The response regulator expM is essential for the virulence of Erwinia carotovora subsp carotovora and acts negatively on the sigma factor RpoS (σS)
The response regulator expM is essential for the virulence of Erwinia carotovora subsp carotovora and acts negatively on the sigma factor RpoS (σS)
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DOI：
10.1094/mpmi.1999.12.7.575
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发表时间：
1999-07-01
影响因子：
3.5
通讯作者：
Pirhonen, M
中科院分区：
文献类型：
--
作者：
Andersson, RA;Palva, ET;Pirhonen, M
胡萝卜软腐欧文氏菌胡萝卜亚种（Erwinia carotovora subsp. carotovora）的主要毒力因子是分泌到细胞外的细胞壁降解酶，它们受多种调控机制控制。我们分离出了对烟草毒力降低的转座子突变体。其中一个突变体在一个名为expM的基因上发生突变，本研究对其进行了特征分析。该突变体在体外产生的细胞外酶量略有减少，并且酶的分泌也受到影响。expM的野生型等位基因与一个上游基因（名为expL，功能未知）一起被克隆。对expM基因进行测序，发现它编码的一种蛋白质与大肠杆菌的RssB/SprE蛋白和鼠伤寒沙门氏菌的MviA蛋白相似。这些蛋白质属于一种新型的双组分反应调节因子，在蛋白质水平上对Sigma因子RpoS（σ(S)）的稳定性进行负调控。本研究结果表明，ExpM在胡萝卜软腐欧文氏菌胡萝卜亚种中具有类似的功能。我们还提供证据表明，expM突变体中RpoS的过量产生是毒力表型降低的一个重要因素，并且它在一定程度上导致了在体外观察到的表型。然而，一个expM/rpoS双突变体在细胞外酶的分泌方面仍然受到影响，这表明ExpM除了作用于RpoS外，还作用于其他靶点。
The main virulence factors of Erwinia carotovora subsp. carotovora, the secreted, extracellular cell-wall-degrading enzymes, are controlled by several regulatory mechanisms. We have isolated transposon mutants with reduced virulence on tobacco. One of these mutants, with a mutation in a gene designated expM, was characterized in this study. This mutant produces slightly reduced amounts of extracellular enzymes in vitro and the secretion of the enzymes is also affected. The expM wild-type allele was cloned together with an upstream gene, designated expL, that has an unknown function. The expM gene was sequenced and found to encode a protein with similarity to the RssB/SprE protein of Escherichia coli and the MviA protein of Salmonella typhimurium, These proteins belong to a new type of two-component response regulators that negatively regulate the stability of the Sigma factor RpoS (sigma(S)) at the protein level. The results of this study suggest that ExpM has a similar function in E. carotovora subsp. carotovora, We also provide evidence that the overproduction of RpoS in the expM mutant is an important factor fbr the reduced virulence phenotype and that it partly causes the observed phenotype seen in vitro. However,;an expM/rpoS double mutant is still affected in secretion of extracellular enzymes, suggesting that ExpM in addition to RpoS also acts on other targets.