The <i>DEFECTIVE IN ANTHER DEHISCENCE1</i> 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

TLDR

A model is presented in which jasmonic acid synthesized in stamen filaments regulates water transport in stamens and petals. The DAD1 gene was identified by T‑DNA tagging and encodes a chloroplastic phospholipase A1 with a putative N‑terminal transit peptide and conserved lipase active‑site motif. The dad1 mutant shows defective anther dehiscence, pollen maturation, and flower opening, which are rescued by exogenous jasmonic acid or linolenic acid; DAD1 hydrolyzes phospholipids sn‑1‑specifically, initiates jasmonic acid biosynthesis, and its expression is restricted to stamen filaments.

Abstract

The Arabidopsis mutant defective in anther dehiscence1 (dad1) shows defects in anther dehiscence, pollen maturation, and flower opening. The defects were 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 characteristic to a putative N-terminal transit peptide and a conserved motif found in lipase active sites. DAD1 protein expressed in Escherichia coli hydrolyzed phospholipids in an sn-1–specific manner, and DAD1–green fluorescent protein fusion protein expressed in leaf epidermal cells localized predominantly in chloroplasts. These results indicate that the DAD1 protein is a chloroplastic phospholipase A1 that catalyzes the initial step of JA biosynthesis. DAD1 promoter::β-glucuronidase analysis revealed that the expression of DAD1 is restricted in the stamen filaments. A model is presented in which JA synthesized in the filaments regulates the water transport in stamens and petals.