Suppression by ABA of salicylic acid and lignin accumulation and the expression of multiple genes, in Arabidopsis infected with Pseudomonas syringae pv. tomato
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Abscisic acid (ABA) has been implicated in determining the outcome of interactions between many plants and their pathogens. We had previously shown that increased concentrations of ABA within leaves of Arabidopsis induced susceptibility towards an avirulent strain of Pseudomonas syringae pathovar (pv.) tomato. We now show that ABA induces susceptibility via suppression of the accumulation of components crucial for a resistance response. Lignin and salicylic acid concentrations in leaves were increased during a resistant interaction but reduced when plants were treated with ABA. The reduction in lignin and salicylic acid production was independent of the development of the hypersensitive response (HR), indicating that, in this host-pathogen system, HR is not required for resistance. Genome-wide gene expression analysis using microarrays showed that treatment with ABA suppressed the expression of many defence-related genes, including those important for phenylpropanoid biosynthesis and those encoding resistance-related proteins. Together, these results show that resistance induction in Arabidopsis to an avirulent strain of P. syringae pv. tomato is regulated by ABA.
KeywordsABA Microarray Disease resistance Arabidopsis thaliana Salicylic acid Lignin
We would like to thank the staff of the Victorian Microarray Technology Consortium, La Trobe University who assisted with the collection of ATH1 GeneChip data and Deakin University for provision of a post graduate scholarship to PGM and Central Research Grant Scheme funding to DMC.
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