jasmonic-acid and diphenyleneiodonium

Jasmonic acid (JA) is a well-characterized signaling molecule in plant defense responses. However, its relationships with other signal molecules in secondary metabolite production induced by endophytic fungus are largely unknown. Atractylodes lancea (Asteraceae) is a traditional Chinese medicinal plant that produces antimicrobial volatiles oils. We incubated plantlets of A. lancea with the fungus Gilmaniella sp. AL12. to research how JA interacted with other signal molecules in volatile oil production.. Fungal inoculation increased JA generation and volatile oil accumulation. To investigate whether JA is required for volatile oil production, plantlets were treated with JA inhibitors ibuprofen (IBU) and nordihydroguaiaretic acid. The inhibitors suppressed both JA and volatile oil production, but fungal inoculation could still induce volatile oils. Plantlets were further treated with the nitric oxide (NO)-specific scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt (cPTIO), the H2O2 inhibitors diphenylene iodonium (DPI) and catalase (CAT), and the salicylic acid (SA) biosynthesis inhibitors paclobutrazol and 2-aminoindan-2-phosphonic acid. With fungal inoculation, IBU did not inhibit NO production, and JA generation was significantly suppressed by cPTIO, showing that JA may act as a downstream signal of the NO pathway. Exogenous H2O2 could reverse the inhibitory effects of cPTIO on JA generation, indicating that NO mediates JA induction by the fungus through H2O2-dependent pathways. With fungal inoculation, the H2O2 scavenger DPI/CAT could inhibit JA generation, but IBU could not inhibit H2O2 production, implying that H2O2 directly mediated JA generation. Finally, JA generation was enhanced when SA production was suppressed, and vice versa.. Jasmonic acid acts as a downstream signaling molecule in NO- and H2O2-mediated volatile oil accumulation induced by endophytic fungus and has a complementary interaction with the SA signaling pathway.

Topics: Antioxidants; Atractylodes; Benzoates; Catalase; Cyclopentanes; Endophytes; Enzyme Inhibitors; Free Radical Scavengers; Fungi; Hydrogen Peroxide; Imidazoles; Indans; Masoprocol; Nitric Oxide; Oils, Volatile; Onium Compounds; Organophosphonates; Oxylipins; Plant Diseases; Plants, Medicinal; Salicylic Acid; Signal Transduction; Time Factors; Triazoles

The plant cell wall is a dynamic and complex structure whose functional integrity is constantly being monitored and maintained during development and interactions with the environment. In response to cell wall damage (CWD), putatively compensatory responses, such as lignin production, are initiated. In this context, lignin deposition could reinforce the cell wall to maintain functional integrity. Lignin is important for the plant's response to environmental stress, for reinforcement during secondary cell wall formation, and for long-distance water transport. Here, we identify two stages and several components of a genetic network that regulate CWD-induced lignin production in Arabidopsis (Arabidopsis thaliana). During the early stage, calcium and diphenyleneiodonium-sensitive reactive oxygen species (ROS) production are required to induce a secondary ROS burst and jasmonic acid (JA) accumulation. During the second stage, ROS derived from the NADPH oxidase RESPIRATORY BURST OXIDASE HOMOLOG D and JA-isoleucine generated by JASMONIC ACID RESISTANT1, form a negative feedback loop that can repress each other's production. This feedback loop in turn seems to influence lignin accumulation. Our results characterize a genetic network enabling plants to regulate lignin biosynthesis in response to CWD through dynamic interactions between JA and ROS.

Topics: Acetates; Arabidopsis; Arabidopsis Proteins; Calcium; Cell Wall; Cyclopentanes; Gene Expression Regulation, Plant; Genes, Plant; Lignin; Models, Biological; Mutation; Onium Compounds; Oxylipins; Phenotype; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; Seedlings; Signal Transduction

The phenylpropanoid pathway plays important roles in plants following exposure to environmental stresses, such as wounding and pathogen attack, which lead to the production of a variety of compounds, including lignin, flavonoids and phytoalexins. Ferulate 5-hydroxylase (F5H) is a cytochrome P450-dependent monooxygenase that catalyses the hydroxylation of ferulic acid, coniferaldehyde and coniferyl alcohol, leading to sinapic acid and syringyl lignin biosynthesis. We isolated F5H cDNA and genomic DNA from Camptotheca acuminata and investigated the expression pattern of the C. acuminata F5H (CaF5H1) gene in response to wounding. A search against the BLOCKS database of conserved protein motifs indicated that CaF5H1 retains features in common with F5Hs reported from other plants. 5'-flanking region analysis using the PLACE database showed that putative regulatory elements related to various abiotic and biotic stresses, such as drought, wounding, low temperature and pathogens, exist in the 5'-flanking region of CaF5H1. Based upon these analysis results, we investigated the expression pattern of CaF5H1 gene in response to wounding and stress-related molecules. Here, we show that CaF5H1 transcripts accumulated in the leaves in response to mechanical wounding or the application of molecules involved in the stress response, such as ethylene, ABA and hydrogen peroxide (H2O2). The application of salicylic acid and diphenylene iodonium (DPI) inhibited the wound-induced expression of CaF5H1. Taken together, we suggest that wound-induced expression of CaF5H1 may be mediated by MJ and H2O2 and enhanced phenylpropanoid contents via CaF5H1 maybe function in response to various stresses, including wounding, in plants.

Topics: Abscisic Acid; Acrolein; Amino Acid Sequence; Base Sequence; Camptotheca; Coumaric Acids; Cyclopentanes; Cytochrome P-450 Enzyme System; Ethylenes; Hydrogen Peroxide; Mixed Function Oxygenases; Molecular Sequence Data; Onium Compounds; Oxylipins; Phenols; Plant Leaves; Plant Roots; Plant Stems; Salicylic Acid; Sequence Alignment; Transcription, Genetic

Pea seedlings (Pisum sativum L.) were used as materials to test the timings and compartments of hydrogen peroxide (H2O2) triggered by wounding and exogenous jasmonic acid (JA). The results showed that H2O2 could be systemically induced by wounding and exogenous JA. H2O2 increased within 1 h and reached the peak 3-5 h after wounding in either the wounded leaves or the unwounded leaves adjacent to the wounded ones and the inferior leaves far from the wounded ones. After this, H2O2 decreased and recovered to the control level 12 h after wounding. The activities of antioxidant enzymes, however, were rapidly increased by wounding. Diphenylene iodonium (DPI), an inhibitor of NADPH oxidase, could significantly inhibit H2O2 burst that was mediated by wounding and exogenous JA. Assay of H2O2 subcellular location showed that H2O2 in response to wounding and exogenous JA was predominantly accumulated in plasma membrane, cell wall and apoplasmic space. Numerous JA (gold particles) was found via immunogold electron microscopy to be located in cell wall and phloem zones of mesophyll cell after wounding.

Topics: Chloroplasts; Cyclopentanes; Enzyme Inhibitors; Hydrogen Peroxide; Microscopy, Immunoelectron; NADPH Oxidases; Onium Compounds; Oxylipins; Pisum sativum; Plant Growth Regulators; Plant Leaves; Reactive Oxygen Species; Seedlings; Stress, Mechanical

Chitinase is a pathogenesis-related protein that hydrolyzes chitin, a major component of fungal cell walls. Two-week-old rice seedling leaf, leaf sheath and root tissues responded to an exogenous treatment by jasmonic acid (JA) with induction of the chitinases as determined by immunoblot analysis using an anti-endochitinase antibody. Induced accumulation of these chitinases was observed within 24 to 48 h in the leaf sheaths, leaves and roots. Besides, ethylene generator ethephon and abiotic stressor copper could also induce chitinases accumulation among various plant hormones and stress agents examined. Cycloheximide effectively blocked their accumulation by JA, suggesting that de novo protein synthesis is required. Partial blockage of the induced accumulation of chitinases by NADPH oxidase inhibitor and free radical scavengers suggested involvement of reactive oxygen species. Moreover, induced accumulation of these chitinases also by methyl jasmonate and certain protein phosphatase inhibitors indicated their potential importance and wider role in rice seedlings.

Topics: Acetates; Chitinases; Cycloheximide; Cyclopentanes; Enzyme Inhibitors; Ethylenes; Onium Compounds; Organophosphorus Compounds; Oryza; Oxylipins; Phosphoprotein Phosphatases; Plant Growth Regulators; Plant Structures; Reactive Oxygen Species