Abstract
Previously we found that the promoter activities of PSI genes were clearly regulated in response to changes in light intensity in Synechocystis sp. PCC 6803. To identify factors involved in the transcriptional regulation of PSI genes, we screened for mutants with aberrant psaA promoter activities by introducing transposon-mutagenized cosmid library into the strain harboring PpsaA-luxAB chimeric construct. To date, 49 mutagenized cosmids covering the half of the whole genome have been assayed, and we isolated 10 transposon-inserted mutants showing high luminescence under low light. Among them, mutants of slr0609, sll1531 and slr0551 actually showed higher psaA transcript levels than the control strain under low light. psaD and psaF genes were also up-regulated, whereas accumulation of psbA transcript was not affected in these mutants. Now, we characterize the phenotype of the specific targeted inactivation mutants of these ORFs.
