Abstract
Phototrophic organisms respond to photooxidative stresses as well as normal stresses. In this talk, I summarize transcriptional regulation that responds to the various photooxidative stresses. Based on microarray analyses and functional characterization, we identified three photooxidative stress-responsive regulons, i.e. Slr1738(PrxR)–sll1621(prxA), Sll0088–slr0074, and Slr1245–sll1161. Of these, Slr1738 is a Zn and Fe-binding regulator that recognizes redox changes. Sll0088 coordinates FeS cluster to recognize redox changes. We also identified LexA regulation in Synechocystis. Generally, LexA is the single strand DNA-activated protease and regulates gene expression. But we found that LexA lost protease activity at least in Synechocystis. Finally, we recently identified IscR homolog in Synechocystis and many cyanobacteria. It is shown that IscR homolog is essential for expression of PSI genes. Based on these findings, we will discuss general view of responses to various photooxidative stresses.
