| Recently, soil salinization caused by human activities including the usage ofchemical fertilizers results in decreasing the crop yield. The unicellularcyanobacterium Synechocystis sp. strain PCC6803(hereafter referred toSynechocystis6803) is not only a model organism for photosynthesis research, butalso an ideal experimental material for studying the action mechanism underlying saltstress conditions. Recently, although a variety of significant results have beenobtained, such as the identification of the Hik-Rre two-component system, the Ser/Thr kinase, as well as factor. However, the studies of the action mechanismunderlying salt stress are far from complete, and many genes involving in salt signaltransduction pathways have not been identified.First of all, this thesis identified a high-salt-sensitive mutant (Δm1) by screeningthe transposon mutant library of Synechocysis6803; and futher identified itshomologous gene, m2, using sequence analysis method. Secondly, the results of thisthesis indicated that the transcription levels of m1and m2genes gradually increasedwith the extension of time of salt treatment by using RT-PCR method. However, suchincrease did not occur in the presence of sorbitol or both Na+and Ca2+. We thereforeconclude that the genes of m1and m2are specific to the response to the high-salttreament. Thirdly, this thesis found that the mutation of m1and m2genes specificallyinhibited the transcription of ggpS gene by constructing and analyzing the Δm1, Δm2,and Δm1/m2mutants, and rarely that of other genes identified in the salt signaltransduction pathway. Finally, this thesis porposed the action mechanism of m1and m2genes underlying salt stress on the basis of the results obtained in the present studyand from previous knowledge. The salt signal sensed by Hik34and SpkG causes theexpression of m1and m2genes that help in expressing the ggpS gene to produce themetabolites glucosylglycerol (GG), thereby alleviating the damage of salt stress. |
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