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

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:: ␤ -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.

The Arabidopsis male-sterile mutant dde2-2 is defective in the ALLENE OXIDE SYNTHASE gene encoding one of the key enzymes of the jasmonic acid biosynthesis pathway

“…An identical phenotype has been described for several male-sterile Arabidopsis mutants, namely the triple mutant fad3-2fad7-1fad8 (McConn and Browse 1996), the coronatine-insensitive mutant coi1 (Feys et al 1994;Xie et al 1998) and the JA biosynthesis mutants opr3/dde1 (Sanders et al 2000;Stintzi and Browse 2000) and dad1 (Ishiguro et al 2001). Detailed investigations of the dde1/opr3 and dad1 mutant phenotypes by Sanders et al (2000) and Ishiguro et al (2001) did not reveal any differences between mutant and wild-type anther development until the stage just before flower opening.…”

“…Detailed investigations of the dde1/opr3 and dad1 mutant phenotypes by Sanders et al (2000) and Ishiguro et al (2001) did not reveal any differences between mutant and wild-type anther development until the stage just before flower opening. Thus, the developmental processes in the mutants are indistinguishable from those in the wild type prior to dehiscence.…”

“…More recently, mutants defective in the JA biosynthesis pathway have been found. The DEFEC-TIVE IN ANTHER DEHISCENCE1 gene (DAD1) encodes a phospholipase A1 catalyzing the initial step of JA biosynthesis (Ishiguro et al 2001), whereas the opr3/ dde1 mutant is defective in the OPDA-reductase downstream in the JA biosynthesis pathway (Sanders et al 2000;Stintzi and Browse 2000). All JA mutants exhibit a similar characteristic phenotype with reduced elongation of the filaments, delayed anther dehiscence and reduced pollen viability resulting in male sterility.…”

“…More recently, several large screens of T-DNA and ethyl methanesulfonate (EMS)-mutagenised Arabidopsis populations led to the identification of male-sterile lines and, subsequently, to the isolation of the mutated genes (e.g. Sanders et al 1999), among them genes involved in the jasmonic acid (JA) biosynthesis pathway (Sanders et al 2000;Stintzi and Browse 2000;Ishiguro et al 2001).…”

Arabidopsis mutants affected in the transcriptional control of allene oxide synthase, the enzyme catalyzing the entrance step in octadecanoid biosynthesis

“…Genetic evidence further supports this conclusion: the dad1 mutant is deficient in a phospholipase A1, which is specifically expressed in filaments and required for JA synthesis in this organ. The mutant produces short filaments and carries a structural defect in fertility (Ishiguro et al 2001) rather similar to cas1. However, dad1 plants produce normal levels of JA upon wounding in leaves.…”