Abstract
Jasmonic acid (JA) is a plant hormone that modulates anther dehiscence, fruit ripening, and plant resistance to insects and pathogens. From the research of the Arabidopsis mutant defective in anther dehiscence1 (dad1), we found that the DAD1 protein is a chloroplastic phospholipase A1 that catalyzes the initial step of JA biosynthesis. The JA amount in young flower buds of the dad1 mutant was decreased to one fifth of the wild-type level, whereas comparable amounts of JA were detected in wounded rosette leaves of both dad1 mutant and wild type, indicating that additional lipolytic enzymes other than DAD1 must be present to participate in the wound induction of JA biosynthesis.
So we found six DAD1-like lipases (DAL1-6) including predicted transit peptides, and made dad1 dal1 dal2 dal3 dal4 dal6 sextuple mutant. We quantified the JA level in wounded rosette leaves and flower bud clusters of sextuple mutant plants, and found that they were considerably decreased as compared with those of wild-type plants. These results indicate that DAD1 and DALs are contributed to JA biosynthesis both in wounded leaves and in flower buds.
