The DEFECTIVE IN ANTHER DEHISCENCE1 gene encodes a novel phospholipase A1 catalyzing the initial step of jasmonic acid biosynthesis, which synchronizes pollen maturation, anther dehiscence, and flower opening in Arabidopsis

The Arabidopsis mutant defective in anther dehiscence1 (dad1) shows defects in anther dehiscence, pollen maturation, and flower opening. The defects w ere rescued by the exogenous application of jasmonic acid (JA) or linolenic acid, which is consistent with the reduced accumulation of JA in the dad1 flower buds. We identified the DAD1 gene by T-DNA tagging, which is charact eristic to a putative N-terminal transit peptide and a conserved motif foun d in lipase active sites. DAD1 protein expressed in Escherichia coli hydrol yzed phospholipids in an sn-1-specific manner, and DAD1-green fluorescent p rotein fusion protein expressed in leaf epidermal cells localized predomina ntly in chloroplasts. These results indicate that the DAD1 protein is a chl oroplastic phospholipase All that catalyzes the initial step of JA biosynth esis. DAD1 promoter::beta -glucuronidase analysis revealed that the express ion of DAD1 is restricted in the stamen filaments. A model is presented in which JA synthesized in the filaments regulates the water transport in stam ens and petals.