Lack of digalactosyldiacylglycerol increases the sensitivity of Synechocystis sp. PCC 6803 to high temperature stress

Abstract

We examined the effect of lack of digalactosyldiacylglycerol (DGDG) on the heat sensitivity to photosynthetic machinery using a dgdA mutant of Synechocystis sp. PCC6803 that is defective in the biosynthesis of DGDG. The mutant cells showed normal growth under low light at 30^oC. However, the growth of mutant cells was retarded compared to wild-type cells when the growth temperature was changed to 38^oC. The growth retardation at 38^oC became more apparent under high light. Experiments on photoinhibition of photosynthesis showed that both photodamage and repair processes of photosynthesis were severely affected at 38^oC in the mutant cells compared to the wild-type cells. The oxygen-evolution activity of mutant cells was more easily inactivated by dark-incubation at 38^oC and by incubation with hydroxylamine than that of wild-type cells. These results suggest that the decreased stability of oxygen-evolution system in mutant cells results in the increased sensitivity to light and high temperature stresses.