Sensors of Environmental Stress

组氨酸激酶（Hik）和反应调节因子（Rre）构成双组分系统，是原核生物和部分真核生物的信号感知/转导途径。像植物一样进行氧光合作用的蓝藻藻（synnechocystis sp. PCC 6803）含有47个Hiks基因和45个Rres基因。除了Hiks和Rres的3个基因外，我们成功地对这些基因进行了突变，并构建了Hiks和Rres的突变文库。利用cDNA微阵列对不同胁迫条件下基因的全基因组表达进行文库筛选，得到以下结果：0.5 M山梨醇引起的高渗胁迫诱导246个基因表达。利用cDNA芯片技术筛选上述高渗胁迫诱导基因的突变文库，发现60%的高渗胁迫诱导基因受Hik33/Rre31、Hik16/Hik41/Rre17、Hik34/Rre1、Hik2/Rre1和Hik10/Rre3 5个双组分系统控制。其余40%的高渗应激诱导基因受尚未确定的信号转导途径控制。0.5 M NaCl胁迫诱导了294个基因的表达。通过基因芯片技术对上述盐胁迫诱导基因表达的突变文库进行筛选，发现70%的盐胁迫诱导基因与高渗胁迫诱导基因一样受5个双组分系统的控制。然而，在盐胁迫和高渗胁迫下，个体Hik/Rre双组分系统下的基因是不同的。其余30%的盐胁迫诱导基因受尚未确定的信号转导途径控制。

Histidine kinase (Hik) and response regulator (Rre) constitute the twp-component system that is a signal perception/transduction pathway in prokaryotes and some eukaryotes. The cyanobacterium Synechocystis sp. PCC 6803, which performs oxygenic photosynthesis like plants, contains 47 genes for Hiks and 45 genes for Rres. We mutated these genes successfully, except three genes for Hiks and three genes for Rres, and constructed mutant libraries of Hiks and Rres. By screening the libraries by genome-wide expression of genes under various stress conditions with cDNA microarrays, we obtained the following results.Hyperosmotic stress, due to 0.5 M sorbitol, induced the expression of 246 genes. Screening of the above-mentioned mutant libraries with respect to the hyperosmotic stress-inducible expression of genes by the cDNA microarray method revealed that 60% of the hyperosmotic stress-inducible genes are under control of five two-component systems, namely, Hik33/Rre31, Hik16/Hik41/Rre17, Hik34/Rre1, Hik2/Rre1, and Hik10/Rre3. Remaining 40% of the hyperosmotic stress-inducible genes are under control of as-yet unidentified signal-transducing pathways.Salt stress, due to 0.5 M NaCl, induced the expression of 294 genes. Screening of the above-mentioned mutant libraries with respect to the salt stress-inducible expression of genes by the cDNA microarray method revealed that 70% of the salt stress-inducible genes are under control five two-component systems as in the case of hyperosmotic stress-inducible genes. However, genes under the individual Hik/Rre two-component systems are different between the salt stress and hyperosmotic stress. Remaining 30% of the salt stress-inducible genes are under control of as-yet unidentified signal-transducing pathways.