cellulase and jasmonic-acid

Xanthomonas oryzae pv. oryzae, the causal agent of bacterial blight of rice, secretes several cell wall degrading enzymes including cellulase (ClsA) and lipase/esterase (LipA). Prior treatment of rice leaves with purified cell wall degrading enzymes such as LipA can confer enhanced resistance against subsequent X. oryzae pv. oryzae infection. To understand LipA-induced rice defense responses, microarray analysis was performed 12 h after enzyme treatment of rice leaves. This reveals that 867 (720 upregulated and 147 downregulated) genes are differentially regulated (≥2-fold). A number of genes involved in defense, stress, signal transduction, and catabolic processes were upregulated while a number of genes involved in photosynthesis and anabolic processes were downregulated. The microarray data also suggested upregulation of jasmonic acid (JA) biosynthetic and JA-responsive genes. Estimation of various phytohormones in LipA-treated rice leaves demonstrated a significant increase in the level of JA-Ile (a known active form of JA) while the levels of other phytohormones were not changed significantly with respect to buffer-treated control. This suggests a role for JA-Ile in cell wall damage induced innate immunity. Furthermore, a comparative analysis of ClsA- and LipA-induced rice genes has identified key rice functions that might be involved in elaboration of damage-associated molecular pattern (DAMP)-induced innate immunity.

Topics: Bacterial Proteins; Cellulase; Cyclopentanes; Esterases; Gene Expression Regulation, Plant; Immunity, Innate; Lipase; Oryza; Oxylipins; Plant Leaves; Salicylic Acid; Transcriptome; Up-Regulation

During plant-pathogen interactions, the plant cell wall forms part of active defence against invaders. In recent years, cell wall-editing enzymes, associated with growth and development, have been related to plant susceptibility or resistance. Our previous work identified a role for several tomato and Arabidopsis endo-1,4-β-glucanases (EGs) in plant-pathogen interactions. Here we studied the response of the Arabidopsis thaliana T-DNA insertion mutant lacking EG Korrigan1 (KOR1) infected with Pseudomonas syringae. KOR1 is predicted to be an EG which is thought to participate in cellulose biosynthesis. We found that kor1-1 plants were more susceptible to P. syringae, and displayed severe disease symptoms and enhanced bacterial growth if compared to Wassilewskija (Ws) wild-type plants. Hormonal and gene expression analyses revealed that the jasmonic acid (JA) pathway was activated more in kor1-1 plants with an increase in the JA-biosynthesis gene LOX3 and a greater accumulation of JA. Upon infection the accumulation of JA and JA-isoleucine (JA-Ile) was higher than in wild-type plants and increased the induction of LOX3 and the JA-responsive PDF1.2 gene. In addition, the increase of salicylic acid (SA) in healthy and infected kor1-1 may reflect the complex interaction between JA and SA, which results in the more susceptible phenotype displayed by the infected mutant plants. Callose deposition was enhanced in infected kor1-1 and an increase in pathogen-induced hydrogen peroxide took place. The susceptible phenotype displayed by KOR1-deficient plants was coronatine-independent. No significant changes were detected in the hormonal profile of the kor1-1 plants infected by coronatine-deficient P. syringae cmaA, which supports that absence of EG KOR1 alters per se the plant response to infection. We previously reported increased resistance of kor1-1 to B. cinerea, hence, the lack of this EG alters cell wall properties and plant responses in such a way that benefits P. syringae colonisation but restricts B. cinerea invasion.

Topics: Arabidopsis; Arabidopsis Proteins; Cell Wall; Cellulase; Cyclopentanes; DNA, Bacterial; Gene Expression Regulation, Plant; Lipoxygenase; Membrane Proteins; Oxylipins; Plant Diseases; Pseudomonas syringae; Salicylic Acid

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

The characterization of a non-photosynthetic isoform of NADP-malic enzyme (NADP-ME) from maize roots, which represents nearly 7% of the total soluble protein of this tissue, was performed. The molecular properties of the purified protein, as well as the kinetic parameters determined, indicate that the NADP-ME isoform present in maize roots differs from the photosynthetic enzyme implicated in the C4 cycle, but is similar, or identical, to the enzyme previously characterized from etiolated maize leaves (Maurino, Drincovich and Andreo, Biochem. Mol. Biol. Int. 38 (1996) 239-250). A full-length ORF encoding a plastidic NADP-ME (almost identical to the maize root NADP-ME, GenBank accession number U39958) was cloned from a root cDNA library as well as isolated by reverse transcription (RT)-PCR using green leaves mRNA as template. These results indicate that root NADP-ME does not constitute a root-specific isoform, but represents a protein with a constitutive pattern of expression in plastids of the C4 plant maize. The amount of NADP-ME measured by activity, western and northern blot was modified when different stress conditions (including treatments with cellulase, fungal elicitors, jasmonate and hypoxic treatment) were applied to maize roots, indicating that the enzyme from maize roots is under transcriptional or post-transcriptional regulation by effectors related to plant defence responses. It is deduced that the induction of housekeeping genes, like non-photosynthetic NADP-ME, whose constitutive role may be the provision of reductive power in non-photosynthetic plastids, is likely to accompany the defence response.

Topics: Cellulase; Cyclopentanes; DNA, Complementary; Electrophoresis, Polyacrylamide Gel; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Kinetics; Malate Dehydrogenase; Oxylipins; Plant Roots; Sequence Analysis, DNA; Zea mays

Plants are able to respond to herbivore damage with de novo biosynthesis of an herbivore-characteristic blend of volatiles. The signal transduction initiating volatile biosynthesis may involve the activation of the octadecanoid pathway, as exemplified by the transient increase of endogenous jasmonic acid (JA) in leaves of lima bean (Phaseolus lunatus) after treatment with the macromolecular elicitor cellulysin. Within this pathway lima bean possesses at least two different biologically active signals that trigger different biosynthetic activities. Early intermediates of the pathway, especially 12-oxo-phytodienoic acid (PDA), are able to induce the biosynthesis of the diterpenoid-derived 4,8, 12-trimethyltrideca-1,3,7,11-tetraene. High concentrations of PDA result in more complex patterns of additional volatiles. JA, the last compound in the sequence, lacks the ability to induce diterpenoid-derived compounds, but is highly effective at triggering the biosynthesis of other volatiles. The phytotoxin coronatine and amino acid conjugates of linolenic acid (e.g. linolenoyl-L-glutamine) mimic the action of PDA, but coronatine does not increase the level of endogenous JA. The structural analog of coronatine, the isoleucine conjugate of 1-oxo-indanoyl-4-carboxylic acid, effectively mimics the action of JA, but does not increase the level of endogenous JA. The differential induction of volatiles resembles previous findings on signal transduction in mechanically stimulated tendrils of Bryonia dioica.

Topics: alpha-Linolenic Acid; Amino Acids; Cellulase; Cucurbitaceae; Cyclopentanes; Fabaceae; Fatty Acids, Unsaturated; Indenes; Mevalonic Acid; Oils, Volatile; Oxylipins; Physical Stimulation; Plant Growth Regulators; Plant Leaves; Plants, Medicinal; Signal Transduction; Stearic Acids; Terpenes; Time Factors; Volatilization

Cellulysin, a crude cellulase from the plant parasitic fungus Trichoderma viride, induces the biosynthesis of volatiles in higher plants (Nicotiana plumbaginifolia, Phaseolus lunatus, and Zea mays) when applied to cut petioles by the transpiration stream. The pattern of the emitted volatiles largely resembles that from a herbivore damage or treatment of the plants with jasmonic acid (JA) indicating that cellulysin acts via activation of the octadecanoid signalling pathway. The treatment with cellulysin raises the level of endogenous JA after 30 min and is followed by a transient emission of ethylene after 2-3 h. Volatile production becomes significant after 12-24 h. Inhibitors of the JA pathway effectively block the cellulysin-dependent volatile biosynthesis.

Topics: Cellulase; Chromatography, Gas; Cyclopentanes; Ethylenes; Fabaceae; Kinetics; Nicotiana; Oxylipins; Plants; Plants, Medicinal; Plants, Toxic; Signal Transduction; Stearic Acids; Trichoderma; Zea mays