GENETIC ENHANCEMENT OF THE ABILITY TO TOLERATE PHOTOINHIBITION BY INTRODUCTION OF UNSATURATED BONDS INTO MEMBRANE GLYCEROLIPIDS

Strong light leads to damage to photosynthetic machinery, particularly at low temperatures, and the main site of the damage is the D1 protei n of the photosystem II (PSII) complex. Here we describe that transfor mation of Synechococcos sp. PCC 7942 with the desA gene for a Delta 12 desaturase increased unsaturation of membrane lipids and enhanced tol erance to strong light. To our knowledge, this is the first report of the successful genetic enhancement of tolerance to strong light. Analy sis of the light-induced inactivation and of the subsequent recovery o f the activity of the PSII complex revealed that the recovery process was markedly accelerated by the genetic transformation. Labeling exper iments with [S-35]L-methionine also revealed that the synthesis of the D1 protein de novo at low temperature, which was a prerequisite for t he restoration of the PSII complex, was much faster in the transformed cells than in the wild-type cells. These findings demonstrate that th e ability of membrane lipids to desaturate fatty acids is important fo r the photosynthetic organisms to tolerate strong light, by accelerati ng the synthesis of the D1 protein de novo.