Essential Role of Digalactosyldiacylglycerol for Photosynthetic Growth in Synechocystis sp. PCC 6803 under High-Temperature Stress
The galactolipid digalactosyldiacylglycerol (DGDG) is present in the thylakoid membranes of oxygenic photosynthetic organisms such as higher plants and cyanobacteria. Recent X-ray crystallographic analysis of protein-cofactor supercomplexes in thylakoid membranes revealed that DGDG molecules are specifically present in the photosystem II (PSII) complex (seven molecules per monomer), suggesting that DGDG molecules play important roles in folding and assembly of subunits in the PSII complex. However, the specific role of DGDG in photosynthesis has not been fully clarified. Recently, we identified the dgdA gene (slr 1508) of Synechocystis sp. PCC 6803 that presumably encodes a DGDG synthase involved in the biosynthesis of DGDG. Disruption of the dgdA gene resulted in a mutant defective in DGDG synthesis. In this study, to clarify the physiological roles of DGDG in photosynthesis, we examined the effects of depletion of DGDG on growth and photosynthetic properties under high-temperature stress using the disruption mutant of dgdA gene.
KeywordsDigalactosyldiacylglycerol High-temperature stress Oxygen-evolving complex Photosystem II Synechocystis sp. PCC 6803
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