Sensors of abiotic stress in Synechocystis

Abstract

Systematic mutagenesis of histidine kinases in combination with DNA microarraytechnology has allowed us to identify sensors for cold, hyperosmotic stress, sodiumchloride, phosphate, and metal ions in Synechocystis sp. PCC 6803. Hiskinase 33 (Hik33) senses both cold and hyperosmotic stress and regulates the expressionof different sets of genes when cells are exposed to each respective stress.Salt stress is perceived by Hik33, Hik34, and Hik16, each of which regulates theexpression of a different set of genes. Hik7 has been identified as a sensor ofphosphate deficiency. Moreover, manganese deficiency and an excess of nickelions are sensed by Hik27 (ManS) and Hik30 (NrsS), respectively. The genomes ofsix strains of cyanobacteria all include genes for Hik33, Hik34, and Hik7, suggestingthat these three histidine kinases might be important for the perception ofstress in many or even all cyanobacteria.