The alternative sigma factor SigB of Corynebacterium glutamicum modulates global gene expression during transition from exponential growth to stationary phase.
The alternative sigma factor SigB of Corynebacterium glutamicum modulates global gene expression during transition from exponential growth to stationary phase.
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DOI：
10.1186/1471-2164-8-4
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发表时间：
2007-01-04
期刊：
影响因子：
4.4
通讯作者：
Kalinowski, Jorn
中科院分区：
文献类型：
--
作者：
Larisch, Christof;Nakunst, Diana;Huser, Andrea T;Tauch, Andreas;Kalinowski, Jorn
谷氨酸棒杆菌是一种革兰氏阳性土壤细菌，广泛用于工业生产氨基酸。研究转录调控的分子机制具有很大的意义。这些控制机制之一是西格玛因素。C.谷氨酸杆菌ATCC 13032具有七个推定的σ因子编码基因，包括sigA和sigB。sigA基因编码C.谷氨酸并负责管家基因的启动子识别。sigB基因编码非必需的σ因子SigB，该因子在应激反应中具有建议的作用。sigB基因的表达是最高的指数增长和稳定期之间的过渡，当sigA mRNA的量已经下降。通过比较DNA微阵列杂交记录野生型和sigB突变体的全基因组转录谱。这些数据表明，在sigB-熟练的菌株在过渡阶段期间，111个基因的mRNA水平显着变化，而sigB-缺陷型菌株的表达谱仅显示出微小的变化（26个基因）。仅在sigB-proficient菌株中在过渡期表达较高的基因主要属于氨基酸代谢、碳代谢、胁迫防御、膜过程和磷代谢的功能类别。这些基因的转录起始点进行了测定和推导的启动子序列原来是无法区分的共识启动子识别SigA。实时逆转录PCR分析显示，这些基因在生长过程中的表达谱与sigB基因本身的表达谱相似。然而，在sigB突变体中，转录谱类似于编码管家sigma因子的sigA基因。在过渡期，sigB基因表达增强，而sigA mRNA表达量减少。这可能导致在RNA聚合酶核心酶处SigA被SigB取代，并进而导致与过渡期和稳定期相关的基因表达增加，以科普营养限制或伴随的氧化应激。编码抗氧化或保护功能的基因的表达增加也使细胞为即将到来的限制和环境压力做好准备。
Corynebacterium glutamicum is a gram-positive soil bacterium widely used for the industrial production of amino acids. There is great interest in the examination of the molecular mechanism of transcription control. One of these control mechanisms are sigma factors. C. glutamicum ATCC 13032 has seven putative sigma factor-encoding genes, including sigA and sigB. The sigA gene encodes the essential primary sigma factor of C. glutamicum and is responsible for promoter recognition of house-keeping genes. The sigB gene codes for the non-essential sigma factor SigB that has a proposed role in stress reponse. The sigB gene expression was highest at transition between exponential growth and stationary phase, when the amount of sigA mRNA was already decreasing. Genome-wide transcription profiles of the wild-type and the sigB mutant were recorded by comparative DNA microarray hybridizations. The data indicated that the mRNA levels of 111 genes are significantly changed in the sigB-proficient strain during the transition phase, whereas the expression profile of the sigB-deficient strain showed only minor changes (26 genes). The genes that are higher expressed during transition phase only in the sigB-proficient strain mainly belong to the functional categories amino acid metabolism, carbon metabolism, stress defense, membrane processes, and phosphorus metabolism. The transcription start points of six of these genes were determined and the deduced promoter sequences turned out to be indistinguishable from that of the consensus promoter recognized by SigA. Real-time reverse transcription PCR assays revealed that the expression profiles of these genes during growth were similar to that of the sigB gene itself. In the sigB mutant, however, the transcription profiles resembled that of the sigA gene encoding the house-keeping sigma factor. During transition phase, the sigB gene showed an enhanced expression, while simultaneously the sigA mRNA decreased in abundance. This might cause a replacement of SigA by SigB at the RNA polymerase core enzyme and in turn results in increased expression of genes relevant for the transition and the stationary phase, either to cope with nutrient limitation or with the accompanying oxidative stress. The increased expression of genes encoding anti-oxidative or protection functions also prepares the cell for upcoming limitations and environmental stresses.