Abstract
To investigate high light acclimation mechanism, we isolated &Deltasll1961 in the cyanobacterium Synechocystis PCC 6803 which showed different chlorophyll fluorescence kinetics from WT under high light condition. We investigated the photosynthetic characteristics of the mutant using pulse amplitude modulation fluorometer. Just after exposure to actinic light, the rise of fluorescence intensity was slower in &Deltasll1961 grown under high light condition, indicating that the activity of PSI might increase. To determine whether photosystem stoichiometry is different between WT and &Deltasll1961, we examined fluorescence emission spectra at 77K. While the ratio of PSI to PSII decreased in WT upon the acclimation to high light, it was constant in &Deltasll1961. Therefore, we conclude &Deltasll1961 cannot decrease the amounts of PSI during exposure to high light. To examine the involvement of Sll1961 in the modulation of photosystem stoichiometry, we are searching for the downstream targets of Sll1961 using DNA microarray.
