de Torres Zabala, Marta, Bennett, Mark H., Truman, William H. and Grant, Murray (2009) Antagonism between salicylic and abscisic acid reflects early host-pathogen conflict and moulds plant defence responses. The Plant Journal, 59 (3). pp. 375-386. doi:10.1111/j.1365-313X.2009.03875.x ISSN 0960-7412.

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Abstract

The importance of phytohormone balance is increasingly recognized as central to the outcome of plant–pathogen interactions. Recently it has been demonstrated that abscisic acid signalling pathways are utilized by the bacterial phytopathogen Pseudomonas syringae to promote pathogenesis. In this study, we examined the dynamics, inter-relationship and impact of three key acidic phytohormones, salicylic acid, abscisic acid and jasmonic acid, and the bacterial virulence factor, coronatine, during progression of P. syringae infection of Arabidopsis thaliana. We show that levels of SA and ABA, but not JA, appear to play important early roles in determining the outcome of the infection process. SA is required in order to mount a full innate immune responses, while bacterial effectors act rapidly to activate ABA biosynthesis. ABA suppresses inducible innate immune responses by down-regulating SA biosynthesis and SA-mediated defences. Mutant analyses indicated that endogenous ABA levels represent an important reservoir that is necessary for effector suppression of plant-inducible innate defence responses and SA synthesis prior to subsequent pathogen-induced increases in ABA. Enhanced susceptibility due to loss of SA-mediated basal resistance is epistatically dominant over acquired resistance due to ABA deficiency, although ABA also contributes to symptom development. We conclude that pathogen-modulated ABA signalling rapidly antagonizes SA-mediated defences. We predict that hormonal perturbations, either induced or as a result of environmental stress, have a marked impact on pathological outcomes, and we provide a mechanistic basis for understanding priming events in plant defence.

Item Type:	Journal Article
Divisions:	Faculty of Science, Engineering and Medicine > Science > Life Sciences (2010- )
Journal or Publication Title:	The Plant Journal
Publisher:	Wiley-Blackwell Publishing Ltd.
ISSN:	0960-7412
Official Date:	2009
Dates:	Date Event 2009 Published
Volume:	59
Number:	3
Page Range:	pp. 375-386
DOI:	10.1111/j.1365-313X.2009.03875.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access

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