Abstract
We have been identified that a histidine kinase, Hik33, is involved in the regulation of gene expression under cold stress, hyperosmotic stress and high-light stress in Synechocysrtis sp. PCC 6803. Hik33 regulates different sets of genes under various conditions, together with common stress-inducible genes, suggesting that Hik33 might perceive various stimuli and sort the signal to regulate the expression of different sets of genes. To investigate mechanisms of signal sorting by Hik33, we performed yeast-two-hybrid screening and identified a gene encoding a small hypothetical protein (ssl3451). The mutation of the ssl3451 gene increased basal levels of expression of the Hik33-regulated stress-inducible genes even under non-stressed conditions and also decreased the induction of gene expression under stress conditions. These results suggest that the small protein might be associated with Hik33 and be involved in the regulation of activities of Hik33.
