Abstract
Monogalactosyldiacylglycerol (MGDG) is the most abundant lipid in thylakoid membrane of chloroplasts. It constitutes for almost 50% of the total thylakoid lipids. MGDG is synthesized by MGDG synthase in chloroplast envelope. Since MGDG is so abundant in chloroplast and a second major galactolipid, digalactosyldiacylglycerol is synthesized from MGDG, biosynthesis of MGDG is one of the most important steps to construct chloroplast.
In Arabidopsis, three genes for MGDG synthase are encoded in the genome. Among them, MGD1 is localized in inner envelope and mainly contributes development of thylakoid membrane. Recently, we isolated a T-DNA tag mutant of the MGD1 gene. Unexpectedly, homozygous mutants showed severe defects in not only greening process but also early stage of embryo development. MGDG content of the mutant was less than 10% of wild type. Defect of MGD1 gene also resulted in large deformation of the plastid structure, demonstrating the importance in proper chloroplast development.
