729–739 Defects in Allene Oxide Synthase and 12-Oxa-Phytodienoic Acid Reductase Alter the Resistance to Pseudomonas syringae and Botrytis cinerea

Jasmonic acid and its methyl ester are signalling molecules involved in regulating development and stress responses in plants. 12-Oxo-phytodienoic acid, a precursor in jasmonic acid biosynthesis, is also biologically active. Both oxylipins accumulate after pathogen infection. To understand the function of 12-oxo-phytodienoic acid vs. jasmonic acid in plant pathogen interactions, the susceptibility of the dde2 mutant, defective in 12-oxo-phytodienoic acid and jasmonic acid biosynthesis and the opr3 mutant, which synthesizes 12-oxo-phytodienoic acid but not jasmonic acid was investigated. dde2 and opr3 were more resistant to Pseudomonas syringae. The effect was stronger in the dde2 mutant as in opr3 indicating that both oxylipins regulate pathogen resistance to P. syringae. dde2 was more susceptible to Botrytis cinerea suggesting that 12-oxophytodienoic acid is important in mediating the defence against B. cinerea. Expression of Pr1 and Pr2 was increased in both mutants after mock infiltration but not or only slightly enhanced after P. syringae infection