Huckauf Jana, Nomura Chris, Forchhammer Karl, Hagemann Martin
Universität Rostock, FB Biologie, Institut für Molekulare Physiologie und Biotechnologie, Doberaner Str. 143,D-18051 Rostock, Germany1.
Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA 16802, USA2.
Microbiology (Reading). 2000 Nov;146 ( Pt 11):2877-2889. doi: 10.1099/00221287-146-11-2877.
In the complete genome sequence of the cyanobacterium SYNECHOCYSTIS: sp. strain PCC 6803 [Kaneko et al. (1996 ). DNA Res 3, 109-136] genes were identified encoding putative group 3 sigma-factors SigH (Sll-0856), SigG (Slr-1545) and SigF (Slr-1564) and the regulatory protein RsbU (Slr-2031). Mutations in these genes were generated by interposon mutagenesis to study their importance in stress acclimation. For the genes sigH, sigF and rsbU, the loci segregated completely. However, attempts to mutagenize the sigG locus resulted in merodiploids. Under standard growth conditions only minor differences were detected between the mutants and wild-type. However, cells of the RsbU mutant showed a clear defect in regenerating growth after a nitrogen- and sulphur-starvation-induced stationary phase. After applying salt, heat and high-light shocks, stress protein synthesis was analysed by means of one- and two-dimensional electrophoresis. Cells of the SigF mutant showed a severe defect in the induction of salt stress proteins. Although the acclimation to moderate salt stress up to 684 mM NaCl was not significantly changed in this mutant, its ability to acclimate to higher concentrations of NaCl was reduced. Northern blot experiments showed a constitutive expression of the rsbU and sigF genes. The expression of the sigH gene was found to be stress-stimulated, particularly in heat-shocked cells, whilst that of sigG was transiently decreased under stress conditions. Possible functions of these regulatory proteins in stress acclimation of Synechocystis cells are discussed.
在蓝藻集胞藻PCC 6803株的全基因组序列中[金子等人（1996年）。《DNA研究》3，109 - 136]，鉴定出了编码假定的3组sigma因子SigH（Sll - 0856）、SigG（Slr - 1545）和SigF（Slr - 1564）以及调节蛋白RsbU（Slr - 2031）的基因。通过插入诱变产生这些基因的突变体，以研究它们在应激适应中的重要性。对于sigH、sigF和rsbU基因，位点完全分离。然而，诱变sigG位点的尝试产生了部分二倍体。在标准生长条件下，突变体和野生型之间仅检测到微小差异。然而，RsbU突变体的细胞在氮和硫饥饿诱导的静止期后再生生长方面表现出明显缺陷。施加盐、热和高光冲击后，通过一维和二维电泳分析应激蛋白合成。SigF突变体的细胞在盐应激蛋白的诱导方面表现出严重缺陷。尽管该突变体对高达684 mM NaCl的中等盐应激的适应能力没有显著变化，但其适应更高浓度NaCl的能力降低。Northern印迹实验表明rsbU和sigF基因组成型表达。发现sigH基因的表达受到应激刺激，特别是在热休克细胞中，而sigG的表达在应激条件下短暂下降。讨论了这些调节蛋白在集胞藻细胞应激适应中的可能功能。
