title: Suppression by ABA of salicylic acid and lignin accumulation and the expression of multiple genes, in Arabidopsis infected with Pseudomonas syringae pv. tomato.
abstract: 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.
authors.affiliation: School of Life and Environmental Sciences, Deakin University, Geelong campus at Waurn Ponds, Geelong, Victoria 3217, Australia.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Mohr
authors.forename: David M
authors.initials: DM
authors.lastname: Cahill
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics* / Q000382:microbiology; D015870:Gene Expression / Q000187:drug effects; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant; D008031:Lignin / Q000032:analysis / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010935:Plant Diseases / Q000235:genetics*; D044224:Pseudomonas syringae; D020156:Salicylic Acid / Q000032:analysis / Q000378:metabolism*
chemical_list: D000040:Abscisic Acid; D008031:Lignin; D020156:Salicylic Acid