Direct Evaluation of Effects of Fatty-Acid Unsaturation on the Thermal Properties of Photosynthetic Activities, as Studied by Mutation and Transformation of Synechocystis PCC6803

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Glycerolipids of thylakoid membranes isolated from the cyanobacterium Synechocystis PCC6803 contained high levels of dienoic and trienoic C_<18> fatty acids, in addition to saturated and monoenoic C_<18> fatty acids. A mutant C_<16>(Fad12) of this cyanobacterium was defective in the desaturation of C_<18> fatty acids at the Δ^<12> position, and its thylakoid membranes lacked trienoic acids and contained a very reduced level of dienoic acids. A derivative strain of Fad12 (Fad12/desA), which had been transformed with a gene for desaturation at the Δ^<12> position, fully recovered the ability to desaturate the fatty acids in the glycerolipids of thylakoid membranes. The thermal properties of the photosynthetic activities of the mutant and the transformant were compared with those of the wild-type strain. Despite great diversity in the extent of unsaturation of fatty acids between the wild-type, Fad12, and Fad12/desA strains, no significant differences were found either in the temperature dependence of photosynthesis or in the heat stability of photosynthetic, photosystem II and photosystem I activities. These results demonstrate that the trienoic fatty acids and, probably, the dienoic acids of the lipids in the thylakoid membrane do not affect the thermal properties of the above-mentioned activities of photosynthesis.
日本植物生理学会の論文