Transcriptome analysis of the microalgae Synechocystis sp. PCC 6803 and mechanisms of photoinhibition tolerance under extreme high light conditions

To investigate acclimation mechanisms employed under extreme high light conditions, gene expression analysis was performed using the model microalgae Synechocystis sp. PCC 6803 (PCC 6803) cultured under various light intensities. From the low to the mid light conditions, the expression of genes related to light harvesting systems was repressed, whereas that of CO2 fixation and of D1 protein turnover-related genes was induced. Gene expression data also revealed that the down-regulation of genes related to flagellum synthesis (pilA2), pyridine nucleotide transhydrogenase (pntA and pntB), and sigma factor (sigA and sigF) represents acclimation mechanisms of PCC 6803 under excessive high light conditions. The gene expression in Synechocystis sp. PCC 6803 was analyzed following culture at 30, 50, 300, 1000, 1100, and 1300 μmol m-2 s-1. Three independent experiments were performed under each light intensity. To check the repeatability, some RNA samples are analyzed in three microarraies.