Abstract
The psaAB genes, which encode photosystem I reaction center subunit, are the critical target of regulation in environmental responses of at least cyanobacteria. We previously reported that the Rrf2-type transcriptional regulator Slr0846 regulates psaAB expression in Synechocystis sp. PCC 6803. On the other hand, the OmpR-type response regulator RpaB, which is involved in various high-light responses, also binds to the psaAB promoter. Meanwhile, target genes of RpaA, which has strong sequence homology to the RpaB, are unknown. In this study, we examined the binding of His-tagged RpaA to the psaAB promoter by EMSA and DNaseI footprinting assay. It was found that RpaA binds to one of the three RpaB binding motifs in the psaAB promoter, although the binding affinity of RpaA was weaker than that of RpaB. To further study the role of RpaA for the psaAB transcription in vivo, we constructed RpaA deletion and over-expression strains.
