Abstract
Green leaf volatiles (GLVs) are C6-molecules – alcohols, aldehydes, and esters – produced by plants upon herbivory or during pathogen infection. Exposure to this blend of volatiles induces defense-related responses in neighboring undamaged plants, thus assigning a role to GLVs in regulating plant defenses. Here we compared Arabidopsis thaliana ecotype Landsberg erecta (Ler) with a hydroperoxide lyase line, hpl1, unable to synthesize GLVs, for susceptibility to Pseudomonas syringae pv. tomato (DC3000). We found that the growth of DC3000 was significantly reduced in the hpl1 mutant. This phenomenon correlated with lower jasmonic acid (JA) levels and higher salicylic acid levels in the hpl1 mutant. Furthermore, upon infection, the JA-responsive genes VSP2 and LEC were only slightly or not induced, respectively, in hpl1. This suggests that the reduced growth of DC3000 in hpl1 plants is due to the constraint of JA-dependent responses. Treatment of hpl1 plants with E-2-hexenal, one of the more reactive GLVs, prior to infection with DC3000, resulted in increased growth of DC3000 in hpl1, thus complementing this mutant. Interestingly, the growth of DC3000 also increased in Ler plants treated with E-2-hexenal. This stronger growth was not dependent on the JA-signaling component MYC2, but on ORA59, an integrator of JA and ethylene signaling pathways, and on the production of coronatine by DC3000. GLVs may have multiple effects on plant–pathogen interactions, in this case reducing resistance to Pseudomonas syringae via JA and ORA59.
Highlights
Plants produce green leaf volatiles (GLVs), C6-aldehydes, C6alcohols, and their acetates, through the lipoxygenase (LOX) and hydroperoxide lyase (HPL) pathways
Examples of this are found in Zea mays, Citrus jambhiri, Nicotiana attenuata, Gossypium hirsutum, Lycopersicon esculentum, and Arabidopsis thaliana plants where GLV perception induces the transcription of genes known to be involved in defense responses, or in biosynthesis of defense-related secondary metabolites (Bate and Rothstein, 1998; Arimura et al, 2001; Gomi et al, 2003; Weber et al, 2004; Farag et al, 2005; Kishimoto et al, 2005, 2006; Paschold et al, 2006), resulting in the production of defensive compounds (Zeringue, 1992; Bate and Rothstein, 1998; Farag and Paré, 2002; Engelberth et al, 2004; Farag et al, 2005; Ruther and Fürstenau, 2005; Kishimoto et al, 2006; Yan and Wang, 2006)
E -2-HEXENAL TREATMENT INCREASES SUSCEPTIBILITY TO DC3000 Since hpl1 is unable to produce GLVs, we addressed the question whether application of GLVs would restore its susceptibility to DC3000 comparable to Landsberg erecta (Ler)
Summary
Plants produce green leaf volatiles (GLVs), C6-aldehydes, C6alcohols, and their acetates, through the lipoxygenase (LOX) and hydroperoxide lyase (HPL) pathways. Pre-treatment with the C6-aldehyde E-2-hexenal as well as genetic manipulation to enhance C6-volatile production, resulted in increased resistance against the necrotrophic fungus Botrytis cinerea in Arabidopsis, most likely as a result of both activation of defense responses and direct inhibition of fungal growth (Kishimoto et al, 2005; Shiojiri et al, 2006b) Since all this evidence indicates a role for GLVs in regulating plant responses to bacterial pathogens and GLV levels have been shown to increase in plants upon infection with Pseudomonas syringae (Croft et al, 1993; Heiden et al, 2003), we decided to further dissect the role of GLVs in the interaction of plants with this pathogen. We found evidence that this is mediated by the transcription factor ORA59, one of the main players in the JA-signaling pathways, and required the production of the bacterial toxin COR
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
