Abstract
In the genome of Synechocystis sp. PCC 6803, nine genes for sigma factors have been identified. Among them, the function of the group 3 sigma factors remains to be investigated. To study the role of SigG, we constructed a mutant strain lacking the sigG gene. The incomplete segregation of the sigG mutant strains indicated that this gene is essential. Growth rate of the sigG mutant under standard growth conditions is greatly retarded. We postulated that SigG is involved in the transcription of the sigA gene. Indeed, both mRNA and protein levels of sigA decreased in the mutant. The sigG mutant was sensitive to methyl viologen-induced oxidative stress, indicating that SigG is involved in transcription of oxidative stress genes such as slr1738. Indeed, the induction of slr1738 reduced in the sigG mutant. Our results suggest that sigA and slr1738 are the targets of SigG.
