Arabidopsis mutants affecting oxylipin signaling in photo-oxidative stress responses.

Plant oxylipins derive from oxygenation of polyunsaturated fatty acids in thylakoid membranes and oxylipins such as jasmonic acid (JA) and 12-oxo-phytodienoic acid (OPDA) play important roles in adaptation to photo-oxidative stress. OPDA functions both as a JA precursor and as a biologically active signaling molecule that induces expression of a specific set of genes. These genes can be induced by OPDA in the JA-insensitive coronatine insensitive1 (coi1) mutant, suggesting that there is an alternative pathway for OPDA signaling, independent of COI1-dependent JA signaling. However, little is known about OPDA signaling in photo-oxidative stress responses. In this study, we isolated Arabidopsis mutants with constitutively enhanced expression from the OPDA-responsive HsfA2 promoter. We used deletion mapping and complementation analysis to identify one responsible gene as CATALASE2. Our results thus indicate that ROS-producing cellular metabolism links to OPDA signaling.