in winter. Furthermore, Bur showed a much stronger induction of salicylic acid (SA) by V. longisporum than Ler. Systemic colonization was controlled independently of stunting. The vec1 QTL on chromosome 2 had the strongest effect on systemic colonization. The same chromosomal region controlled the level of abscisic acid (ABA) and jasmonic acid (JA) in response to V. longisporum: The level of ABA was higher in colonization-susceptible Ler than in colonization-resistant Bur after V. longisporum infection. JA was down-regulated in Bur after infection, but not in Ler. These differences were also demonstrated in NILs, varying only in the region containing vec1. All phytohormone responses were shown to be independent of Erecta.. Signalling systems with a hitherto unknown role in the QDR of A. thaliana against V. longisporum were identified: Erecta mediated resistance against V. longisporum-induced stunting. Independent of Erecta, stunting was caused in a light-dependent manner with possible participation of SA and Wakl genes. ABA and JA showed a genotype-specific response that corresponded with systemic colonization by the fungus. Understanding the biological basis of phenotypic variation in A. thaliana with respect to V. longisporum resistance will provide new approaches for implementing durable resistance in cruciferous crops.

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Genetic Markers; Inbreeding; Light; Mutation; Oxylipins; Phenotype; Physical Chromosome Mapping; Plant Diseases; Protein Serine-Threonine Kinases; Quantitative Trait Loci; Quantitative Trait, Heritable; Receptors, Cell Surface; Salicylic Acid; Signal Transduction; Verticillium

The behavior of naturally virulent Meloidogyne isolates toward the tomato resistance gene Mi in major tomato-growing areas in Israel was studied for the first time. Virulence of seven selected isolates was confirmed over three successive generations on resistant (Mi-carrying) and susceptible (non-Mi-carrying) tomato cultivars. Diagnostic markers verified the predominance of Meloidogyne javanica among virulent isolates selected on resistant tomato cultivars or rootstocks. To better understand the determinants of nematode selection on Mi-carrying plants, reproduction of Mi-avirulent and virulent isolates Mjav1 and Mjv2, respectively, measured as eggs per gram of root, on non-Mi-carrying, heterozygous (Mi/mi) and homozygous (Mi/Mi) genotypes was evaluated. Although no reproduction of Mjav1 was observed on Mi/Mi genotypes, some reproduction was consistently observed on Mi/mi plants; reproduction of Mjv2 on the homozygous and heterozygous genotypes was similar to that on susceptible cultivars, suggesting a limited quantitative effect of the Mi gene. Histological examination of giant cells induced by Mi-virulent versus avirulent isolates confirmed the high virulence of Mjv2 on Mi/mi and Mi/Mi genotypes, allowing the formation of well-developed giant-cell systems despite the Mi gene. Analysis of the plant defense response in tomato Mi/Mi, Mi/mi, and mi/mi genotypes to both avirulent and virulent isolates was investigated by quantitative real-time polymerase chain reaction. Although the jasmonate (JA)-signaling pathway was clearly upregulated by avirulent and virulent isolates on the susceptible (not carrying Mi) and heterozygous (Mi/mi) plants, no change in signaling was observed in the homozygous (Mi/Mi) resistant line following incompatible interaction with the avirulent isolate. Thus, similar to infection promoted by the avirulent isolate on the susceptible genotype, the Mi-virulent isolate induced the JA-dependent pathway, which might promote tomato susceptibility during the compatible interaction with the homozygous (Mi/Mi) resistant line. These results have important consequences for the management of Mi resistance genes for ensuring sustainable tomato farming.

Topics: Animals; Cyclopentanes; Disease Resistance; DNA Primers; Genotype; Host-Parasite Interactions; Israel; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Reproduction; Salicylates; Signal Transduction; Solanum lycopersicum; Tylenchoidea; Virulence

Extensive studies using the model system Arabidopsis thaliana to elucidate plant defense signaling and pathway networks indicate that salicylic acid (SA) is the key hormone triggering the plant defense response against biotrophic and hemi-biotrophic pathogens, while jasmonic acid (JA) and derivatives are critical to the defense response against necrotrophic pathogens. Several reports demonstrate that SA limits nematode reproduction.. Here we translate knowledge gained from studies using Arabidopsis to soybean. The ability of thirty-one Arabidopsis genes encoding important components of SA and JA synthesis and signaling in conferring resistance to soybean cyst nematode (SCN: Heterodera glycines) are investigated. We demonstrate that overexpression of three of thirty-one Arabidoposis genes in transgenic soybean roots of composite plants decreased the number of cysts formed by SCN to less than 50% of those found on control roots, namely AtNPR1(33%), AtTGA2 (38%), and AtPR-5 (38%). Three additional Arabidopsis genes decreased the number of SCN cysts by 40% or more: AtACBP3 (53% of the control value), AtACD2 (55%), and AtCM-3 (57%). Other genes having less or no effect included AtEDS5 (77%), AtNDR1 (82%), AtEDS1 (107%), and AtPR-1 (80%), as compared to control. Overexpression of AtDND1 greatly increased susceptibility as indicated by a large increase in the number of SCN cysts (175% of control).. Knowledge of the pathogen defense system gained from studies of the model system, Arabidopsis, can be directly translated to soybean through direct overexpression of Arabidopsis genes. When the genes, AtNPR1, AtGA2, and AtPR-5, encoding specific components involved in SA regulation, synthesis, and signaling, are overexpressed in soybean roots, resistance to SCN is enhanced. This demonstrates functional compatibility of some Arabidopsis genes with soybean and identifies genes that may be used to engineer resistance to nematodes.

Topics: Amino Acid Sequence; Animals; Arabidopsis; Arabidopsis Proteins; Basic-Leucine Zipper Transcription Factors; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Glycine max; Molecular Sequence Data; Nuclear Proteins; Oxylipins; Plant Diseases; Plant Roots; Plants, Genetically Modified; RNA, Messenger; Salicylic Acid; Sequence Alignment; Signal Transduction; Transformation, Genetic; Tylenchoidea

Functional characterization of a defensin, J1-1, was conducted to evaluate its biotechnological potentiality in transgenic pepper plants against the causal agent of anthracnose disease, Colletotrichum gloeosporioides. To determine antifungal activity, J1-1 recombinant protein was generated and tested for the activity against C. gloeosporioides, resulting in 50% inhibition of fungal growth at a protein concentration of 0.1 mg·mL-1. To develop transgenic pepper plants resistant to anthracnose disease, J1-1 cDNA under the control of 35S promoter was introduced into pepper via Agrobacterium-mediated genetic transformation method. Southern and Northern blot analyses confirmed that a single copy of the transgene in selected transgenic plants was normally expressed and also stably transmitted to subsequent generations. The insertion of T-DNA was further analyzed in three independent homozygous lines using inverse PCR, and confirmed the integration of transgene in non-coding region of genomic DNA. Immunoblot results showed that the level of J1-1 proteins, which was not normally accumulated in unripe fruits, accumulated high in transgenic plants but appeared to differ among transgenic lines. Moreover, the expression of jasmonic acid-biosynthetic genes and pathogenesis-related genes were up-regulated in the transgenic lines, which is co-related with the resistance of J1-1 transgenic plants to anthracnose disease. Consequently, the constitutive expression of J1-1 in transgenic pepper plants provided strong resistance to the anthracnose fungus that was associated with highly reduced lesion formation and fungal colonization. These results implied the significance of the antifungal protein, J1-1, as a useful agronomic trait to control fungal disease.

Topics: Capsicum; Colletotrichum; Cyclopentanes; Defensins; Disease Resistance; Fruit; Gene Expression; Organ Specificity; Oxylipins; Plant Diseases; Plants, Genetically Modified; Recombinant Proteins; RNA, Messenger

We experimentally examined the effects of elevated O₃ and whitefly herbivory on tomato volatiles, feeding and oviposition preferences of whiteflies and behavioural responses of Encarsia formosa to these emissions on two tomato genotypes, a wild-type (Wt) and a jasmonic acid (JA) defence-enhanced genotype (JA-OE, 35S). The O₃ level and whitefly herbivory significantly increased the total amount of volatile organic compounds (VOCs), monoterpenes, green leaf volatiles (GLVs), and aldehyde volatiles produced by tomato plants. The 35S plants released higher amount of total VOCs and monoterpene volatiles than Wt plants under O₃+herbivory treatments. The feeding and oviposition bioassays showed that control plants were preferred by adult whiteflies whereas the 35S plants were not preferred by whiteflies. In the Y-tube tests, O₃+herbivory treatment genotypes were preferred by adult E. Formosa. The 35S plants were preferred by adult E. formosa under O₃, herbivory and O₃+herbivory treatments. Our results demonstrated that elevated O₃ and whitefly herbivory significantly increased tomato volatiles, which attracted E. formosa and reduced whitefly feeding. The 35S plants had a higher resistance to B. tabaci than Wt plant. Such changes suggest that the direct and indirect defences of resistant genotypes, such as 35S, could strengthen as the atmospheric O₃ concentration increases.

Topics: Aldehydes; Animals; Biosynthetic Pathways; Cyclopentanes; Disease Resistance; Dose-Response Relationship, Drug; Feeding Behavior; Female; Genotype; Hemiptera; Host-Parasite Interactions; Monoterpenes; Mutation; Oviposition; Oxylipins; Ozone; Plant Diseases; Plants, Genetically Modified; Solanum lycopersicum; Volatile Organic Compounds; Wasps

WRKY proteins are involved in various physiological processes in plants, especially in coping with diverse biotic and abiotic stresses. However, limited information is available on the roles of specific WRKY transcription factors in poplar defense. In this study, we reported the characterization of PtoWRKY60, a Group IIa WRKY member, from Populus tomentosa Carr. The gene expression profile of PtoWRKY60 in various tissues showed that it significantly accumulated in old leaves. Phylogenetic analyses revealed that PtoWRKY60 had a close relationship with AtWRKY18, AtWRKY40 and AtWRKY60. PtoWRKY60 was induced mainly by salicylic acid (SA) and slightly by Dothiorella gregaria Sacc., jasmonic acid, wounding treatment, low temperature and salinity stresses. Overexpression of PtoWRKY60 in poplar resulted in increased resistance to D. gregaria. The defense-associated genes, such as PR5.1, PR5.2, PR5.4, PR5.5 and CPR5, were markedly up-regulated in transgenic plants overexpressing PtoWRKY60. These results indicate that PtoWRKY60 might be partly involved in the signal transduction pathway initiated by SA in Populus.

Topics: Ascomycota; Cold Temperature; Cyclopentanes; Disease Resistance; Evolution, Molecular; Gene Expression Regulation, Plant; Organ Specificity; Oxylipins; Plant Diseases; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Populus; Salicylic Acid; Salinity; Transcription Factors

Plants have evolved an elaborate signaling network to ensure an appropriate level of immune response to meet the differing demands of developmental processes. Previous research has demonstrated that DELLA proteins physically interact with JASMONATE ZIM-DOMAIN1 (JAZ1) and dynamically regulate the interaction of the gibberellin (GA) and jasmonate (JA) signaling pathways. However, whether and how the JAZ1-DELLA regulatory node is regulated at the transcriptional level in plants under normal growth conditions or during pathogen infection is not known. Here, we demonstrate multiple functions of cotton (Gossypium barbadense) GbWRKY1 in the plant defense response and during development. Although GbWRKY1 expression is induced rapidly by methyl jasmonate and infection by Verticillium dahliae, our results show that GbWRKY1 is a negative regulator of the JA-mediated defense response and plant resistance to the pathogens Botrytis cinerea and V. dahliae. Under normal growth conditions, GbWRKY1-overexpressing lines displayed GA-associated phenotypes, including organ elongation and early flowering, coupled with the down-regulation of the putative targets of DELLA. We show that the GA-related phenotypes of GbWRKY1-overexpressing plants depend on the constitutive expression of Gossypium hirsutum GhJAZ1. We also show that GhJAZ1 can be transactivated by GbWRKY1 through TGAC core sequences, and the adjacent sequences of this binding site are essential for binding specificity and affinity to GbWRKY1, as revealed by dual-luciferase reporter assays and electrophoretic mobility shift assays. In summary, our data suggest that GbWRKY1 is a critical regulator mediating the plant defense-to-development transition during V. dahliae infection by activating JAZ1 expression.

Topics: Acetates; Cyclopentanes; Disease Resistance; Down-Regulation; Gene Expression Regulation, Plant; Gibberellins; Gossypium; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Verticillium

The plant galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) have been linked to the anti-inflammatory and cancer benefits of a green leafy vegetable diet in humans due to their ability to regulate the levels of free radicals like nitric oxide (NO). Here, we show that DGDG contributes to plant NO as well as salicylic acid biosynthesis and is required for the induction of systemic acquired resistance (SAR). In contrast, MGDG regulates the biosynthesis of the SAR signals azelaic acid (AzA) and glycerol-3-phosphate (G3P) that function downstream of NO. Interestingly, DGDG is also required for AzA-induced SAR, but MGDG is not. Notably, transgenic expression of a bacterial glucosyltransferase is unable to restore SAR in dgd1 plants even though it does rescue their morphological and fatty acid phenotypes. These results suggest that MGDG and DGDG are required at distinct steps and function exclusively in their individual roles during the induction of SAR.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Galactolipids; Galactosyltransferases; Lipid Metabolism; Nitric Oxide; Oxylipins; Plant Diseases; Salicylic Acid

Small GTPases are monomeric guanine nucleotide-binding proteins. In plants, ROPs regulate plant cell polarity, plant cell differentiation and development as well as biotic and abiotic stress signaling pathways.. We report the subcellular localization of the AtRop1 protein at the plasma membrane in tobacco epidermal cells using GFP fusions. Additionally, transient and stable expression of a dominant negative form (DN) of the Arabidopsis AtRop1 in potato led to H2O2 accumulation associated with the reduced development of Phytophthora infestans Montagne de Bary and smaller lesions on infected potato leaves. The expression of the Strboh-D gene, a NADPH oxidase homologue in potato, was analyzed by RT-PCR. Expression of this gene was maintained in DN-AtRop1 transgenic plants after infection with P. infestans. In transgenic potato lines, the transcript levels of salicylic acid (SA) and jasmonic acid (JA) marker genes (Npr1 and Lox, respectively) were analyzed. The Lox gene was induced dramatically whereas expression of Npr1, a gene up-regulated by SA, decreased slightly in DN-AtRop1 transgenic plants after infection with P. infestans.. In conclusion, our results indicate that DN-AtROP1 affects potato resistance to P. infestans. This is associated with increased NADPH oxidase-mediated H2O2 production and JA signaling.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; GTP-Binding Proteins; Host-Pathogen Interactions; Hydrogen Peroxide; Multienzyme Complexes; NADH, NADPH Oxidoreductases; Oxylipins; Phytophthora infestans; Plant Diseases; Solanum tuberosum

The plant hormone jasmonic acid (JA) has a crucial role in defense responses against pathogens in rice. We recently reported that some volatile compounds accumulate in response to JA treatment, and that the monoterpene linalool plays an important role in JA-induced resistance to rice bacterial blight caused by Xanthomonas oryzae pv oryzae (Xoo) in rice. One of the JA-responsive volatiles, (E,E)-2,4-heptadienal, has both antibacterial and antifungal activity against Xoo, and the rice fungal pathogen Magnaporthe oryzae. In addition, (E,E)-2,4-heptadienal was toxic to rice plants. These phenomena were not observed when linalool was treated. These results indicate that accumulation of the (E,E)-2,4-heptadienal in response to JA is a double-edged sword, but it is essential for survival against pathogen attacks in rice.

Topics: Acyclic Monoterpenes; Aldehydes; Alkadienes; Amino Acid Sequence; Cyclopentanes; Disease Resistance; Magnaporthe; Monoterpenes; Oils, Volatile; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Xanthomonas

Gibberellins (GA) are phytohormones controlling major aspects of plant lifecycle including seed germination, growth and flower development. GA signaling is also involved in resistance to adverse conditions, thus providing a mechanism for environmentally responsive growth regulation. We recently characterized the function of a core component of the GA signal transduction pathway: RGL3. RGL3 belongs to the DELLA family of negative GA response regulators. Jasmonate (JA) rapidly induces RGL3 expression, which in turn enhances the expression of JA-responsive genes by inhibiting the activity of key repressors of JA signaling, the JAZ proteins. JA and ethylene (ET) are well known to play synergistic roles in plant disease resistance. Accordingly, we showed that RGL3 regulates plant defense responses by modulating JA/ET-mediated defense signaling pathway.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Gibberellins; Oxylipins; Plant Diseases; Plant Growth Regulators; Repressor Proteins; Signal Transduction

Phytophthora cinnamomi is a soil-borne plant pathogen that has caused widespread damage to vulnerable native ecosystems and agriculture systems across the world and shows no sign of abating. Management of the pathogen in the natural environment is difficult and the options are limited. In order to discover more about how resistant plants are able to defend themselves against this generalist pathogen, a microarray study of plant gene expression following root inoculation with P. cinnamomi was undertaken. Zea mays was used as a resistant model plant, and microarray analysis was conducted using the Affymetrix GeneChip Maize Genome Array on root samples collected at 6- and 24-h post-inoculation. Over 300 genes were differentially expressed in inoculated roots compared with controls across the two time points. Following Gene Ontology enrichment analysis and REVIGO visualisation of the up-regulated genes, many were implicated in plant defence responses to biotic stress. Genes that were up-regulated included those involved in phytoalexin biosynthesis and jasmonic acid/ethylene biosynthesis and other defence-related genes including those encoding glutathione S-transferases and serine-protease inhibitors. Of particular interest was the identification of the two most highly up-regulated genes, terpene synthase11 (Tps11) and kaurene synthase2 (An2), which are both involved in production of terpenoid phytoalexins. This is the first study that has investigated gene expression at a global level in roots in response to P. cinnamomi in a model plant species and provides valuable insights into the mechanisms involved in defence.

Topics: Australia; Cyclopentanes; Databases, Genetic; Disease Resistance; Ecosystem; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Molecular Sequence Annotation; Nucleotide Motifs; Oligonucleotide Array Sequence Analysis; Oxylipins; Phytophthora; Plant Diseases; Plant Roots; Promoter Regions, Genetic; Reproducibility of Results; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Terpenes; Time Factors; Up-Regulation; Zea mays

A gene encoding a coproporphyrinogen III oxidase mediates disease resistance in plants by the salicylic acid pathway. A number of genes that regulate powdery mildew resistance have been identified in Arabidopsis, such as ENHANCED DISEASE RESISTANCE 1 to 3 (EDR1 to 3). To further study the molecular interactions between the powdery mildew pathogen and Arabidopsis, we isolated and characterized a mutant that exhibited enhanced resistance to powdery mildew. The mutant also showed dramatic powdery mildew-induced cell death as well as growth defects and early senescence in the absence of pathogens. We identified the affected gene by map-based cloning and found that the gene encodes a coproporphyrinogen III oxidase, a key enzyme in the tetrapyrrole biosynthesis pathway, previously known as LESION INITIATION 2 (LIN2). Therefore, we designated the mutant lin2-2. Further studies revealed that the lin2-2 mutant also displayed enhanced resistance to Hyaloperonospora arabidopsidis (H.a.) Noco2. Genetic analysis showed that the lin2-2-mediated disease resistance and spontaneous cell death were dependent on PHYTOALEXIN DEFICIENT 4 (PAD4), SALICYLIC ACID INDUCTION-DEFICIENT 2 (SID2), and NONEXPRESSOR OF PATHOGENESIS-RELATED GENES 1 (NPR1), which are all involved in salicylic acid signaling. Furthermore, the relative expression levels of defense-related genes were induced after powdery mildew infection in the lin2-2 mutant. These data indicated that LIN2 plays an important role in cell death control and defense responses in plants.

Topics: Arabidopsis; Arabidopsis Proteins; Ascomycota; Base Sequence; Cell Death; Coproporphyrinogen Oxidase; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Molecular Sequence Data; Mutation; Oomycetes; Oxylipins; Plant Diseases; Plants, Genetically Modified; Salicylic Acid

Maize rough dwarf disease (MRDD, a viral disease) results in significant grain yield losses, while genetic basis of which is largely unknown. Based on comparative genomics, eukaryotic translation initiation factor 4E (eIF4E) was considered as a candidate gene for MRDD resistance, validation of which will help to understand the possible genetic mechanism of this disease. ZmeIF4E (orthologs of eIF4E gene in maize) encodes a protein of 218 amino acids, harboring five exons and no variation in the cDNA sequence is identified between the resistant inbred line, X178 and susceptible one, Ye478. ZmeIF4E expression was different in the two lines plants treated with three plant hormones, ethylene, salicylic acid, and jasmonates at V3 developmental stage, suggesting that ZmeIF4E is more likely to be involved in the regulation of defense gene expression and induction of local and systemic resistance. Moreover, four cis-acting elements related to plant defense responses, including DOFCOREZM, EECCRCAH1, GT1GAMSCAM4, and GT1CONSENSUS were detected in ZmeIF4E promoter for harboring sequence variation in the two lines. Association analysis with 163 inbred lines revealed that one SNP in EECCRCAH1 is significantly associated with CSI of MRDD in two environments, which explained 3.33 and 9.04 % of phenotypic variation, respectively. Meanwhile, one SNP in GT-1 motif was found to affect MRDD resistance only in one of the two environments, which explained 5.17 % of phenotypic variation. Collectively, regulatory motifs respectively harboring the two significant SNPs in ZmeIF4E promoter could be involved in the defense process of maize after viral infection. These results contribute to understand maize defense mechanisms against maize rough dwarf virus.

Topics: Base Sequence; Cyclopentanes; Disease Resistance; Ethylenes; Eukaryotic Initiation Factor-4E; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Molecular Sequence Data; Nucleotide Motifs; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Polymorphism, Single Nucleotide; Promoter Regions, Genetic; Regulatory Sequences, Nucleic Acid; Reoviridae; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Sequence Analysis, DNA; Zea mays

· Small RNAs play important roles in resistance to plant viruses and the complex responses against pathogens and leaf-chewing insects. · We investigated whether small RNA pathways are involved in Arabidopsis resistance against a phloem-feeding insect, the green peach aphid (Myzus persicae). We used a 2-wk fecundity assay to assess aphid performance on Arabidopsis RNA silencing and defence pathway mutants. Quantitative real-time polymerase chain reaction was used to monitor the transcriptional activity of defence-related genes in plants of varying aphid susceptibility. High-performance liquid chromatography-mass spectrometry was employed to measure the accumulation of the antimicrobial compound camalexin. Artificial diet assays allowed the assessment of the effect of camalexin on aphid performance. · Myzus persicae produces significantly less progeny on Arabidopsis microRNA (miRNA) pathway mutants. Plants unable to process miRNAs respond to aphid infestation with increased induction of PHYTOALEXIN DEFICIENT3 (PAD3) and production of camalexin. Aphids ingest camalexin when feeding on Arabidopsis and are more successful on pad3 and cyp79b2/cyp79b3 mutants defective in camalexin production. Aphids produce less progeny on artificial diets containing camalexin. · Our data indicate that camalexin functions beyond antimicrobial defence to also include hemipteran insects. This work also highlights the extensive role of the miRNA-mediated regulation of secondary metabolic defence pathways with relevance to resistance against a hemipteran pest.

Topics: Animals; Aphids; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Ethylenes; Feeding Behavior; Fertility; Gene Expression Regulation, Plant; Indoles; MicroRNAs; Mutation; Oxylipins; Phloem; Plant Diseases; Prunus; Reproduction; Signal Transduction; Survival Analysis; Thiazoles; Up-Regulation

Plant cell wall modification is a critical component in stress responses. Endo-1,4-β-glucanases (EGs) take part in cell wall editing processes, e.g. elongation, ripening and abscission. Here we studied the infection response of Solanum lycopersicum and Arabidopsis thaliana with impaired EGs. Transgenic TomCel1 and TomCel2 tomato antisense plants challenged with Pseudomonas syringae showed higher susceptibility, callose priming and increased jasmonic acid pathway marker gene expression. These two EGs could be resistance factors and may act as negative regulators of callose deposition, probably by interfering with the defence-signalling network. A study of a set of Arabidopsis EG T-DNA insertion mutants challenged with P. syringae and Botrytis cinerea revealed that the lack of other EGs interferes with infection phenotype, callose deposition, expression of signalling pathway marker genes and hormonal balance. We conclude that a lack of EGs could alter plant response to pathogens by modifying the properties of the cell wall and/or interfering with signalling pathways, contributing to generate the appropriate signalling outcomes. Analysis of microarray data demonstrates that EGs are differentially expressed upon many different plant-pathogen challenges, hormone treatments and many abiotic stresses. We found some Arabidopsis EG mutants with increased tolerance to osmotic and salt stress. Our results show that impairing EGs can alter plant-pathogen interactions and may contribute to appropriate signalling outcomes in many different biotic and abiotic plant stress responses.

Topics: Arabidopsis; Botrytis; Cell Wall; Cellulase; Cyclopentanes; Disease Resistance; Gene Expression; Gene Expression Regulation, Plant; Genes, Plant; Glucans; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Pseudomonas syringae; Signal Transduction; Solanum lycopersicum

Rab proteins play an essential role in regulating vesicular transport in eukaryotic cells. Previously, we characterized OsRab11, which in concert with OsGAP1 and OsGDI3 regulates vesicular trafficking from the trans-Golgi network (TGN) to the plasma membrane or vacuole. To further elucidate the physiological function of OsRab11 in plants, we performed yeast two-hybrid screens using OsRab11 as bait. OsOPR8 was isolated and shown to interact with OsRab11. A co-immunoprecipitation assay confirmed this interaction. The green fluorescent protein-OsOPR8 fusion product was targeted to the cytoplasm and peroxisomes of protoplasts from Arabidopsis thaliana. OsOPR8 exhibited NADPH-dependent reduction activity when 2-cyclohexen-1-one (CyHE) and 12-oxo-phytodienoic acid (OPDA) were supplied as possible substrates. Interestingly, NADPH oxidation by OsOPR8 was increased when wild-type OsRab11 or the constitutively active form of OsRab11 (Q78L) were included in the reaction mix, but not when the dominant negative form of OsRab11 (S28N) was included. OsRab11 was expressed broadly in plants and both OsRab11 and OsOPR8 were induced by jasmonic acid (JA) and elicitor treatments. Overexpressed OsRab11 transgenic plants showed resistance to pathogens through induced expression of JA-responsive genes. In conclusion, OsRab11 may be required for JA-mediated defense signaling by activating the reducing activity of OsOPR8.

Topics: Amino Acid Sequence; Arabidopsis; Cyclopentanes; Cytoplasm; Disease Resistance; Gene Expression Regulation, Plant; Green Fluorescent Proteins; Host-Pathogen Interactions; Microscopy, Fluorescence; Molecular Sequence Data; Mutation; Oryza; Oxylipins; Peroxisomes; Plant Diseases; Plant Growth Regulators; Plant Proteins; Protein Binding; Protein Transport; Protoplasts; Pseudomonas syringae; rab GTP-Binding Proteins; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; Signal Transduction; Two-Hybrid System Techniques

Jasmonates, together with other plant hormones, are important orchestrators of the plant immune system. The different hormone-controlled signaling pathways cross-communicate in an antagonistic or a synergistic manner, providing the plant with a powerful capacity to finely regulate its immune response. Jasmonic acid (JA) signaling is required for plant resistance to harmful organisms, such as necrotrophic pathogens and herbivorous insects. Furthermore, JA signaling is essential in interactions of plants with beneficial microbes that induce systemic resistance to pathogens and insects. The role of JA signaling components in plant immunity can be studied by performing bioassays with different interacting organisms. Determination of the level of resistance and the induction of defense responses in plants with altered JA components, through mutation or ectopic expression, will unveil novel mechanisms of JA signaling. We provide detailed protocols of bioassays with the model plant Arabidopsis thaliana challenged with the pathogens Botrytis cinerea and Pseudomonas syringae, the insect herbivore Pieris rapae, and the beneficial microbe Pseudomonas fluorescens. In addition, we describe pharmacological assays to study the modulation of JA-regulated responses by exogenous application of combinations of hormones, because a simultaneous rise in hormone levels occurs during interaction of plants with other organisms.

Topics: Animals; Arabidopsis; Biological Assay; Botrytis; Butterflies; Cyclopentanes; Disease Resistance; Herbivory; Host-Pathogen Interactions; Insecta; Larva; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Pseudomonas fluorescens; Rhizobiaceae; Seedlings; Seeds; Signal Transduction

Many plant immune responses to biotic stress are mediated by the wound hormone jasmonate (JA). Functional and mechanistic studies of the JA signaling pathway often involve plant manipulations that elicit JA production and subsequent changes in gene expression in local and systemic tissues. Here, we describe a simple mechanical wounding procedure to effectively trigger JA responses in the Arabidopsis thaliana rosette. For comparison, we also present a plant-insect bioassay to elicit defense responses with the chewing insect Trichoplusia ni. This latter procedure can be used to determine the effect of JA-regulated defenses on growth and development of insect herbivores.

Topics: Animals; Arabidopsis; Butterflies; Cyclopentanes; Disease Resistance; Herbivory; Larva; Oxylipins; Plant Growth Regulators; Plant Leaves

Pseudomonas syringae pv. tomato DC30000 (Pst DC3000) infection of Arabidopsis thaliana has been widely used to elucidate many of the general principles underlying the plant immune response and bacterial pathogenesis. Study of Pst DC3000 virulence factors has also proven useful in the discovery and elucidation of fundamental mechanisms in plant biology. In particular, Pst DC3000 produces a phytotoxin, coronatine, that is a remarkable molecular mimic of the active form of the plant hormone jasmonate. Here we illustrate several common methods used for Pst DC3000-based assays, including preparation of Pst DC3000 inocula, inoculation of soil-grown Arabidopsis plants, and subsequent bacterial quantification in planta. We also describe how Pst DC3000 infection can be applied to study gene expression and protein degradation associated with jasmonate signaling.

Topics: Arabidopsis; Blotting, Western; Cyclopentanes; Disease Resistance; DNA, Complementary; Electrophoresis, Polyacrylamide Gel; Gene Expression Regulation, Plant; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Pseudomonas syringae; Real-Time Polymerase Chain Reaction; RNA, Messenger; RNA, Plant; Signal Transduction

Simultaneous mutation of two WRKY-type transcription factors, WRKY18 and WRKY40, renders otherwise susceptible wild-type Arabidopsis plants resistant towards the biotrophic powdery mildew fungus Golovinomyces orontii. Resistance in wrky18 wrky40 double mutant plants is accompanied by massive transcriptional reprogramming, imbalance in salicylic acid (SA) and jasmonic acid (JA) signaling, altered ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) expression, and accumulation of the phytoalexin camalexin. Genetic analyses identified SA biosynthesis and EDS1 signaling as well as biosynthesis of the indole-glucosinolate 4MI3G as essential components required for loss-of-WRKY18 WRKY40-mediated resistance towards G. orontii. The analysis of wrky18 wrky40 pad3 mutant plants impaired in camalexin biosynthesis revealed an uncoupling of pre- from postinvasive resistance against G. orontii. Comprehensive infection studies demonstrated the specificity of wrky18 wrky40-mediated G. orontii resistance. Interestingly, WRKY18 and WRKY40 act as positive regulators in effector-triggered immunity, as the wrky18 wrky40 double mutant was found to be strongly susceptible towards the bacterial pathogen Pseudomonas syringae DC3000 expressing the effector AvrRPS4 but not against other tested Pseudomonas strains. We hypothesize that G. orontii depends on the function of WRKY18 and WRKY40 to successfully infect Arabidopsis wild-type plants while, in the interaction with P. syringae AvrRPS4, they are required to mediate effector-triggered immunity.

Topics: Arabidopsis; Arabidopsis Proteins; Ascomycota; Botrytis; Cyclopentanes; Disease Resistance; DNA-Binding Proteins; Gene Expression Regulation, Plant; Glucosinolates; Indoles; Mutation; Oomycetes; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plants, Genetically Modified; Pseudomonas syringae; Salicylic Acid; Signal Transduction; Thiazoles; Transcription Factors

The emission of a specific blend of volatiles in response to Mythimna separata (herbivore-induced plant volatiles, HIPVs) plays a great ecological role by priming neighbouring plants. Maize plants placed downwind of infested, conspecific plants showed reduced larval development not only immediately after exposure to HIPVs but also when receiver plants were tested after a time lag of up to 5 days, compared to those exposed to volatiles from uninfested plants and tested after the same time lag. The molecular basis of this plant memory was, in part, the similarly recalled expression of a Bowman-Birk type trypsin inhibitor (TI) gene, in a jasmonic acid induction-independent manner. Moreover, in the promoter region of TI, a suite of methylation sites was found to be demethylated by the HIPV treatment. These findings provide an innovative mechanism for the epigenetic basis of the memory of HIPV-mediated habituation for plant defence.

Topics: Animals; Cyclopentanes; Disease Resistance; DNA Methylation; DNA, Plant; Epigenomics; Gene Expression Regulation, Plant; Herbivory; Larva; Oxylipins; Plant Diseases; Plant Physiological Phenomena; Plant Proteins; Promoter Regions, Genetic; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Volatile Organic Compounds; Zea mays

Plants evolve effective mechanisms to protect themselves from environmental stresses and employ jasmonates as vital defense signals to defend against insect attack and pathogen infection. Jasmonates are also recognized as an essential growth regulator by which diverse developmental processes are mediated. Despite substantial research, there are no key signaling components reported yet to control jasmonate-regulated plant defense independent of developmental responses. We identify JAV1, a key gene in the jasmonate pathway, which functions as a negative regulator to control plant defense but does not play a detectable role in plant development. Our results suggest that when encountering insect attack and pathogen infection, plants accumulate jasmonates that trigger JAV1 degradation via the 26S proteasome to activate defensive gene expression and elevate resistances against both insects and pathogens. These findings have provided insight into the molecular mechanism by which plants integrate jasmonate signals to protect themselves from insect attack and pathogen infection.

Topics: Amino Acid Sequence; Animals; Arabidopsis; Arabidopsis Proteins; Base Sequence; Blotting, Western; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Host-Parasite Interactions; Insecta; Intracellular Signaling Peptides and Proteins; Molecular Sequence Data; Mutation; Oligonucleotide Array Sequence Analysis; Oxylipins; Phylogeny; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; Sequence Homology, Amino Acid

Based on Arabidopsis microarray, we found 8 WRKY genes were up-regulated with Oxalic acid (OA) challenge, AtWRKY28 and AtWRKY75 overexpression lines showed enhanced resistance to OA and Sclerotinia sclerotiorum. The WRKY transcription factors are involved in various plant physiological processes and most remarkably in coping with diverse biotic and abiotic stresses. Oxalic acid (OA) is an important pathogenicity-determinant of necrotrophic phytopathogenic fungi, such as Sclerotina sclerotiorum (S. sclerotiorum) and Botrytis cinerea (B. cinerea). The identification of differentially expressed genes under OA stress should facilitate our understanding of the pathogenesis mechanism of OA-producing fungi in host plants, and the mechanism of how plants respond to OA and pathogen infection. Based on Arabidopsis oligo microarray, we found 8 WRKY genes that were up-regulated upon OA challenge. The Arabidopsis plants overexpressing AtWRKY28 and AtWRK75 showed enhanced resistance to OA and S. sclerotiorum simultaneously. Furthermore, our results showed that overexpression of AtWRKY28 and AtWRK75 induced oxidative burst in host plants, which suppressed the hyphal growth of S. sclerotiorum, and consequently inhibited fungal infection. Gene expression profiling indicates that both AtWRKY28 and AtWRKY75 are transcriptional regulators of salicylic acid (SA)- and jasmonic acid/ethylene (JA/ET)-dependent defense signaling pathways, AtWRKY28 and AtWRKY75 mainly active JA/ET pathway to defend Arabidopsis against S. sclerotiorum and oxalic acid stress.

Topics: Arabidopsis; Arabidopsis Proteins; Ascomycota; Cyclopentanes; Disease Resistance; DNA-Binding Proteins; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Oxalic Acid; Oxylipins; Plant Diseases; Plants, Genetically Modified; Respiratory Burst; Transcription Factors

Calcium-dependent protein kinases (CPKs) are important Ca2+ signalling components involved in complex immune and stress signalling networks; but the knowledge of CPK gene functions in the hexaploid wheat is limited. Previously, TaCPK2 was shown to be inducible by powdery mildew (Blumeria graminis tritici, Bgt) infection in wheat. Here, its functions in disease resistance are characterized further. This study shows the presence of defence-response and cold-response cis-elements on the promoters of the A subgenome homoeologue (TaCPK2-A) and D subgenome homoeologue (TaCPK2-D), respectively. Their expression patterns were then confirmed by quantitative real-time PCR (qRT-PCR) using genome-specific primers, where TaCPK2-A was induced by Bgt treatment while TaCPK2-D mainly responded to cold treatment. Downregulation of TaCPK2-A by virus-induced gene silencing (VIGS) causes loss of resistance to Bgt in resistant wheat lines, indicating that TaCPK2-A is required for powdery mildew resistance. Furthermore, overexpression of TaCPK2-A in rice enhanced bacterial blight (Xanthomonas oryzae pv. oryzae, Xoo) resistance. qRT-PCR analysis showed that overexpression of TaCPK2-A in rice promoted the expression of OsWRKY45-1, a transcription factor involved in both fungal and bacterial resistance by regulating jasmonic acid and salicylic acid signalling genes. The opposite effect was found in wheat TaCPK2-A VIGS plants, where the homologue of OsWRKY45-1 was significantly repressed. These data suggest that modulation of WRKY45-1 and associated defence-response genes by CPK2 genes may be the common mechanism for multiple disease resistance in grass species, which may have undergone subfunctionalization in promoters before the formation of hexaploid wheat.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Protein Kinases; Salicylic Acid; Triticum

Larix gmelinii is a dominant tree species in China's boreal forests and plays an important role in the coniferous ecosystem. It is also one of the most economically important tree species in the Chinese timber industry due to excellent water resistance and anti-corrosion of its wood products. Unfortunately, in Northeast China, L. gmelinii often suffers from serious attacks by diseases and insects. The application of exogenous volatile semiochemicals may induce and enhance its resistance against insect or disease attacks; however, little is known regarding the genes and molecular mechanisms related to induced resistance.. We performed de novo sequencing and assembly of the L. gmelinii transcriptome using a short read sequencing technology (Illumina). Chemical defenses of L. gmelinii seedlings were induced with jasmonic acid (JA) or methyl jasmonate (MeJA) for 6 hours. Transcriptomes were compared between seedlings induced by JA, MeJA and untreated controls using a tag-based digital gene expression profiling system. In a single run, 25,977,782 short reads were produced and 51,157 unigenes were obtained with a mean length of 517 nt. We sequenced 3 digital gene expression libraries and generated between 3.5 and 5.9 million raw tags, and obtained 52,040 reliable reference genes after removing redundancy. The expression of disease/insect-resistance genes (e.g., phenylalanine ammonialyase, coumarate 3-hydroxylase, lipoxygenase, allene oxide synthase and allene oxide cyclase) was up-regulated. The expression profiles of some abundant genes under different elicitor treatment were studied by using real-time qRT-PCR.The results showed that the expression levels of disease/insect-resistance genes in the seedling samples induced by JA and MeJA were higher than those in the control group. The seedlings induced with MeJA elicited the strongest increases in disease/insect-resistance genes.. Both JA and MeJA induced seedlings of L. gmelinii showed significantly increased expression of disease/insect-resistance genes. MeJA seemed to have a stronger induction effect than JA on expression of disease/insect-resistance related genes. This study provides sequence resources for L. gmelinii research and will help us to better understand the functions of disease/insect-resistance genes and the molecular mechanisms of secondary metabolisms in L. gmelinii.

Topics: Acetates; Chromosome Mapping; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Gene Ontology; Genes, Plant; Larix; Molecular Sequence Annotation; Open Reading Frames; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Seedlings; Transcriptional Activation; Transcriptome; Up-Regulation

Verticillium wilt causes massive annual losses of cotton yield, but the mechanism of cotton resistance to Verticillium dahliae is complex and poorly understood. In this study, a comparative proteomic analysis was performed in resistant cotton (Gossypium barbadense cv7124) on infection with V. dahliae. A total of 188 differentially expressed proteins were identified by mass spectrometry (MALDI-TOF/TOF) analysis and could be classified into 17 biological processes based on Gene Ontology annotation. Most of these proteins were implicated in stimulus response, cellular processes and metabolic processes. Based on the proteomic analysis, several genes involved in secondary metabolism, reactive oxygen burst and phytohormone signaling pathways were identified for further physiological and molecular analysis. The roles of the corresponding genes were further characterized by employing virus-induced gene silencing (VIGS). Based on the results, we suggest that the production of gossypol is sufficient to affect the cotton resistance to V. dahliae. Silencing of GbCAD1, a key enzyme involving in gossypol biosynthesis, compromised cotton resistance to V. dahliae. Reactive oxygen species and salicylic acid signaling may be also implicated as regulators in cotton responsive to V. dahliae according to the analysis of GbSSI2, an important regulator in the crosstalk between salicylic acid and jasmonic acid signal pathways. Moreover, brassinosteroids and jasmonic acid signaling may play essential roles in the cotton disease resistance to V. dahliae. The brassinosteroids signaling was activated in cotton on inoculation with V. dahliae and the disease resistance of cotton was enhanced after exogenous application of brassinolide. Meanwhile, jasmonic acid signaling was also activated in cotton after inoculation with V. dahliae and brassinolide application. These data provide highlights in the molecular basis of cotton resistance to V. dahliae.

Topics: Brassinosteroids; Cyclopentanes; Disease Resistance; Electrophoresis, Gel, Two-Dimensional; Gene Expression Regulation, Plant; Gene Silencing; Gossypium; Gossypol; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Proteins; Proteomics; Reactive Oxygen Species; RNA, Small Interfering; Salicylic Acid; Signal Transduction; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Steroids, Heterocyclic; Verticillium

Here, we analyzed the interaction between Arabidopsis (Arabidopsis thaliana) and the American serpentine leafminer (Liriomyza trifolii), an important and intractable herbivore of many cultivated plants. We examined the role of the immunity-related plant hormone jasmonate (JA) in the plant response and resistance to leafminer feeding to determine whether JA affects host suitability for leafminers. The expression of marker genes for the JA-dependent plant defense was induced by leafminer feeding on Arabidopsis wild-type plants. Analyses of JA-insensitive coi1-1 mutants suggested the importance of JA in the plant response to leafminer feeding. The JA content of wild-type plants significantly increased after leafminer feeding. Moreover, coi1-1 mutants showed lower feeding resistance against leafminer attack than did wild-type plants. The number of feeding scars caused by inoculated adult leafminers in JA-insensitive coi1-1 mutants was higher than that in wild-type plants. In addition, adults of the following generation appeared only from coi1-1 mutants and not from wild-type plants, suggesting that the loss of the JA-dependent plant defense converted nonhost plants to accessible host plants. Interestingly, the glucosinolate-myrosinase defense system may play at most a minor role in this conversion, indicating that this major antiherbivore defense of Brassica species plants probably does not have a major function in plant resistance to leafminer. Application of JA to wild-type plants before leafminer feeding enhanced feeding resistance in Chinese cabbage (Brassica rapa), tomato (Solanum lycopersicum), and garland chrysanthemum (Chrysanthemum coronarium). Our results indicate that JA plays an important role in the plant response and resistance to leafminers and, in so doing, affects host plant suitability for leafminers.

Topics: Animals; Arabidopsis; Arabidopsis Proteins; Brassica rapa; Chrysanthemum; Cyclopentanes; Defensins; Diptera; Disease Resistance; Feeding Behavior; Female; Gene Expression Regulation, Plant; Host-Parasite Interactions; Mutation; Oxylipins; Plant Diseases; Population Density; Reverse Transcriptase Polymerase Chain Reaction; Solanum lycopersicum; Transcription Factors

Ergosterol, a principal compound of the fungal plasma membrane, is regarded as a pathogen-associated molecular pattern. In the present study, the role of salicylic acid (SA), jasmonic acid (JA) and spermine signaling pathways after ergosterol elicitation were evaluated. SA, JA and spermine production, as well as accumulation of transcripts for a lipoxygenase (NaLOX3) gene, the phenylalanine-ammonia lyase gene, selected pathogenesis-related genes (PR1, PR5), and peroxidase tPOXC1 were determined in tobacco (Nicotiana tabacum L. cv. Xanthi) in response to ergosterol elicitation. To understand the sequence of the signaling cascade, several representative steps involved in the synthesis of crucial signaling molecules were targeted using specific inhibitors. SA signaling pathway, together with calmodulin-dependent protein kinases and nitric oxide, was demonstrated to play an important role in the induction of defense-related genes following ergosterol treatment. The results suggested that nitric oxide participates in defense-related gene activation following ergosterol treatment but does not directly participate in activation of reactive oxygen species production. The induction of PR5 and tPOXC1 transcripts was found to be not fully dependent on calmodulin/Ca2+ and SA signaling, contrary to the PR1a transcript. A possible candidate for this SA-independent pathway is the spermine pathway, as elevated spermine levels were detected following ergosterol treatment.

Topics: Calcium; Calcium-Calmodulin-Dependent Protein Kinases; Calmodulin; Cyclopentanes; Disease Resistance; Ergosterol; Fungi; Gene Expression; Gene Expression Regulation, Plant; Genes, Plant; Nicotiana; Nitric Oxide; Oxylipins; Plant Diseases; Plant Proteins; Reactive Oxygen Species; Salicylic Acid; Signal Transduction; Spermine

Plants have developed general and specific defense mechanisms for protection against various enemies. Among the general defenses, induced resistance has distinct characteristics, such as broad-spectrum resistance and long-lasting effectiveness. This study evaluated over 500 specific chemical compounds derived from native Korean plant species to determine whether they triggered induced resistance against Pectobacterium carotovorum supsp. carotovorum (Pcc) in tobacco (Nicotiana tabacum) and Pseudomonas syringae pv. tomato (Pst) in Arabidopsis thaliana. To select target compound(s) with direct and indirect (volatile) effects, a new Petri-dish-based in vitro disease assay system with four compartments was developed. The screening assay showed that capsaicin, fisetin hydrate, jaceosidin, and farnesiferol A reduced the disease severity significantly in tobacco. Of these four compounds, capsaicin and jaceosidin induced resistance against Pcc and Pst, which depended on both salicylic acid (SA) and jasmonic acid (JA) signaling, using Arabidopsis transgenic and mutant lines, including npr1 and NahG for SA signaling and jar1 for JA signaling. The upregulation of the PR2 and PDF1.2 genes after Pst challenge with capsaicin pre-treatment indicated that SA and JA signaling were primed. These results demonstrate that capsaicin and jaceosidin can be effective triggers of strong induced resistance against both necrotrophic and biotrophic plant pathogens.

Topics: Arabidopsis; Capsaicin; Cyclopentanes; Disease Resistance; Flavonoids; Flavonols; Gene Expression Regulation, Plant; Genes, Plant; Host-Pathogen Interactions; Nicotiana; Oxylipins; Pectobacterium carotovorum; Plant Diseases; Plant Extracts; Plant Growth Regulators; Pseudomonas syringae; Republic of Korea; Salicylic Acid; Sesquiterpenes; Signal Transduction

Calcium-dependent protein kinases (CDPKs) are crucial calcium sensors involved in plant responses to pathogen infection. Here, we report isolation and functional characterization of the pathogen-responsive rice OsCPK10 gene. The expression of OsCPK10 was strongly induced following treatment with a Magnaporthe grisea elicitor. Kinase activity assay showed that the functional OsCPK10 protein not only autophosphorylated, but also phosphorylated Casein in a calcium-dependent manner. Overexpression of constitutively active OsCPK10 in Arabidopsis enhanced the resistance to infection with Pseudomonas syringae pv. tomato, associated with elevated expression of both SA- and JA-related defense genes. Similarly, transgenic rice plants containing constitutively active OsCPK10 exhibited enhanced resistance to blast fungus M. grisea. The enhanced resistance in the transgenic lines was associated with activated expression of SA- and JA-related defense genes. Collectively, our results indicate that rice OsCPK10 is a crucial regulator in plant immune responses, and that it may regulate disease resistance by activating both SA- and JA-dependent defense responses.

Topics: Amino Acid Sequence; Arabidopsis; Calcium-Binding Proteins; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Plant; Magnaporthe; Molecular Sequence Data; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Protein Serine-Threonine Kinases; Pseudomonas syringae; Salicylic Acid

Antimicrobial cationic peptides (AMPs) are ubiquitous small proteins used by living cells to defend against a wide spectrum of pathogens. Their amphipathic property helps their interaction with negatively charged cellular membrane of the pathogen causing cell lysis and death. AMPs also modulate signaling pathway(s) and cellular processes in animal models; however, little is known of cellular processes other than the pathogen-lysis phenomenon modulated by AMPs in plants. An engineered heterologous AMP, msrA3, expressed in potato was previously shown to cause resistance of the transgenic plants against selected fungal and bacterial pathogens. These lines together with the wild type were studied for growth habits, and for inducible defense responses during challenge with biotic (necrotroph Fusarium solani) and abiotic stressors (dark-induced senescence, wounding and temperature stress). msrA3-expression not only conferred protection against F. solani but also delayed development of floral buds and prolonged vegetative phase. Analysis of select gene transcript profiles showed that the transgenic potato plants were suppressed in the hypersensitive (HR) and reactive oxygen species (ROS) responses to both biotic and abiotic stressors. Also, the transgenic leaves accumulated lesser amounts of the defense hormone jasmonic acid upon wounding with only a slight change in salicylic acid as compared to the wild type. Thus, normal host defense responses to the pathogen and abiotic stressors were mitigated by msrA3 expression suggesting MSRA3 regulates a common step(s) of these response pathways. The stemming of the pathogen growth and mitigating stress response pathways likely contributes to resource reallocation for higher tuber yield.

Topics: Aging; Antimicrobial Cationic Peptides; Cyclopentanes; Disease Resistance; Flowers; Fusarium; Gene Expression; Gene Expression Regulation, Plant; Oxidative Stress; Oxylipins; Phenotype; Plants, Genetically Modified; Salicylic Acid; Solanum tuberosum

Complex plant defenses that include the hypersensitive response (HR) are mediated by plant hormones, such as salicylic acid (SA), jasmonic acid (JA) and ethylene. We previously isolated the Arabidopsis DEAR1 (DREB AND EAR MOTIF PROTEIN 1) regulator and showed that its overexpression DEAR1 (DEAR1ox) resulted in a dwarf phenotype and lesion-like cell death, accompanied by elevated expression of PR (PATHOGENESIS-RELATED) genes. Here, we show that transgenic Arabidopsis overexpressing DEAR1 (DEAR1ox) has enhanced resistance to the necrotrophic fungus Botrytis cinerea (B. cinerea). This result indicates that DEAR1 represses negative regulators of plant defense responses, including transcriptional repressors belonging to the ERF (ETHYLEN RESPONSE FACTOR) family. Knockout mutants of ERF9 (erf9), which were down-regulated in DEAR1ox plants, showed transcriptional promotion of PDF1.2 (PATHOGEN-INDUCIBLE PLANT DEFENSIN) genes, which serve as positive markers for the ethylene/jasmonic acid (JA) signaling pathway and provide enhanced resistance to B. cinerea. Biochemical assays demonstrated that the ERF9 in capable of binding to the GCC box, a cis-element contained in the promoters of the PDF1.2 gene that possesses trans-repression activity. Moreover, infection with B. cinerea resulted in the promotion of the PDF1.2 expression, coinciding with suppression of the ERF9 gene under the control of the DEAR1 gene. These results indicate that the transcriptional repressor ERF9 participates in plant defense mechanisms against necrotic fungi mediated by the DEAR1-dependent ethylene/JA signaling pathway.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cell Nucleus; Cyclopentanes; Defensins; Disease Resistance; Ethylenes; Gene Expression; Gene Expression Regulation, Plant; Gene Knockout Techniques; Models, Molecular; Oxylipins; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Promoter Regions, Genetic; Pseudomonas syringae; Salicylic Acid; Sequence Deletion; Signal Transduction; Transcription Factors

Boosted responsiveness of plant cells to stress at the onset of pathogen- or chemically induced resistance is called priming. The chemical β-aminobutyric acid (BABA) enhances Arabidopsis thaliana resistance to hemibiotrophic bacteria through the priming of the salicylic acid (SA) defence response. Whether BABA increases Arabidopsis resistance to the necrotrophic bacterium Pectobacterium carotovorum ssp. carotovorum (Pcc) is not clear. In this work, we show that treatment with BABA protects Arabidopsis against the soft-rot pathogen Pcc. BABA did not prime the expression of the jasmonate/ethylene-responsive gene PLANT DEFENSIN 1.2 (PDF1.2), the up-regulation of which is usually associated with resistance to necrotrophic pathogens. Expression of the SA marker gene PATHOGENESIS RELATED 1 (PR1) on Pcc infection was primed by BABA treatment, but SA-defective mutants demonstrated a wild-type level of BABA-induced resistance against Pcc. BABA primed the expression of the pattern-triggered immunity (PTI)-responsive genes FLG22-INDUCED RECEPTOR-LIKE KINASE 1 (FRK1), ARABIDOPSIS NON-RACE SPECIFIC DISEASE RESISTANCE GENE (NDR1)/HAIRPIN-INDUCED GENE (HIN1)-LIKE 10 (NHL10) and CYTOCHROME P450, FAMILY 81 (CYP81F2) after inoculation with Pcc or after treatment with purified bacterial microbe-associated molecular patterns, such as flg22 or elf26. PTI-mediated callose deposition was also potentiated in BABA-treated Arabidopsis, and BABA boosted Arabidopsis stomatal immunity to Pcc. BABA treatment primed the PTI response in the SA-defective mutants SA induction deficient 2-1 (sid2-1) and phytoalexin deficient 4-1 (pad4-1). In addition, BABA priming was associated with open chromatin configurations in the promoter region of PTI marker genes. Our data indicate that BABA primes the PTI response upon necrotrophic bacterial infection and suggest a role for the PTI response in BABA-induced resistance.

Topics: Aminobutyrates; Arabidopsis; Chromatin; Cyclopentanes; Disease Resistance; Ethylenes; Fungal Proteins; Gene Expression Regulation, Plant; Glucans; Histones; Models, Biological; Mutation; Oxylipins; Pectobacterium carotovorum; Plant Diseases; Plant Immunity; Plant Stomata; Receptors, Pattern Recognition; Salicylic Acid; Signal Transduction; Transcriptional Activation

WRKY proteins form a large family of plant transcription factors implicated in the modulation of numerous biological processes, such as growth, development and responses to various environmental stresses. However, the roles of the majority WRKY family members, especially in non-model plants, remain poorly understood. We identified CaWRKY40 from pepper. Transient expression in onion epidermal cells showed that CaWRKY40 can be targeted to nuclei and activates expression of a W-box-containing reporter gene. CaWRKY40 transcripts are induced in pepper by Ralstonia solanacearum and heat shock. To assess roles of CaWRKY40 in plant stress responses we performed gain- and loss-of-function experiments. Overexpression of CaWRKY40 enhanced resistance to R. solanacearum and tolerance to heat shock in tobacco. In contrast, silencing of CaWRKY40 enhanced susceptibility to R. solanacearum and impaired thermotolerance in pepper. Consistent with its role in multiple stress responses, we found CaWRKY40 transcripts to be induced by signalling mechanisms mediated by the stress hormones salicylic acid (SA), jasmonic acid (JA) and ethylene (ET). Overexpression of CaWRKY40 in tobacco modified the expression of hypersensitive response (HR)-associated and pathogenesis-related genes. Collectively, our results suggest that CaWRKY40 orthologs are regulated by SA, JA and ET signalling and coordinate responses to R. solanacearum attacks and heat stress in pepper and tobacco.

Topics: Capsicum; Cell Nucleus; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression; Gene Expression Regulation, Plant; Hot Temperature; Nicotiana; Onions; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Plant Proteins; Plants, Genetically Modified; Ralstonia solanacearum; Salicylic Acid; Seedlings; Sequence Analysis, DNA; Signal Transduction; Stress, Physiological; Transcription Factors

The role of defence gene expression triggered by Cd toxicity in the plant's response to Botrytis cinerea was investigated in Arabidopsis thaliana Columbia 0. Silicon (0 or 1.5 mM) and Cd (0, 1 or 10 μM) were supplied to 3-month-old solution-cultured plants. After 3 days, half of the plants of each treatment were inoculated with Botrytis. Supplied Cd concentrations were below the toxicity threshold and did not cause shoot growth inhibition or evidence of oxidative stress, while Botrytis infection severely decreased plant growth in all treatments. The expression of marker genes PR1 and BGL2 for the salicylic acid (SA) and the PDF1.2 for the jasmonic acid-ethylene (JA-ET) signalling pathways was enhanced in 10 μM Cd-treated non-infected plants. Twenty hours after inoculation, PDF1.2 expression showed a strong increase in all treatments, while enhanced PR1, BGL2, and CHIB expression was only found 7 days after infection. A great synergistic effect of Cd and Botrytis on PDF1.2 expression was found in 10 μM Cd-treated plants. Silicon decreased PR1, BGL2, and CHIB, while increasing PDF1.2 expression, which indicates its role as a modulator of the signalling pathways involved in the plant's response to fungal infection. Botrytis growth decreased in 10 μM Cd-treated plants, which could be due to the combined effects of Cd and Botrytis activating the SA and JA-ET-mediated signalling pathways. Taken together, our results provide support for the view that Cd concentrations close to the toxicity threshold induce defence signalling pathways which potentiate the plant's response against fungal infection.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Cadmium; Cyclopentanes; Defensins; Disease Resistance; Dose-Response Relationship, Drug; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Glucan Endo-1,3-beta-D-Glucosidase; Host-Pathogen Interactions; Oxylipins; Plant Diseases; Plant Leaves; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Signal Transduction; Silicon; Time Factors

Plants are subject to attack by a wide range of phytopathogens. Current pathogen detection methods and technologies are largely constrained to those occurring post-symptomatically. Recent efforts were made to generate plant sentinels (phytosensors) that can be used for sensing and reporting pathogen contamination in crops. Engineered phytosensors indicating the presence of plant pathogens as early-warning sentinels potentially have tremendous utility as wide-area detectors. We previously showed that synthetic promoters containing pathogen and/or defence signalling inducible cis-acting regulatory elements (RE) fused to a fluorescent protein (FP) reporter could detect phytopathogenic bacteria in a transient phytosensing system. Here, we further advanced this phytosensing system by developing stable transgenic tobacco and Arabidopsis plants containing candidate constructs. The inducibility of each synthetic promoter was examined in response to biotic (bacterial pathogens) or chemical (plant signal molecules salicylic acid, ethylene and methyl jasmonate) treatments using stably transgenic plants. The treated plants were visualized using epifluorescence microscopy and quantified using spectrofluorometry for FP synthesis upon induction. Time-course analyses of FP synthesis showed that both transgenic tobacco and Arabidopsis plants were capable to respond in predictable ways to pathogen and chemical treatments. These results provide insights into the potential applications of transgenic plants as phytosensors and the implementation of emerging technologies for monitoring plant disease outbreaks in agricultural fields.

Topics: Arabidopsis; Crops, Agricultural; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Bacterial; Genes, Plant; Genes, Reporter; Green Fluorescent Proteins; Host-Pathogen Interactions; Nicotiana; Oxylipins; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Promoter Regions, Genetic; Regulatory Elements, Transcriptional; Salicylic Acid; Transgenes

Exudation of benzoxazinoid metabolites from roots of young maize seedlings recruits the rhizobacterial strain Pseudomonas putida KT2440 from the soil to the rhizosphere. In this study, we have investigated whether these rhizobacteria are beneficial for maize by eliciting systemic defense priming. Root colonization of the maize hybrid cultivar Delprim by P. putida primed wound- and jasmonic acid (JA)-inducible emission of aromatic and terpenoid volatiles, but not the emission of the green leaf volatile (Z)-3-hexenyl acetate. Furthermore, root colonization by P. putida primed stress-inducible transcription of the JA-dependent gene SerPIN, whereas JA-dependent induction of the MPI gene was unaffected. Systemic priming of SerPIN by P. putida only occurred in benzoxazinoid-producing plants, and was absent in benzoxazinoid-deficient plants. The results from this study suggest that root colonization by P. putida primes a selection of JA-dependent defenses in Maize, which is reliant on benzoxazinoid exudation from the roots.

Topics: Benzoxazines; Cyclopentanes; Disease Resistance; Genes, Plant; Oxylipins; Plant Diseases; Plant Exudates; Plant Roots; Pseudomonas putida; Transcription, Genetic; Zea mays

In addition to basal defense mechanisms, plants are able to develop enhanced defense mechanisms such as induced resistance (IR) upon appropriate stimulation. We recently described the means by which several carboxylic acids protect Arabidopsis and tomato plants against fungi. In this work, we demonstrate the effectiveness of hexanoic acid (Hx) in the control of Alternaria brown spot (ABS) disease via enhancement of the immune system of Fortune mandarin. The application of 1mM Hx in irrigation water to 2-year-old Fortune plants clearly reduced the incidence of the disease and led to smaller lesions. We observed that several of the most important mechanisms involved in induced resistance were affected by Hx application. Our results demonstrate enhanced callose deposition in infected plants treated with Hx, which suggests an Hx priming mechanism. Plants treated with the callose inhibitor 2-DDG were more susceptible to the fungus. Moreover, polygalacturonase-inhibiting protein (PGIP) gene expression was rapidly and significantly upregulated in treated plants. However, treatment with Hx decreased the levels of reactive oxygen species (ROS) in infected plants. Hormonal and gene analyses revealed that the jasmonic acid (JA) pathway was activated due to a greater accumulation of 12-oxo-phytodienoic acid (OPDA) and JA along with a rapid accumulation of JA-isoleucine (JA-Ile). Furthermore, we observed a more rapid accumulation of abscisic acid (ABA), which could act as a positive regulator of callose deposition. Thus, our results support the hypothesis that both enhanced physical barriers and the JA signaling pathway are involved in hexanoic acid-induced resistance (Hx-IR) to Alternaria alternata.

Topics: Alternaria; Antifungal Agents; Caproates; Citrus; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Oxylipins; Plant Diseases; Plant Growth Regulators

Hexanoic acid-induced resistance (Hx-IR) is effective against several pathogens in tomato plants. Our study of the mechanisms implicated in Hx-IR against Pseudomonas syringae pv. tomato DC3000 suggests that hexanoic acid (Hx) treatment counteracts the negative effect of coronatine (COR) and jasmonyl-isoleucine (JA-Ile) on the salicylic acid (SA) pathway. In Hx-treated plants, an increase in the expression of jasmonic acid carboxyl methyltransferase (JMT) and the SA marker genes PR1 and PR5 indicates a boost in this signalling pathway at the expense of a decrease in JA-Ile. Moreover, Hx treatment potentiates 12-oxo-phytodienoic acid accumulation, which suggests that this molecule might play a role per se in Hx-IR. These results support a positive relationship between the SA and JA pathways in Hx-primed plants. Furthermore, one of the mechanisms of virulence mediated by COR is stomatal re-opening on infection with P. syringae. In this work, we observed that Hx seems to inhibit stomatal opening in planta in the presence of COR, which suggests that, on infection in tomato, this treatment suppresses effector action to prevent bacterial entry into the mesophyll.

Topics: Abscisic Acid; Amino Acids; Biosynthetic Pathways; Caproates; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucans; Indenes; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plant Stomata; Pseudomonas syringae; Salicylic Acid; Signal Transduction; Solanum lycopersicum; Water

Tomato Yellow Leaf Curl China virus spreads together with its invasive vector, the silverleaf whitefly B biotype, which exhibits higher growth rates on infected plants. Previous studies indicate that the virus satellite gene βC1 accounts for the visible symptoms of infection and inhibits the constitutive expression of jasmonic acid (JA)--a phytohormone involved in plant defense against whiteflies--and of some JA-regulated genes. Here we present new details of the effects of on plant signaling and defense, obtained with (non-host) transgenic Arabidopsis thaliana and Nicotiana benthamiana plants. We found that JA induction in response to wounding was reduced in plants expressing βC1. This result implies that βC1 acts on conserved plant regulation mechanisms and might impair the entire JA defense pathway. Furthermore, transformed N. benthamiana plants exhibited elevated emissions of the volatile compound linalool, suggesting that βC1 also influences plant-derived olfactory cues available to vector and non-vector insects.

Topics: Acyclic Monoterpenes; Animals; Arabidopsis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Genes, Viral; Hemiptera; Herbivory; Monoterpenes; Nicotiana; Oils, Volatile; Oxylipins; Plant Diseases; Plants, Genetically Modified; Satellite Viruses; Signal Transduction; Solanum lycopersicum

A common response by plants to fungal attack is deposition of callose, a (1,3)-β-glucan polymer, in the form of cell wall thickenings called papillae, at site of wall penetration. While it has been generally believed that the papillae provide a structural barrier to slow fungal penetration, this idea has been challenged in recent studies of Arabidopsis (Arabidopsis thaliana), where fungal resistance was found to be independent of callose deposition. To the contrary, we show that callose can strongly support penetration resistance when deposited in elevated amounts at early time points of infection. We generated transgenic Arabidopsis lines that express POWDERY MILDEW RESISTANT4 (PMR4), which encodes a stress-induced callose synthase, under the control of the constitutive 35S promoter. In these lines, we detected callose synthase activity that was four times higher than that in wild-type plants 6 h post inoculation with the virulent powdery mildew Golovinomyces cichoracearum. The callose synthase activity was correlated with enlarged callose deposits and the focal accumulation of green fluorescent protein-tagged PMR4 at sites of attempted fungal penetration. We observed similar results from infection studies with the nonadapted powdery mildew Blumeria graminis f. sp. hordei. Haustoria formation was prevented in resistant transgenic lines during both types of powdery mildew infection, and neither the salicylic acid-dependent nor jasmonate-dependent pathways were induced. We present a schematic model that highlights the differences in callose deposition between the resistant transgenic lines and the susceptible wild-type plants during compatible and incompatible interactions between Arabidopsis and powdery mildew.

Topics: Adaptation, Physiological; Arabidopsis; Arabidopsis Proteins; Ascomycota; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Glucans; Green Fluorescent Proteins; Models, Biological; Oxylipins; Phenotype; Plant Diseases; Plants, Genetically Modified; Salicylic Acid; Time Factors; Transcription, Genetic

Resistance to biotrophic pathogens is largely dependent on the hormone salicylic acid (SA) while jasmonic acid (JA) regulates resistance against necrotrophs. JA negatively regulates SA and is, in itself, negatively regulated by SA. A key component of the JA signal transduction pathway is its receptor, the COI1 gene. Mutations in this gene can affect all the JA phenotypes, whereas mutations in other genes, either in JA signal transduction or in JA biosynthesis, lack this general effect. To identify components of the part of the resistance against biotrophs independent of SA, a mutagenised population of NahG plants (severely depleted of SA) was screened for suppression of susceptibility. The screen resulted in the identification of intragenic and extragenic suppressors, and the results presented here correspond to the characterization of one extragenic suppressor, coi1-40. coi1-40 is quite different from previously described coi1 alleles, and it represents a strategy for enhancing resistance to biotrophs with low levels of SA, likely suppressing NahG by increasing the perception to the remaining SA. The phenotypes of coi1-40 lead us to speculate about a modular function for COI1, since we have recovered a mutation in COI1 which has a number of JA-related phenotypes reduced while others are equal to or above wild type levels.

Topics: Alleles; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; DNA-Binding Proteins; Fertility; Gene Expression Regulation, Plant; Mutagenesis; Oxylipins; Phenotype; Pseudomonas putida; Transcription Factors

Pseudozyma spp. are yeast-like fungi, classified in the Ustilaginales, which are mostly epiphytic or saprophytic and are not pathogenic to plants. Several Pseudozyma species have been reported to exhibit biological activity against powdery mildews. However, previous studies have reported that Pseudozyma aphidis, which can colonize plant surfaces, is not associated with the collapse of powdery mildew colonies. In this report, we describe a novel P. aphidis strain and study its interactions with its plant host and the plant pathogen Botrytis cinerea. This isolate was found to secrete extracellular metabolites that inhibit various fungal pathogens in vitro and significantly reduce B. cinerea infection in vivo. Moreover, P. aphidis sensitized Arabidopsis (Arabidopsis thaliana) plants' defense machinery via local and systemic induction of pathogenesis-related1 (PR1) and plant defensin1.2 (PDF1.2) expression. P. aphidis also reduced B. cinerea infection, locally and systemically, in Arabidopsis mutants impaired in jasmonic acid (JA) or salicylic acid (SA) signaling. Thus, in addition to direct inhibition, P. aphidis may inhibit B. cinerea infection via induced resistance in a manner independent of SA, JA, and Nonexpressor of PR1 (NPR1). P. aphidis primed the plant defense machinery and induced stronger activation of PDF1.2 after B. cinerea infection. Finally, P. aphidis fully or partially reconstituted PR1 and PDF1.2 expression in npr1-1 mutant and in plants with the SA hydroxylase NahG transgene, but not in a jasmonate resistant1-1 mutant, after B. cinerea infection, suggesting that P. aphidis can bypass the SA/NPR1, but not JA, pathway to activate PR genes. Thus, either partial gene activation is sufficient to induce resistance, or the resistance is not directed solely through PR1 and PDF1.2 but probably through other pathogen-resistance genes or pathways as well.

Topics: Arabidopsis; Arabidopsis Proteins; Basidiomycota; Botrytis; Cyclopentanes; Disease Resistance; Microbial Interactions; Mutation; Oxylipins; Pest Control, Biological; Plant Diseases; Plant Leaves; Salicylic Acid; Solanum lycopersicum

Powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating disease of wheat. The use of wheat cultivars resistant to powdery mildew provides an effective, economical, and environmentally friendly method to control the disease. Previously, we identified a dominant resistance gene, temporarily named Pmhym, from the wheat cultivar Hongyoumai. In order to screen differential transcripts related to Pmhym-mediated resistance, four F3 homozygous resistant and four susceptible progenies derived from the Hongyoumai/Yumai13 cross were selected to construct two different pools, respectively, representing an incompatible and compatible interaction with Bgt. Pre-inoculated control and the pathogen-inoculated treatments at 24 h post inoculation (hpi) were used. Three groups of differential genes were categorized from three comparisons as pre- and post-induced, respectively, in two interactions, and post-induced between incompatible and compatible interaction. It was found that salicylic acid (SA), jasmonate (JA), and ethylene (ET) signaling-related genes were differentially expressed, thus suggesting that they are involved in the defensive response against Bgt infection. In compatible interactions, the genes involved in the abscisic acid (ABA) signaling pathway might be inhibitory to the above-mentioned three pathways, resulting in a susceptible reaction. Genes involved in disease/defense, signal transduction, and reactive oxygen species (ROS) metabolism were up-regulated in incompatible interactions, implying a role in resistant response. The results of qRT-PCR analysis on several candidate genes were consistent in their expression patterns as revealed by microarray analysis. The differential expression analyses in the present study are good candidates for further elucidation of wheat defensive response to powdery mildew.

Topics: Ascomycota; Crosses, Genetic; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Intracellular Signaling Peptides and Proteins; Oligonucleotide Array Sequence Analysis; Oxylipins; Plant Diseases; Reverse Transcriptase Polymerase Chain Reaction; Salicylic Acid; Triticum

Bacterial leaf streak of rice (BLS) caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a widely-spread disease in the main rice-producing areas of the world. Investigating the genes that play roles in rice-Xoc interactions helps us to understand the defense signaling pathway in rice. Here we report a differentially expressed protein gene (DEPG1), which regulates susceptibility to BLS. DEPG1 is a nucleotide-binding site (NBS)-leucine rich repeat (LRR) gene, and the deduced protein sequence of DEPG1 has approximately 64% identity with that of the disease resistance gene Pi37. Phylogenetic analysis of DEPG1 and the 18 characterized NBS-LRR genes revealed that DEPG1 is more closely related to Pi37. DEPG1 protein is located to the cytoplasm, which was confirmed by transient expression of DEPG1-GFP (green fluorescent protein) fusion construct in onion epidermal cells. Semi-quantitative PCR assays showed that DEPG1 is widely expressed in rice, and is preferentially expressed in internodes, leaf blades, leaf sheaths and flag leaves. Observation of cross sections of leaves from the transgenic plants with a DEPG1-promoter::glucuronidase (GUS) fusion gene revealed that DEPG1 is also highly expressed in mesophyll tissues where Xoc mainly colonizes. Additionally, Xoc negatively regulates expression of DEPG1 at the early stage of the pathogen infection, and so do the three defense-signal compounds including salicylic acid (SA), methyl jasmonate (MeJA) and 1-aminocyclopropane-1-carboxylic-acid (ACC). Transgenic rice plants overexpressing DEPG1 exhibit enhanced susceptibility to Xoc compared to the wild-type controls. Moreover, enhanced susceptibility to Xoc may be mediated by inhibition of the expression of some SA biosynthesis-related genes and pathogenesis-related genes that may contribute to the disease resistance. Taken together, DEPG1 plays roles in the interactions between rice and BLS pathogen Xoc.

Topics: Amino Acid Sequence; Cyclopentanes; Disease Resistance; DNA, Plant; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Leucine-Rich Repeat Proteins; Molecular Sequence Data; Nucleotides; Onions; Organ Specificity; Oryza; Oxylipins; Phylogeny; Plant Diseases; Plant Epidermis; Plant Proteins; Plants, Genetically Modified; Proteins; Salicylic Acid; Subcellular Fractions; Xanthomonas

• Priming of defence is a strategy employed by plants exposed to stress to enhance resistance against future stress episodes with minimal associated costs on growth. Here, we test the hypothesis that application of priming agents to seeds can result in plants with primed defences. • We measured resistance to arthropod herbivores and disease in tomato (Solanum lycopersicum) plants grown from seed treated with jasmonic acid (JA) and/or β-aminobutryric acid (BABA). • Plants grown from JA-treated seed showed increased resistance against herbivory by spider mites, caterpillars and aphids, and against the necrotrophic fungal pathogen, Botrytis cinerea. BABA seed treatment provided primed defence against powdery mildew disease caused by the biotrophic fungal pathogen, Oidium neolycopersici. Priming responses were long-lasting, with significant increases in resistance sustained in plants grown from treated seed for at least 8 wk, and were associated with enhanced defence gene expression during pathogen attack. There was no significant antagonism between different forms of defence in plants grown from seeds treated with a combination of JA and BABA. • Long-term defence priming by seed treatments was not accompanied by reductions in growth, and may therefore be suitable for commercial exploitation.

Topics: Abscisic Acid; Aminobutyrates; Animals; Aphids; Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Herbivory; Manduca; Oxylipins; Plant Diseases; Seeds; Signal Transduction; Solanum lycopersicum; Tetranychidae; Transcription, Genetic

We report here that disruption of function of the ω-3 FATTY ACID DESATURASE7 (FAD7) enhances plant defenses against aphids. The suppressor of prosystemin-mediated responses2 (spr2) mutation in tomato (Solanum lycopersicum), which eliminates the function of FAD7, reduces the settling behavior, survival, and fecundity of the potato aphid (Macrosiphum euphorbiae). Likewise, the antisense suppression of LeFAD7 expression in wild-type tomato plants reduces aphid infestations. Aphid resistance in the spr2 mutant is associated with enhanced levels of salicylic acid (SA) and mRNA encoding the pathogenesis-related protein P4. Introduction of the Naphthalene/salicylate hydroxylase transgene, which suppresses SA accumulation, restores wild-type levels of aphid susceptibility to spr2. Resistance in spr2 is also lost when we utilize virus-induced gene silencing to suppress the expression of NONEXPRESSOR OF PATHOGENESIS-RELATED PROTEINS1 (NPR1), a positive regulator of many SA-dependent defenses. These results indicate that FAD7 suppresses defenses against aphids that are mediated through SA and NPR1. Although loss of function of FAD7 also inhibits the synthesis of jasmonate (JA), the effects of this desaturase on aphid resistance are not dependent on JA; other mutants impaired in JA synthesis (acx1) or perception (jai1-1) show wild-type levels of aphid susceptibility, and spr2 retains aphid resistance when treated with methyl jasmonate. Thus, FAD7 may influence JA-dependent defenses against chewing insects and SA-dependent defenses against aphids through independent effects on JA synthesis and SA signaling. The Arabidopsis (Arabidopsis thaliana) mutants Atfad7-2 and Atfad7-1fad8 also show enhanced resistance to the green peach aphid (Myzus persicae) compared with wild-type controls, indicating that FAD7 influences plant-aphid interactions in at least two plant families.

Topics: Acetates; Animals; Aphids; Arabidopsis; Biosynthetic Pathways; Cyclopentanes; Disease Resistance; Fatty Acid Desaturases; Feeding Behavior; Fertility; Gene Expression Regulation, Plant; Genes, Plant; Mutation; Oxylipins; Plant Diseases; Plant Proteins; Salicylic Acid; Solanum lycopersicum; Survival Analysis; Transgenes; Up-Regulation

S-Nitrosoglutathione (GSNO) is a bioactive, stable, and mobile reservoir of nitric oxide (NO), and an important player in defence responses to herbivory and pathogen attack in plants. It has been demonstrated previously that GSNO reductase (GSNOR) is the main enzyme responsible for the in vivo control of intracellular levels of GSNO. In this study, the role of S-nitrosothiols, in particular of GSNO, in systemic defence responses in Arabidopsis thaliana was investigated further. It was shown that GSNO levels increased rapidly and uniformly in injured Arabidopsis leaves, whereas in systemic leaves GSNO was first detected in vascular tissues and later spread over the parenchyma, suggesting that GSNO is involved in the transmission of the wound mobile signal through the vascular tissue. Moreover, GSNO accumulation was required to activate the jasmonic acid (JA)-dependent wound responses, whereas the alternative JA-independent wound-signalling pathway did not involve GSNO. Furthermore, extending previous work on the role of GSNOR in pathogenesis, it was shown that GSNO acts synergistically with salicylic acid in systemic acquired resistance activation. In conclusion, GSNOR appears to be a key regulator of systemic defence responses, in both wounding and pathogenesis.

Topics: Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glutathione Reductase; Oxylipins; Plant Leaves; Plants, Genetically Modified; S-Nitrosoglutathione; S-Nitrosothiols; Salicylic Acid

Light is an important modulator of plant immune responses. Here, we show that inactivation of the photoreceptor phytochrome B (phyB) by a low red/far-red ratio (R:FR), which is a signal of competition in plant canopies, down-regulates the expression of defense markers induced by the necrotrophic fungus Botrytis cinerea, including the genes that encode the transcription factor ETHYLENE RESPONSE FACTOR1 (ERF1) and the plant defensin PLANT DEFENSIN1.2 (PDF1.2). This effect of low R:FR correlated with a reduced sensitivity to jasmonate (JA), thus resembling the antagonistic effects of salicylic acid (SA) on JA responses. Low R:FR failed to depress PDF1.2 mRNA levels in a transgenic line in which PDF1.2 transcription was up-regulated by constitutive expression of ERF1 in a coronatine insensitive1 (coi1) mutant background (35S::ERF1/coi1). These results suggest that the low R:FR effect, in contrast to the SA effect, requires a functional SCFCOI1-JASMONATE ZIM-DOMAIN (JAZ) JA receptor module. Furthermore, the effect of low R:FR depressing the JA response was conserved in mutants impaired in SA signaling (sid2-1 and npr1-1). Plant exposure to low R:FR ratios and the phyB mutation markedly increased plant susceptibility to B. cinerea; the effect of low R:FR was (1) independent of the activation of the shade-avoidance syndrome, (2) conserved in the sid2-1 and npr1-1 mutants, and (3) absent in two RNA interference lines disrupted for the expression of the JAZ10 gene. Collectively, our results suggest that low R:FR ratios depress Arabidopsis (Arabidopsis thaliana) immune responses against necrotrophic microorganisms via a SA-independent mechanism that requires the JAZ10 transcriptional repressor and that this effect may increase plant susceptibility to fungal infection in dense canopies.

Topics: Anthocyanins; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Down-Regulation; Gene Expression Regulation, Plant; Genes, Plant; Light; Mutation; Nuclear Proteins; Oxylipins; Phenols; Phenotype; Phytochrome B; Plant Diseases; Salicylic Acid; Signal Transduction

The Arabidopsis (Arabidopsis thaliana) transcription factor WRKY33 is essential for defense toward the necrotrophic fungus Botrytis cinerea. Here, we aimed at identifying early transcriptional responses mediated by WRKY33. Global expression profiling on susceptible wrky33 and resistant wild-type plants uncovered massive differential transcriptional reprogramming upon B. cinerea infection. Subsequent detailed kinetic analyses revealed that loss of WRKY33 function results in inappropriate activation of the salicylic acid (SA)-related host response and elevated SA levels post infection and in the down-regulation of jasmonic acid (JA)-associated responses at later stages. This down-regulation appears to involve direct activation of several jasmonate ZIM-domain genes, encoding repressors of the JA-response pathway, by loss of WRKY33 function and by additional SA-dependent WRKY factors. Moreover, genes involved in redox homeostasis, SA signaling, ethylene-JA-mediated cross-communication, and camalexin biosynthesis were identified as direct targets of WRKY33. Genetic studies indicate that although SA-mediated repression of the JA pathway may contribute to the susceptibility of wrky33 plants to B. cinerea, it is insufficient for WRKY33-mediated resistance. Thus, WRKY33 apparently directly targets other still unidentified components that are also critical for establishing full resistance toward this necrotroph.

Topics: Agrobacterium tumefaciens; Arabidopsis; Arabidopsis Proteins; Botrytis; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Indoles; Oxidation-Reduction; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Leaves; Promoter Regions, Genetic; Salicylic Acid; Signal Transduction; Thiazoles; Transcription Factors; Transcription, Genetic; Transformation, Genetic

Phosphite (Phi), a phloem-mobile oxyanion of phosphorous acid (H(3)PO(3)), protects plants against diseases caused by oomycetes. Its mode of action is unclear, as evidence indicates both direct antibiotic effects on pathogens as well as inhibition through enhanced plant defense responses, and its target(s) in the plants is unknown. Here, we demonstrate that the biotrophic oomycete Hyaloperonospora arabidopsidis (Hpa) exhibits an unusual biphasic dose-dependent response to Phi after inoculation of Arabidopsis (Arabidopsis thaliana), with characteristics of indirect activity at low doses (10 mm or less) and direct inhibition at high doses (50 mm or greater). The effect of low doses of Phi on Hpa infection was nullified in salicylic acid (SA)-defective plants (sid2-1, NahG) and in a mutant impaired in SA signaling (npr1-1). Compromised jasmonate (jar1-1) and ethylene (ein2-1) signaling or abscisic acid (aba1-5) biosynthesis, reactive oxygen generation (atrbohD), or accumulation of the phytoalexins camalexin (pad3-1) and scopoletin (f6'h1-1) did not affect Phi activity. Low doses of Phi primed the accumulation of SA and Pathogenesis-Related protein1 transcripts and mobilized two essential components of basal resistance, Enhanced Disease Susceptibility1 and Phytoalexin Deficient4, following pathogen challenge. Compared with inoculated, Phi-untreated plants, the gene expression, accumulation, and phosphorylation of the mitogen-activated protein kinase MPK4, a negative regulator of SA-dependent defenses, were reduced in plants treated with low doses of Phi. We propose that Phi negatively regulates MPK4, thus priming SA-dependent defense responses following Hpa infection.

Topics: Abscisic Acid; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; DNA-Binding Proteins; Dose-Response Relationship, Drug; Ethylenes; Gene Expression Regulation, Plant; Indoles; Mitogen-Activated Protein Kinases; Oomycetes; Oxylipins; Phosphites; Phosphorylation; Plant Diseases; Plant Immunity; Salicylic Acid; Scopoletin; Signal Transduction; Thiazoles

Light is emerging as a central regulator of plant immune responses against herbivores and pathogens. Solar UV-B radiation plays an important role as a positive modulator of plant defense. However, since UV-B photons can interact with a wide spectrum of molecular targets in plant tissues, the mechanisms that mediate their effects on plant defense have remained elusive. Here, we show that ecologically meaningful doses of UV-B radiation increase Arabidopsis resistance to the necrotrophic fungus Botrytis cinerea and that this effect is mediated by the photoreceptor UVR8. The UV-B effect on plant resistance was conserved in mutants impaired in jasmonate (JA) signaling (jar1-1 and P35S:JAZ10.4) or metabolism of tryptophan-derived defense compounds (pen2-1, pad3-1, pen2 pad3), suggesting that neither regulation of the JA pathway nor changes in levels of indolic glucosinolates (iGS) or camalexin are involved in this response. UV-B radiation, acting through UVR8, increased the levels of flavonoids and sinapates in leaf tissue. The UV-B effect on pathogen resistance was still detectable in tt4-1, a mutant deficient in chalcone synthase and therefore impaired in the synthesis of flavonoids, but was absent in fah1-7, a mutant deficient in ferulic acid 5-hydroxylase, which is essential for sinapate biosynthesis. Collectively, these results indicate that UVR8 plays an important role in mediating the effects of UV-B radiation on pathogen resistance by controlling the expression of the sinapate biosynthetic pathway.

Topics: Arabidopsis; Arabidopsis Proteins; Botrytis; Chromosomal Proteins, Non-Histone; Coumaric Acids; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucosinolates; Indoles; Mutation; Oxylipins; Phenols; Plant Diseases; Signal Transduction; Thiazoles; Ultraviolet Rays

Elevation in atmospheric CO(2) concentration broadly affects plant phenology and physiology, and these effects may alter the performance of plant viruses. The effects of elevated CO(2) on the susceptibility of tomato plants to Tomato yellow leaf curl virus (TYLCV) were examined for two successive years in open top chambers (OTC) in the field. We experimentally tested the hypothesis that elevated CO(2) would reduce the incidence and severity of TYLCV on tomato by altering plant defence strategies. Our results showed that elevated CO(2) decreased TYLCV disease incidence (by 14.6% in 2009 and 11.8% in 2010) and decreased disease severity (by 20.0% in 2009 and 10.4% in 2010). Elevated CO(2) also decreased the level of TYLCV coat protein in tomato leaves. Regardless of virus infection, elevated CO(2) increased plant height and aboveground biomass. Additionally, elevated CO(2) increased the leaf C:N ratio of tomato, but decreased soluble protein content in leaves. Notably, elevated CO(2) increased the salicylic acid (SA) level in uninfected and infected plants. In contrast, elevated CO(2) reduced jasmonic acid (JA) in uninfected plants while it increased JA and abscisic acid (ABA) in virus-infected plants. Furthermore, combined exogenous SA and JA application enhanced resistance to TYLCV more than application of either SA or JA alone. Our results suggest that the modulated antagonistic relationship between SA and JA under elevated CO(2) makes a great contribution to increased tomato resistance to TYLCV, and the predicted increases in tomato productivity may be enhanced by reduced plant virus susceptibility under projected rising CO(2) conditions.

Topics: Abscisic Acid; Capsid Proteins; Carbon Dioxide; Cyclopentanes; Disease Resistance; Oxylipins; Plant Diseases; Plant Leaves; Plant Stems; Plant Viruses; Salicylic Acid; Solanum lycopersicum

Plants perceive endogenous molecules or their fragments as signals of danger when these appear at increased concentrations in the extracellular space, and they respond with increased endogenous levels of jasmonic acid. The wound hormone jasmonic acid represents a central player in the induced resistance of plants to herbivore feeding and infection by necrotrophic pathogens. This 'damaged self recognition' mechanism of plants exhibits astonishing similarities to the perception of 'damage-associated molecular patterns' (DAMPs) by the human immune system: endogenous cell constituents, or their fragments, that can be released into the extracellular milieu during states of cellular stress or damage function as 'stress signals' and trigger inflammatory and other immunity-related responses. Multicellular organisms use endogenous molecules as danger signals to mount adequate healing and resistance-related responses without depending on exogenous signals and to place exogenous, enemy-derived molecular signals into the adequate functional context.

Topics: Animals; Cyclopentanes; Disease Resistance; Extracellular Matrix; Immunologic Factors; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Signal Transduction; Stress, Physiological

Here, multiple functions of jasmonic acid (JA) in maize (Zea mays) are revealed by comprehensive analyses of JA-deficient mutants of the two oxo-phytodienoate reductase genes, OPR7 and OPR8. Single mutants produce wild-type levels of JA in most tissues, but the double mutant opr7 opr8 has dramatically reduced JA in all organs tested. opr7 opr8 displayed strong developmental defects, including formation of a feminized tassel, initiation of female reproductive buds at each node, and extreme elongation of ear shanks; these defects were rescued by exogenous JA. These data provide evidence that JA is required for male sex determination and suppression of female reproductive organ biogenesis. Moreover, opr7 opr8 exhibited delayed leaf senescence accompanied by reduced ethylene and abscisic acid levels and lack of anthocyanin pigmentation of brace roots. Remarkably, opr7 opr8 is nonviable in nonsterile soil and under field conditions due to extreme susceptibility to a root-rotting oomycete (Pythium spp), demonstrating that these genes are necessary for maize survival in nature. Supporting the importance of JA in insect defense, opr7 opr8 is susceptible to beet armyworm. Overall, this study provides strong genetic evidence for the global roles of JA in maize development and immunity to pathogens and insects.

Topics: Alleles; Animals; Anthocyanins; Cyclopentanes; Disease Resistance; DNA Transposable Elements; Genes, Plant; Herbivory; Mutagenesis, Insertional; Mutation; Organ Specificity; Oxylipins; Phenotype; Pigmentation; Plant Diseases; Plant Leaves; Plant Proteins; Plant Shoots; Pythium; Spodoptera; Zea mays

Although an important oil crop, peanut has only 162,030 expressed sequence tags (ESTs) publicly available, 86,943 of which are from cultivated plants. More ESTs from cultivated peanuts are needed for isolation of stress-resistant, tissue-specific and developmentally important genes. Here, we generated 63,234 ESTs from our 5 constructed peanut cDNA libraries of Ralstonia solanacearum challenged roots, R. solanacearum challenged leaves, and unchallenged cultured peanut roots, leaves and developing seeds. Among these ESTs, there were 14,547 unique sequences with 7,961 tentative consensus sequences and 6,586 singletons. Putative functions for 47.8 % of the sequences were identified, including transcription factors, tissue-specific genes, genes involved in fatty acid biosynthesis and oil formation regulation, and resistance gene analogue genes. Additionally, differentially expressed genes, including those involved in ethylene and jasmonic acid signal transduction pathways, from both peanut leaves and roots, were identified in R. solanacearum challenged samples. This large expression dataset from different peanut tissues will be a valuable source for marker development and gene expression analysis. It will also be helpful for finding candidate genes for fatty acid synthesis and oil formation regulation as well as for studying mechanisms of interactions between the peanut host and R. solanacearum pathogen.

Topics: Arachis; Consensus Sequence; Crops, Agricultural; Cyclopentanes; Disease Resistance; Ethylenes; Expressed Sequence Tags; Fatty Acids; Gene Expression Regulation, Plant; Gene Library; Genes, Plant; Genes, Regulator; Oxylipins; Plant Diseases; Plant Leaves; Plant Oils; Plant Proteins; Plant Roots; Ralstonia solanacearum; Seeds; Signal Transduction; Transcription Factors

Class III peroxidases (Prxs) are enzymes involved in a multitude of physiological and stress-related processes in plants. Here, we report on the characterization of a putative peroxidase-encoding gene from Coffea arabica (CaPrx) that is expressed in early stages of root-knot nematode (RKN) infection. CaPrx showed enhanced expression in coffee roots inoculated with RKN (at 12 h post-inoculation), but no significant difference in expression was observed between susceptible and resistant plants. Assays using transgenic tobacco plants harboring a promoter-β-glucuronidase (GUS) fusion revealed that the CaPrx promoter was exclusively active in the galls induced by RKN. In cross sections of galls, GUS staining was predominantly localized in giant cells. Up-regulation of GUS expression in roots of transgenic plants following RKN inoculation was observed within 16 h. Moreover, no increase in GUS expression after treatment with jasmonic acid was detected. Altogether, these results point to a putative role of this peroxidase in the general coffee response to RKN infection.

Topics: Animals; Base Sequence; Coffea; Cyclopentanes; Disease Resistance; DNA, Complementary; Expressed Sequence Tags; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Genes, Plant; Genes, Reporter; Glucuronidase; Molecular Sequence Data; Nicotiana; Organ Specificity; Oxylipins; Peroxidases; Phylogeny; Plant Diseases; Plant Proteins; Plant Roots; Plants, Genetically Modified; Promoter Regions, Genetic; Reproducibility of Results; Tylenchoidea

WRKY transcription factors are crucial regulatory components of plant responses to pathogen infection. In the present study, we report isolation and functional characterization of the pathogen-responsive rice WRKY30 gene, whose transcripts accumulate rapidly in response to salicylic acid (SA) and jasmonic acid (JA) treatment. Overexpression of WRKY30 in rice enhanced resistance to rice sheath blight fungus Rhizoctonia solani and blast fungus Magnaporthe grisea. The enhanced resistance in the transgenic lines overexpressing WRKY30 was associated with activated expression of JA synthesis-related genes LOX, AOS2 and pathogenesis-related (PR)3 and PR10, and increased endogenous JA accumulation under the challenge of fungal pathogens. WRKY30 was nuclear-localized and had transcriptional activation ability in yeast cells, supporting that it functions as a transcription factor. Together, our findings indicate that JA plays a crucial role in the WRKY30-mediated defense responses to fungal pathogens, and that the rice WRKY30 seems promising as an important candidate gene to improve disease resistance in rice.

Topics: Cell Nucleus; Cyclopentanes; Disease Resistance; DNA, Complementary; Gene Expression Regulation, Plant; Magnaporthe; Oryza; Oxylipins; Plant Diseases; Plant Proteins; Plants, Genetically Modified; Rhizoctonia; Salicylic Acid; Transcriptional Activation; Yeasts

Plant resistance to phytopathogenic microorganisms mainly relies on the activation of an innate immune response usually launched after recognition by the plant cells of microbe-associated molecular patterns. The plant hormones, salicylic acid (SA), jasmonic acid, and ethylene have emerged as key players in the signaling networks involved in plant immunity. Rhamnolipids (RLs) are glycolipids produced by bacteria and are involved in surface motility and biofilm development. Here we report that RLs trigger an immune response in Arabidopsis (Arabidopsis thaliana) characterized by signaling molecules accumulation and defense gene activation. This immune response participates to resistance against the hemibiotrophic bacterium Pseudomonas syringae pv tomato, the biotrophic oomycete Hyaloperonospora arabidopsidis, and the necrotrophic fungus Botrytis cinerea. We show that RL-mediated resistance involves different signaling pathways that depend on the type of pathogen. Ethylene is involved in RL-induced resistance to H. arabidopsidis and to P. syringae pv tomato whereas jasmonic acid is essential for the resistance to B. cinerea. SA participates to the restriction of all pathogens. We also show evidence that SA-dependent plant defenses are potentiated by RLs following challenge by B. cinerea or P. syringae pv tomato. These results highlight a central role for SA in RL-mediated resistance. In addition to the activation of plant defense responses, antimicrobial properties of RLs are thought to participate in the protection against the fungus and the oomycete. Our data highlight the intricate mechanisms involved in plant protection triggered by a new type of molecule that can be perceived by plant cells and that can also act directly onto pathogens.

Topics: Arabidopsis; Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Glycolipids; Models, Biological; Mutation; Oxylipins; Peronospora; Plant Diseases; Plant Leaves; Pseudomonas syringae; Salicylic Acid; Signal Transduction; Spores, Bacterial; Spores, Fungal

Plant resistance to necrotrophic fungi is regulated by a complex set of signaling pathways that includes those mediated by the hormones salicylic acid (SA), ethylene (ET), jasmonic acid (JA), and abscisic acid (ABA). The role of ABA in plant resistance remains controversial, as positive and negative regulatory functions have been described depending on the plant-pathogen interaction analyzed. Here, we show that ABA signaling negatively regulates Arabidopsis (Arabidopsis thaliana) resistance to the necrotrophic fungus Plectosphaerella cucumerina. Arabidopsis plants impaired in ABA biosynthesis, such as the aba1-6 mutant, or in ABA signaling, like the quadruple pyr/pyl mutant (pyr1pyl1pyl2pyl4), were more resistant to P. cucumerina than wild-type plants. In contrast, the hab1-1abi1-2abi2-2 mutant impaired in three phosphatases that negatively regulate ABA signaling displayed an enhanced susceptibility phenotype to this fungus. Comparative transcriptomic analyses of aba1-6 and wild-type plants revealed that the ABA pathway negatively regulates defense genes, many of which are controlled by the SA, JA, or ET pathway. In line with these data, we found that aba1-6 resistance to P. cucumerina was partially compromised when the SA, JA, or ET pathway was disrupted in this mutant. Additionally, in the aba1-6 plants, some genes encoding cell wall-related proteins were misregulated. Fourier transform infrared spectroscopy and biochemical analyses of cell walls from aba1-6 and wild-type plants revealed significant differences in their Fourier transform infrared spectratypes and uronic acid and cellulose contents. All these data suggest that ABA signaling has a complex function in Arabidopsis basal resistance, negatively regulating SA/JA/ET-mediated resistance to necrotrophic fungi.

Topics: Abscisic Acid; Arabidopsis; Ascomycota; Cell Wall; Cluster Analysis; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Models, Biological; Mutation; Oxylipins; Plant Diseases; Plant Growth Regulators; Salicylic Acid; Signal Transduction; Spectroscopy, Fourier Transform Infrared; Stress, Physiological

Systemic acquired resistance (SAR) is a long-lasting plant immunity against a broad spectrum of pathogens. Biological induction of SAR requires the signal molecule salicylic acid (SA) and involves profound transcriptional changes that are largely controlled by the transcription coactivator nonexpressor of pathogenesis-related genes1 (NPR1). However, it is unclear how SAR signals are transduced from the NPR1 signaling node to the general transcription machinery. Here, we report that the Arabidopsis thaliana Mediator subunit16 (MED16) is an essential positive regulator of SAR. Mutations in MED16 reduced NPR1 protein levels and completely compromised biological induction of SAR. These mutations also significantly suppressed SA-induced defense responses, altered the transcriptional changes induced by the avirulent bacterial pathogen Pseudomonas syringae pv tomato (Pst) DC3000/avrRpt2, and rendered plants susceptible to both Pst DC3000/avrRpt2 and Pst DC3000. In addition, mutations in MED16 blocked the induction of several jasmonic acid (JA)/ethylene (ET)-responsive genes and compromised resistance to the necrotrophic fungal pathogens Botrytis cinerea and Alternaria brassicicola. The Mediator complex acts as a bridge between specific transcriptional activators and the RNA polymerase II transcription machinery; therefore, our data suggest that MED16 may be a signaling component in the gap between the NPR1 signaling node and the general transcription machinery and may relay signals from both the SA and the JA/ET pathways.

Topics: Alternaria; Arabidopsis; Arabidopsis Proteins; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Mutation; Oxylipins; Plant Immunity; Pseudomonas syringae; Signal Transduction; Trans-Activators

Cauliflower mosaic virus (CaMV) encodes a multifunctional protein P6 that is required for translation of the 35S RNA and also acts as a suppressor of RNA silencing. Here we demonstrate that P6 additionally acts as a pathogenicity effector of an unique and novel type, modifying NPR1 (a key regulator of salicylic acid (SA)- and jasmonic acid (JA)-dependent signaling) and inhibiting SA-dependent defence responses We find that that transgene-mediated expression of P6 in Arabidopsis and transient expression in Nicotiana benthamiana has profound effects on defence signaling, suppressing expression of representative SA-responsive genes and increasing expression of representative JA-responsive genes. Relative to wild-type Arabidopsis P6-expressing transgenics had greatly reduced expression of PR-1 following SA-treatment, infection by CaMV or inoculation with an avirulent bacterial pathogen Pseudomonas syringae pv tomato (Pst). Similarly transient expression in Nicotiana benthamiana of P6 (including a mutant form defective in translational transactivation activity) suppressed PR-1a transcript accumulation in response to Agrobacterium infiltration and following SA-treatment. As well as suppressing the expression of representative SA-regulated genes, P6-transgenic Arabidopsis showed greatly enhanced susceptibility to both virulent and avirulent Pst (titres elevated 10 to 30-fold compared to non-transgenic controls) but reduced susceptibility to the necrotrophic fungus Botrytis cinerea. Necrosis following SA-treatment or inoculation with avirulent Pst was reduced and delayed in P6-transgenics. NPR1 an important regulator of SA/JA crosstalk, was more highly expressed in the presence of P6 and introduction of the P6 transgene into a transgenic line expressing an NPR1:GFP fusion resulted in greatly increased fluorescence in nuclei even in the absence of SA. Thus in the presence of P6 an inactive form of NPR1 is mislocalized in the nucleus even in uninduced plants. These results demonstrate that P6 is a new type of pathogenicity effector protein that enhances susceptibility to biotrophic pathogens by suppressing SA- but enhancing JA-signaling responses.

Topics: Analysis of Variance; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Immunity, Innate; Microscopy, Fluorescence; Nicotiana; Oxylipins; Plant Diseases; Plants, Genetically Modified; Salicylic Acid; Signal Transduction; Trans-Activators; Trypan Blue; Virulence Factors

The Arabidopsis Ca(2+)/calmodulin (CaM)-binding transcription factor SIGNAL RESPONSIVE1 (AtSR1/CAMTA3) was previously identified as a key negative regulator of plant immune responses. Here, we report a new role for AtSR1 as a critical component of plant defense against insect herbivory. Loss of AtSR1 function impairs tolerance to feeding by the generalist herbivore Trichoplusia ni as well as wound-induced jasmonate accumulation. The susceptibility of the atsr1 mutant is associated with decreased total glucosinolate (GS) levels. The two key herbivory deterrents, indol-3-ylmethyl (I3M) and 4-methylsulfinylbutyl (4MSOB), showed the most significant reductions in atsr1 plants. Further, changes in AtSR1 transcript levels led to altered expression of several genes involved in GS metabolism including IQD1, MYB51 and AtST5a. Overall, our results establish AtSR1 as an important component of plant resistance to insect herbivory as well as one of only three described proteins involved in Ca(2+)/CaM-dependent signaling to function in the regulation of GS metabolism, providing a novel avenue for future investigations of plant-insect interactions.

Topics: Animals; Arabidopsis; Arabidopsis Proteins; Calcium Signaling; Calmodulin; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glucosinolates; Herbivory; Moths; Mutation; Oxylipins; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Protein Serine-Threonine Kinases; RNA, Plant; Transcription Factors; Wounds and Injuries

The plant hormone jasmonic acid (JA) has a crucial role in both host immunity and development in plants. Here, we report the importance of JA signaling in the defense system of rice. Exogenous application of JA conferred resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo) in rice. Expression of OsJAZ8, a rice jasmonate ZIM-domain protein, was highly up-regulated by JA. OsJAZ8 interacted with a putative OsCOI1, which is a component of the SCF(COI1) E3 ubiquitin ligase complex, in a coronatine-dependent manner. OsJAZ8 also formed heterodimers with other OsJAZ proteins but did not form homodimer. JA treatment caused OsJAZ8 degradation and this degradation was dependent on the 26S proteasome pathway. Furthermore, the JA-dependent OsJAZ8 degradation was mediated by the Jas domain. Transgenic rice plants overexpressing OsJAZ8ΔC, which lacks the Jas domain, exhibited a JA-insensitive phenotype. A large-scale analysis using a rice DNA microarray revealed that overexpression of OsJAZ8ΔC altered the expression of JA-responsive genes, including defense-related genes, in rice. Furthermore, OsJAZ8ΔC negatively regulated the JA-induced resistance to Xoo in rice. On the basis of these data, we conclude that JA plays an important role in resistance to Xoo, and OsJAZ8 acts as a repressor of JA signaling in rice.

Topics: Cyclopentanes; Dimerization; Disease Resistance; Gene Expression; Gene Expression Profiling; Gene Expression Regulation, Plant; Oligonucleotide Array Sequence Analysis; Oryza; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Proteins; Plants, Genetically Modified; Proteasome Endopeptidase Complex; Protein Stability; Protein Structure, Tertiary; Proteolysis; Signal Transduction; Two-Hybrid System Techniques; Up-Regulation; Xanthomonas

Nitric oxide (NO) is known for its role in the activation of plant defense responses. To examine the involvement and mode of action of NO in plant defense responses, we introduced calmodulin-dependent mammalian neuronal nitric oxide synthase (nNOS), which controls the CaMV35S promoter, into wild-type and NahG tobacco plants. Constitutive expression of nNOS led to NO production and triggered spontaneous induction of leaf lesions. Transgenic plants accumulated high amounts of H(2)O(2), with catalase activity lower than that in the wild type. nNOS transgenic plants contained high levels of salicylic acid (SA), and they induced an array of SA-, jasmonic acid (JA)-, and/or ethylene (ET)-related genes. Consequently, NahG co-expression blocked the induction of systemic acquired resistance (SAR)-associated genes in transgenic plants, implying SA is involved in NO-mediated induction of SAR genes. The transgenic plants exhibited enhanced resistance to a spectrum of pathogens, including bacteria, fungi, and viruses. Our results suggest a highly ranked regulatory role for NO in SA-, JA-, and/or ET-dependent pathways that lead to disease resistance.

Topics: Animals; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Hydrogen Peroxide; Nicotiana; Nitric Oxide Synthase; Oxylipins; Plants, Genetically Modified; Pseudomonas; Rats; Salicylic Acid

In the present study, we evaluated the role of the defense-related gene OCP3 in callose deposition as a response to two necrotrophic fungal pathogens, Botrytis cinerea and Plectosphaerella cucumerina. ocp3 plants exhibited accelerated and intensified callose deposition in response to fungal infection associated with enhanced disease resistance to the two pathogens. A series of double mutant analyses showed potentiation of callose deposition and the heightened disease resistance phenotype in ocp3 plants required the plant hormone abscisic acid (ABA) and the PMR4 gene encoding a callose synthase. This finding was congruent with an observation that ocp3 plants exhibited increased ABA accumulation, and ABA was rapidly synthesized following fungal infection in wild-type plants. Furthermore, we determined that potentiation of callose deposition in ocp3 plants, including enhanced disease resistance, also required jasmonic acid (JA) recognition though a COI1 receptor, however JA was not required for basal callose deposition following fungal infection. In addition, potentiation of callose deposition in ocp3 plants appeared to follow a different mechanism than that proposed for callose β-amino-butyric acid (BABA)-induced resistance and priming, because ocp3 plants responded to BABA-induced priming for callose deposition and induced resistance of a magnitude similar to that observed in wild-type plants. Our results point to a model in which OCP3 represents a specific control point for callose deposition regulated by JA yet ultimately requiring ABA. These results provide new insights into the mechanism of callose deposition regulation in response to pathogen attack; however the complexities of the processes remain poorly understood.

Topics: Abscisic Acid; Adaptation, Physiological; Aminobutyrates; Arabidopsis; Arabidopsis Proteins; Ascomycota; Botrytis; Cyclopentanes; Disease Resistance; Droughts; Gene Expression Regulation, Plant; Glucans; Glucosyltransferases; Homeodomain Proteins; Mutation; Oxylipins; Phenotype; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Signal Transduction; Transcription Factors

The Rpv3 locus determines the ability to operate an isolate-specific hypersensitive response (HR) against Plasmopara viticola in grapevines that carry a resistant Rpv3 (+) haplotype. Artificial infection was performed on leaf discs of Rpv3 (+) and Rpv3 (-) grapevines with two distinct isolates of the pathogen (avrRpv3 (+) and avrRpv3 (-)). The plant response, including the establishment of HR and changes in expression of 33 genes, was compared to the development of the pathogen. HR was induced exclusively in the Rpv3 (+) host upon inoculation with the avrRpv3 (+) isolate of the pathogen, which is assumed to use avrRpv3 (+) effectors that are recognised by/through the plant Rpv3 (+) gene product. The limitation imposed on pathogen growth was the result of inducible responses elicited by the Rpv3 (+)-avrRpv3 (+) interaction. This host reaction relied on transcriptional induction of the HR-associated gene HSR1 and salicylic acid-induced pathogenesis-related (PR) genes PR-1 and PR-2 during the initial 24-48 h post-inoculation. These events had no parallel in the Rpv3 (-) host or upon infection with the avrRpv3 (-) isolate. The emerging model for Rpv3-mediated defence, which is dependent upon race-specific recognition, associated with up-regulation of PR-1 and PR-2 genes, and enforced by localised HR-type necrosis, is compatible with the cascade of events initiated by the products of NB-LRR and LRR-kinase receptor-like genes, such as those residing in the Rpv3 locus.

Topics: Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Haplotypes; Host-Pathogen Interactions; Oomycetes; Oxylipins; Phenotype; Plant Diseases; Plant Immunity; Plant Leaves; Plant Proteins; Salicylic Acid; Signal Transduction; Species Specificity; Time Factors; Up-Regulation; Virulence; Vitis

Protease inhibitors (PIs) function in the precise regulation of proteases, and are thus involved in diverse biological processes in many organisms. Here, we studied the functions of the Arabidopsis UNUSUAL SERINE PROTEASE INHIBITOR (UPI) gene, which encodes an 8.8 kDa protein of atypical sequence relative to other PIs. Plants harboring a loss-of-function UPI allele displayed enhanced susceptibility to the necrotrophic fungi Botrytis cinerea and Alternaria brassicicola as well as the generalist herbivore Trichoplusia ni. Further, ectopic expression conferred increased resistance to B. cinerea and T. ni. In contrast, the mutant has wild-type responses to virulent, avirulent and non-pathogenic strains of Pseudomonas syringae, thus limiting the defense function of UPI to necrotrophic fungal infection and insect herbivory. Expression of UPI is significantly induced by jasmonate, salicylic acid and abscisic acid, but is repressed by ethylene, indicating complex phytohormone regulation of UPI expression. The upi mutant also shows significantly delayed flowering, associated with decreased SOC1 expression and elevated levels of MAF1, two regulators of floral transition. Recombinant UPI strongly inhibits the serine protease chymotrypsin but also weakly blocks the cysteine protease papain. Interestingly, jasmonate induces intra- and extracellular UPI accumulation, suggesting a possible role in intercellular or extracellular functions. Overall, our results show that UPI is a dual-specificity PI that functions in plant growth and defense, probably through the regulation of endogenous proteases and/or those of biotic invaders.

Topics: Abscisic Acid; Alternaria; Amino Acid Sequence; Animals; Arabidopsis; Arabidopsis Proteins; Botrytis; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Herbivory; Insecta; Molecular Sequence Data; Oxylipins; Plant Diseases; Plant Growth Regulators; Plants, Genetically Modified; Protease Inhibitors; Pseudomonas syringae; Salicylic Acid

Botrytis cinerea is a major pre- and post-harvest necrotrophic pathogen with a broad host range that causes substantial crop losses. The plant hormone jasmonic acid (JA) is involved in the basal resistance against this fungus. Despite basal resistance, virulent strains of B. cinerea can cause disease on Arabidopsis thaliana and virulent pathogens can interfere with the metabolism of the host in a way to facilitate infection of the plant. However, plant genes that are required by the pathogen for infection remain poorly described. To find such genes, we have compared the changes in gene expression induced in A. thaliana by JA with those induced after B. cinerea using genome-wide microarrays. We have identified genes that are repressed by JA but that are induced by B. cinerea. In this study, we describe one candidate gene, ATGRXS13, that encodes for a putative glutaredoxin and that exhibits such a crossed expression. In plants that are infected by this necrotrophic fungus, ATGRXS13 expression was negatively controlled by JA and TGA transcription factors but also through a JA-salicylic acid (SA) cross-talk mechanism as B. cinerea induced SA production that positively controlled ATGRXS13 expression. Furthermore, plants impaired in ATGRXS13 exhibited resistance to B. cinerea. Finally, we present a model whereby B. cinerea takes advantage of defence signalling pathways of the plant to help the colonization of its host.

Topics: Alternative Splicing; Amino Acid Sequence; Arabidopsis; Arabidopsis Proteins; Botrytis; Cloning, Molecular; Cyclopentanes; Disease Resistance; Gene Expression Regulation, Plant; Glutaredoxins; Molecular Sequence Data; Mutagenesis, Insertional; Oligonucleotide Array Sequence Analysis; Oxylipins; Plant Diseases; RNA, Plant; Salicylic Acid; Signal Transduction; Transcription Factors

Cytokinins are phytohormones that are involved in various regulatory processes throughout plant development, but they are also produced by pathogens and known to modulate plant immunity. A novel transgenic approach enabling autoregulated cytokinin synthesis in response to pathogen infection showed that cytokinins mediate enhanced resistance against the virulent hemibiotrophic pathogen Pseudomonas syringae pv tabaci. This was confirmed by two additional independent transgenic approaches to increase endogenous cytokinin production and by exogenous supply of adenine- and phenylurea-derived cytokinins. The cytokinin-mediated resistance strongly correlated with an increased level of bactericidal activities and up-regulated synthesis of the two major antimicrobial phytoalexins in tobacco (Nicotiana tabacum), scopoletin and capsidiol. The key role of these phytoalexins in the underlying mechanism was functionally proven by the finding that scopoletin and capsidiol substitute in planta for the cytokinin signal: phytoalexin pretreatment increased resistance against P. syringae. In contrast to a cytokinin defense mechanism in Arabidopsis (Arabidopsis thaliana) based on salicylic acid-dependent transcriptional control, the cytokinin-mediated resistance in tobacco is essentially independent from salicylic acid and differs in pathogen specificity. It is also independent of jasmonate levels, reactive oxygen species, and high sugar resistance. The novel function of cytokinins in the primary defense response of solanaceous plant species is rather mediated through a high phytoalexin-pathogen ratio in the early phase of infection, which efficiently restricts pathogen growth. The implications of this mechanism for the coevolution of host plants and cytokinin-producing pathogens and the practical application in agriculture are discussed.

Topics: Anti-Infective Agents; beta-Fructofuranosidase; Cyclopentanes; Cytokinins; Disease Resistance; Host-Pathogen Interactions; Nicotiana; Oxylipins; Phytoalexins; Plant Diseases; Plant Immunity; Plant Leaves; Plants, Genetically Modified; Pseudomonas syringae; Salicylic Acid; Scopoletin; Sesquiterpenes

Two wheat varieties HD-29 (resistant, R) and WH-542 (susceptible, S) were pretreated with jasmonic acid (JA) or jasmonate and then artificially inoculated with sporidial suspension of Tilletia indica to study its influence in reducing Karnal bunt (KB) infection by regulating cystatin gene expression. JA was found to improve the plant defense against KB as its exogenous application resulted in decrease in coefficient of infection (CI) in both susceptible and resistant varieties following pathogen inoculation. Transcript profiling of wheat cystatin genes at different days after inoculation (DAI) showed that JA pretreatment positively induced cystatin gene expression in both varieties with greater induction of expression in resistant variety than the susceptible one (P< 0.05). Different temporal expression of three wheat cystatin genes, WC2, WC3 and WCMD was observed with their increased expression at 1DAI in the boot emergence stage which is most susceptible to KB and then slowly declined gradually at 3, 7 and 15 DAI in both the varieties. Except WC2, higher expression of other two cystatins viz. WC3 and WCMD at 1DAI showed higher response (P< 0.05) to KB pathogenesis at the disease-prone boot emergence stage as also evident by decrease of CI in both varieties. The results of determination of specific activity of cystatin by inhibitor assay were found to be consistent with those of transcript profiling. These findings suggest that jasmonic acid (JA) may act as a potential activator of induced resistance against Karnal bunt of wheat by upregulating cystatin gene expression.

Topics: Biological Assay; Cloning, Molecular; Crops, Agricultural; Cyclopentanes; Cystatins; Cysteine Proteinase Inhibitors; Disease Resistance; Gene Expression Profiling; Gene Expression Regulation, Plant; Genes, Plant; Multigene Family; Oxylipins; Phylogeny; Plant Diseases; Reverse Transcriptase Polymerase Chain Reaction; Signal Transduction; Spores, Fungal; Transcription, Genetic; Triticum; Ustilaginales

Systemic acquired resistance (SAR) is a defense mechanism induced in the distal parts of plants after primary infection. It confers long-lasting protection against a broad spectrum of microbial pathogens. Lack of high-throughput assays has hampered the forward genetic analysis of SAR. Here, we report the development of an easy and efficient assay for SAR and its application in a forward genetic screen for SAR-deficient mutants in Arabidopsis (Arabidopsis thaliana). Using the new assay for SAR, we identified six flavin-dependent monooxygenase1, four AGD2-like defense response protein1, three salicylic acid induction-deficient2, one phytoalexin deficient4, and one avrPphB-susceptible3 alleles as well as a gain-of-function mutant of CALMODULIN-BINDING TRANSCRIPTION ACTIVATOR3 designated camta3-3D. Like transgenic plants overexpressing CAMTA3, camta3-3D mutant plants exhibit compromised SAR and enhanced susceptibility to virulent pathogens, suggesting that CAMTA3 is a critical regulator of both basal resistance and SAR.

Topics: Alleles; Arabidopsis; Arabidopsis Proteins; Cloning, Molecular; Cyclopentanes; Disease Resistance; Ethylenes; Genetic Testing; High-Throughput Screening Assays; Mutation; Oxylipins; Peronospora; Plant Diseases; Plant Leaves; Pseudomonas syringae; Salicylic Acid

Filamentous fungi belonging to the genus Trichoderma have long been recognized as agents for the biocontrol of plant diseases. In this work, we investigated the mechanisms involved in the defense responses of Arabidopsis thaliana seedlings elicited by co-culture with Trichoderma virens and Trichoderma atroviride. Interaction of plant roots with fungal mycelium induced growth and defense responses, indicating that both processes are not inherently antagonist. Expression studies of the pathogenesis-related reporter markers pPr1a:uidA and pLox2:uidA in response to T. virens or T. atroviride provided evidence that the defense signaling pathway activated by these fungi involves salicylic acid (SA) and/or jasmonic acid (JA) depending on the amount of conidia inoculated. Moreover, we found that Arabidopsis seedlings colonized by Trichoderma accumulated hydrogen peroxide and camalexin in leaves. When grown under axenic conditions, T. virens produced indole-3-carboxaldehyde (ICAld) a tryptophan-derived compound with activity in plant development. In Arabidopsis seedlings whose roots are in contact with T. virens or T. atroviride, and challenged with Botrytis cinerea in leaves, disease severity was significantly reduced compared to axenically grown seedlings. Our results indicate that the defense responses elicited by Trichoderma in Arabidopsis are complex and involve the canonical defense hormones SA and JA as well as camalexin, which may be important factors in boosting plant immunity.

Topics: Arabidopsis; Biomass; Botrytis; Cyclopentanes; Disease Resistance; Gas Chromatography-Mass Spectrometry; Gene Expression Regulation, Plant; Hydrogen Peroxide; Indoles; Oxylipins; Plant Diseases; Plant Growth Regulators; Plant Immunity; Plant Leaves; Plant Roots; Salicylic Acid; Seedlings; Thiazoles; Trichoderma

The oxylipin pathway is of central importance for plant defensive responses. Yet, the first step of the pathway, the liberation of linolenic acid following induction, is poorly understood. Phospholipases D (PLDs) have been hypothesized to mediate this process, but data from Arabidopsis (Arabidopsis thaliana) regarding the role of PLDs in plant resistance have remained controversial. Here, we cloned two chloroplast-localized PLD genes from rice (Oryza sativa), OsPLDα4 and OsPLDα5, both of which were up-regulated in response to feeding by the rice striped stem borer (SSB) Chilo suppressalis, mechanical wounding, and treatment with jasmonic acid (JA). Antisense expression of OsPLDα4 and -α5 (as-pld), which resulted in a 50% reduction of the expression of the two genes, reduced elicited levels of linolenic acid, JA, green leaf volatiles, and ethylene and attenuated the SSB-induced expression of a mitogen-activated protein kinase (OsMPK3), a lipoxygenase (OsHI-LOX), a hydroperoxide lyase (OsHPL3), as well as a 1-aminocyclopropane-1-carboxylic acid synthase (OsACS2). The impaired oxylipin and ethylene signaling in as-pld plants decreased the levels of herbivore-induced trypsin protease inhibitors and volatiles, improved the performance of SSB and the rice brown planthopper Nilaparvata lugens, and reduced the attractiveness of plants to a larval parasitoid of SSB, Apanteles chilonis. The production of trypsin protease inhibitors in as-pld plants could be partially restored by JA, while the resistance to rice brown planthopper and SSB was restored by green leaf volatile application. Our results show that phospholipases function as important components of herbivore-induced direct and indirect defenses in rice.

Topics: alpha-Linolenic Acid; Animals; Chloroplast Proteins; Chloroplasts; Cyclopentanes; Disease Resistance; Ethylenes; Gene Expression Regulation, Plant; Hemiptera; Herbivory; Lepidoptera; Oils, Volatile; Oryza; Oxylipins; Phospholipase D; Plant Diseases; Plant Oils; Plant Proteins; Plants, Genetically Modified; RNA, Antisense; Signal Transduction

Norway spruce [Picea abies (L.) Karst.] is one of the economically most important conifer species in Europe. The major pathogen on Norway spruce is Heterobasidion parviporum (Fr.) Niemelä & Korhonen. To achieve a better understanding of Norway spruce's defence mechanisms, transcriptional responses in bark to H. parviporum infection were compared with the response to wounding using cDNA-amplified fragment length polymorphism. The majority of the recovered transcript-derived fragments (TDFs) showed a similar expression pattern for infection and wounding treatment, although inoculated samples showed an enhanced reaction. Genes related to systemic acquired resistance, e.g., PR1, accumulated after H. parviporum infection. Simultaneously, several transcripts involved in various aspects of jasmonic acid (JA)- and ethylene (ET)-mediated signalling accumulated. Genes involved in the ubiquitin/proteasome system were also regulated. Expression patterns have been confirmed by quantitative polymerase chain reaction. The expression patterns of the isolated TDFs suggest that infection with H. parviporum in Norway spruce induces a broad defence, with many similarities to non-specific defence responses in angiosperms. The parallel induction of salicylic acid- and JA/ET-mediated pathways implies spatially separated responses in different cell layers, with and without hyphal contact. A set of TDFs were analysed in an independent experiment with unrelated material treated with wounding or with inoculation with H. parviporum or Phlebiopsis gigantea, verifying the original observations and underlining the non-specific defence responses. In addition, our data suggest that rerouting of carbon in secondary metabolism is an integral part of Norway spruce induced defence. We report the sequences of three 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase genes (PaDAHP1, PaDAHP2 and PaDAHP3) and their relative expression in response to wounding and infection with H. parviporum and P. gigantea. The results clearly indicate differential regulation of the three DAHPs in the induced defence responses in Norway spruce. This study gives insights into the central mechanisms in the induced defences in Norway spruce.

Topics: Amplified Fragment Length Polymorphism Analysis; Base Sequence; Basidiomycota; Carbon; Cyclopentanes; Disease Resistance; DNA, Complementary; Ethylenes; Gene Expression Regulation, Plant; Genes, Plant; Magnoliopsida; Oxylipins; Picea; Plant Bark; Plant Diseases; Proteasome Endopeptidase Complex; Salicylic Acid; Signal Transduction; Sugar Acids; Transcription, Genetic; Ubiquitin

A germin-like gene (CchGLP) cloned from geminivirus-resistant pepper (Capsicum chinense Jacq. Line BG-3821) was characterized and the enzymatic activity of the expressed protein analyzed. The predicted protein consists of 203 amino acids, similar to other germin-like proteins. A highly conserved cupin domain and typical germin boxes, one of them containing three histidines and one glutamate, are also present in CchGLP. A signal peptide was predicted in the first 18 N-terminal amino acids, as well as one putative N-glycosylation site from residues 44-47. CchGLP was expressed in E. coli and the recombinant protein displayed manganese superoxide dismutase (Mn-SOD) activity. Molecular analysis showed that CchGLP is present in one copy in the C. chinense Jacq. genome and was induced in plants by ethylene (Et) and salicylic acid (SA) but not jasmonic acid (JA) applications in the absence of pathogens. Meanwhile, incompatible interactions with either Pepper golden mosaic virus (PepGMV) or Pepper huasteco yellow vein virus (PHYVV) caused local and systemic CchGLP induction in these geminivirus-resistant plants, but not in a susceptible accession. Compatible interactions with PHYVV, PepGMV and oomycete Phytophthora capsici did not induce CchGLP expression. Thus, these results indicate that CchGLP encodes a Mn-SOD, which is induced in the C. chinense geminivirus-resistant line BG-3821, likely using SA and Et signaling pathways during incompatible interactions with geminiviruses PepGMV and PHYVV.

Topics: Capsicum; Cloning, Molecular; Computational Biology; Cyclopentanes; Disease Resistance; Escherichia coli; Ethylenes; Geminiviridae; Gene Expression Regulation, Plant; Glycoproteins; Mosaic Viruses; Oxylipins; Phytophthora; Plant Diseases; Plant Proteins; Recombinant Proteins; Salicylic Acid; Sequence Analysis, DNA; Superoxide Dismutase

Heterotrimeric G proteins are involved in the defense response against necrotrophic fungi in Arabidopsis. In order to elucidate the resistance mechanisms involving heterotrimeric G proteins, we analyzed the effects of the Gβ (subunit deficiency in the mutant agb1-2 on pathogenesis-related gene expression, as well as the genetic interaction between agb1-2 and a number of mutants of established defense pathways. Gβ-mediated signaling suppresses the induction of salicylic acid (SA)-, jasmonic acid (JA)-, ethylene (ET)- and abscisic acid (ABA)-dependent genes during the initial phase of the infection with Fusarium oxysporum (up to 48 h after inoculation). However, at a later phase it enhances JA/ET-dependent genes such as PDF1.2 and PR4. Quantification of the Fusarium wilt symptoms revealed that Gβ- and SA-deficient mutants were more susceptible than wild-type plants, whereas JA- and ET-insensitive and ABA-deficient mutants demonstrated various levels of resistance. Analysis of the double mutants showed that the Gβ-mediated resistance to F. oxysporum and Alternaria brassicicola was mostly independent of all of the previously mentioned pathways. However, the progressive decay of agb1-2 mutants was compensated by coi1-21 and jin1-9 mutations, suggesting that at this stage of F. oxysporum infection Gβ acts upstream of COI1 and ATMYC2 in JA signaling.

Topics: Abscisic Acid; Alternaria; Arabidopsis; Arabidopsis Proteins; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Cyclopentanes; Defensins; Disease Resistance; Ethylenes; Fusarium; Genes, Plant; GTP-Binding Protein beta Subunits; Heterotrimeric GTP-Binding Proteins; Host-Pathogen Interactions; Mutation; Oxylipins; Plant Diseases; Plant Leaves; Salicylic Acid; Signal Transduction; Time Factors