THE UNSATURATION OF MEMBRANE-LIPIDS STABILIZES PHOTOSYNTHESIS AGAINSTHEAT-STRESS

The effect of the unsaturation of glycerolipids of thylakoid membranes on the heat tolerance of the photosynthetic evolution of oxygen was s tudied in vivo by mutation and transformation of fatty-acid desaturase s in the cyanobacterium Synechocystis PCC6803. The experimental result s indicate that elimination of dienoic lipid molecules decreases, to a small but distinct extent, the heat tolerance of photosynthetic oxyge n evolution, but that elimination of trienoic lipid molecules has no e ffect on the heat tolerance. This conclusion contrasts with the previo us hypothesis that the heat tolerance of photosynthesis is enhanced up on an increase in the level of saturation of membrane lipids. It is al so shown that light does not affect the nature of the effect of lipid unsaturation on the heat tolerance of photosynthesis.