A very early event of photoinactivation of photsystem II at low temperature

Abstract

When the photosynthetic machinery is irridiated by strong light the photosystem II (PSII) complex is photodamaged although PSII is repaired by a process which requires protein synthesis. We investigated the photoinactivation and recovery of PSII at low temperatures in Synechocystis sp. PCC 6803 cells and a mutant defective in unsaturation of membrane lipids. When the cells were exposed to light of 2000 µE m-2 s-2 at 0°C and then were incubated at 34°C in darkness, approximately 50% of the PSII activity recovered after 60 min. This recovery occurred in the presence of lincomycin which inhibits translation of D1 protein suggesting that the recovery in darkness did not involve synthesis de novo of proteins. This observation together with other results lead us to hypothesize of the involvement of an intermediately photoinactivated PSII prior to the stable photodamaged PSII, which is currently well discussed.