Abstract
Oxidative stress is a major environmental factor for all living organisms. Incubation of the cyanobacterial cells of Synechocystis with 0.25 mM of H2O2 causes dramatic changes in the pattern of gene expression. Expression of about 230 genes encoded in the genome was enhanced and 260 genes were repressed by H2O2. We also found that two histidine kinases, Hik33 and Hik34, and a putative transcription factor were involved in the regulation of H2O2-inducible genes. Hik33 regulated the expression of more than 100 genes and Hik34 regulates that of 20 genes. The transcription factor negatively regulates the expression of a small number of genes. However, the expression of other genes was not regulated by these components. These results suggest that there are at least 4 pathways for signal transduction of oxidative stress in Synechocystis.
