Abstract
We previously reported that regulation of the suf operon by SufR, which is an Fe-S cluster binding redox sensor. In Escherichia coli, the suf operon is regulated by another transcription factor IscR which carries Fe-S cluster. IscR homologues are found in many cyanobacteria, but critical cysteine residues are not conserved. Here, we report the role of iscR homolog (slr0846) in Synechocystis sp. PCC 6803. DNA microarray analysis of a slr0846 disruptant showed marked decrease in expression of psaAB. Consistently, the mutants exhibit lower PSI/PSII ratio and decreased chlorophyll content. Growth of the mutants was retarded under normal light conditions and severely suppressed under high light conditions. These results suggested that the Slr0846 is involved in regulation of PSI transcript levels. To detect direct interaction of Slr0846 with the psaAB promoter, we are now doing gel shift assays. We also report a suppression mutation that recovers expression of psaAB.
