Polar Lipid Composition of a Plastid Ribosome-Deficient Barley Mutant

Abstract

Green and white leaves of the barley mutant line `albostrians' were compared for their polar lipid content and fatty acid composition. The mutant plastids of the white leaves have a double-layered envelope, but in contrast with the normal chloroplasts, lack 70 S ribosomes and thylakoids. In the green leaves, the amount of monogalactosyldiacylglycerol (MGDG) consistently exceeds the amount of digalactosyldiacylglycerol (DGDG) and the amount of galactolipids exceeds the amount of phospholipids. In contrast, in white leaves the amount of DGDG exceeds the amount of MGDG and the amount of phospholipids exceeds the amount of galactolipids. In white leaves, the galactolipid composition reflects the plastid envelope composition which is rich in DGDG, whereas in green leaves the galactolipid composition reflects the thylakoid composition which is rich in MGDG. These results demonstrate the likelihood that all the enzymes involved in galactolipid, sulfolipid and fatty acid synthesis are coded by the nuclear genome.