CONTRIBUTION OF MEMBRANE-LIPIDS TO THE ABILITY OF THE PHOTOSYNTHETIC MACHINERY TO TOLERATE TEMPERATURE STRESS

The contribution of the unsaturation of membrane lipids to the ability of the photosynthetic machinery to tolerate temperature stress was st udied in a transgenic cyano bacterium. Anacystis nidulans R2-SPc was t ransformed with the desA gene, which encodes the Delta(12)-desaturase that desaturates the fatty acids of membrane lipids in Synechocystis P CC6803. The transformant acquired the ability to introduce a second do uble bond into palmitoleic and oleic acids. The transformation enhance d the tolerance of the photosynthetic machinery to chilling stress but it had no detectable effect on the ability to tolerate heat stress. T he transformation itself did not have any effect on photosynthetic act ivity. These results imply that an increase in the unsaturation of mem brane lipids enhances the tolerance of the photosynthetic machinery to ward chilling stress but not toward heat stress and that such an incre ase does not affect photosynthesis within the range of physiological t emperatures.