ISOLATION AND CHARACTERIZATION OF AN ARABIDOPSIS MUTANT DEFICIENT IN THE THYLAKOID LIPID DIGALACTOSYL DIACYLGLYCEROL

The galactolipids monogalactosyl and digalactosyl diacylglycerol occur in all higher plants and are the predominant lipid components of chlo roplast membranes, They are thought to be of major importance to chlor oplast morphology and physiology, although direct experimental evidenc e is still lacking, The enzymes responsible for final assembly of gala ctolipids are associated with the envelope membranes of plastids, and their biochemical analysis has been notoriously difficult, Therefore, we have chosen a genetic approach to study the biosynthesis and functi on of galactolipids in higher plants, We isolated a mutant of Arabidop sis that is deficient in digalactosyl diacylglycerol by directly scree ning a mutagenized M(2) population for individuals with altered leaf l ipid composition. This mutant carries a recessive nuclear mutation at a single locus designated dgd1. Backcrossed mutants show stunted growt h, pale green leaf color, reduced photosynthetic capability, and alter ed thylakoid membrane ultrastructure.