Abstract
The glyceroglycolipid is the major lipid in plastid membrane. The three glyceroglycolipids are monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG). SQDG is synthesized by UDP-sulfoquinovose synthase (SQD1) and SQDG synthase (SQD2). Recently, it was reported that SQD1 formed a complex with ferredoxin-dependent glutamate synthase (Fd-GOGAT) in spinach chloroplasts, suggesting the possible cross-talk between the sulfolipid biosynthesis and nitrogen assimilation. In this study, we analyzed the lipid composition and the expression of the genes involved in SQDG biosynthesis in Arabidopsis thaliana knock-out mutants of Fd-GOGAT, glu1 and glu2. In the both mutants, SQDG level was lower than that in wild-type under normal growth conditions. Expression of most of the genes involved in SQDG biosynthesis was downregulated in glu2, whereas, in glu1, only the expression of APS reductase was decreased. From these results, it was suggested that Fd-GOGAT directly affects SQDG biosynthesis by interacting with SQD1, or glutamate biosynthesis transcriptionally affects the expression of the genes involved in SQDG biosynthesis.
