Abstract
Generally, major constituents of cellular membrane lipids are phospholipids, whereas those of chloroplast membrane lipids in plants are glyceroglycolipids such as monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). When higher plants are exposed to phosphate (Pi) starvation, they decrease a proportion of phospholipids and instead increase the DGDG content in extraplastidic membranes. In Arabidopsis, MGDG synthase (MGD) 2 and MGD3 are highly upregulated by Pi starvation and contribute to the accumulation of DGDG by synthesizing MGDG, a precursor of DGDG. To analyze the regulatory mechanisms of MGD2 expression, in this study, we introduced various truncated promoter sequences of MGD2 fused to its initial 3 codons and β-glucuronidase (GUS) gene into Arabidopsis. Analyses of these transgenic plants revealed two important regions for the MGD2 expression; one is involved in the suppression of MGD2 expression under Pi-sufficient conditions while the other is required for its upregulation under Pi-deficient conditions.
