Abstract
Trienoic fatty acids (TAs) are the most abundant fatty acid species constituting the plant membrane lipids. They serve as the precursor of jasmonic acid (JA), the key regulator of defense responses against wounding. Arabidopsis FAD7 encodes a plastidial isozyme of ω-3 desaturase, which catalyzes the production of TAs. Expression of the FAD7 is greatly induced by wounding. The site of the induction, however, is strictly limited to the local damaged tissues. To visualize such a highly tissue-specific pattern of FAD7 expression, we constructed a transgenic line of Arabidopsis carrying the FAD7 promoter fused to the firefly luciferase gene. By screening the M2 population of this transgenic line, we isolated a mutant showing enhanced bioluminescence in response to wounding. The gene responsible for the mutation encoded a novel membrane-bound protein likely localized to chloroplasts. Epistasis of this regulatory protein in relation to JA and its major signaling components will be discussed.
