Igarashi Takao, Setlow Peter
Department of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, CT 06030-3305, USA.
J Bacteriol. 2006 Jun;188(11):4131-6. doi: 10.1128/JB.00265-06.
The gerA, gerB, and gerK operons, which encode germinant receptors in spores of Bacillus subtilis, were transcribed only in sporulation, and their mRNA levels peaked initially approximately 3 h before the initiation of accumulation of the spore's dipicolinic acid. After a rapid fall, levels of these mRNAs peaked again approximately 5 h later. In one wild-type strain (PS832), gerA mRNA was the most abundant, with levels of gerB and gerK mRNAs approximately 50% of that of gerA mRNA, whereas gerB mRNA was the most abundant in another wild-type strain (PY79). The synthesis of gerK mRNA in sporulation was abolished by loss of the forespore-specific RNA polymerase sigma factor, sigma(G), and induction of sigma(G) synthesis in vegetative cells led to synthesis of gerK mRNA. SpoVT, a regulator of sigma(G)-dependent gene expression, repressed gerK expression. The gerK promoter showed sequence similarities to sigma(G)-dependent promoters, and deletion of elements of this putative promoter abolished gerK expression in sporulation.
编码枯草芽孢杆菌孢子中萌发受体的gerA、gerB和gerK操纵子仅在孢子形成过程中被转录，且它们的mRNA水平最初在孢子中吡啶二羧酸积累开始前约3小时达到峰值。在快速下降后，这些mRNA水平约5小时后再次达到峰值。在一个野生型菌株（PS832）中，gerA mRNA最为丰富，gerB和gerK mRNA的水平约为gerA mRNA的50%，而在另一个野生型菌株（PY79）中gerB mRNA最为丰富。孢子形成过程中gerK mRNA的合成因前芽孢特异性RNA聚合酶σ因子σ（G）的缺失而被消除，在营养细胞中诱导σ（G）的合成导致gerK mRNA的合成。SpoVT是σ（G）依赖性基因表达的调节因子，可抑制gerK的表达。gerK启动子与σ（G）依赖性启动子具有序列相似性，该假定启动子元件的缺失消除了孢子形成过程中gerK的表达。
