A Vitamin B12-Based System for Conditional Expression Reveals dksA To Be an Essential Gene in Myxococcus xanthus
A Vitamin B12-Based System for Conditional Expression Reveals dksA To Be an Essential Gene in Myxococcus xanthus
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DOI：
10.1128/jb.01737-08
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发表时间：
2009-05-01
影响因子：
3.2
通讯作者：
Elias-Arnanz, Montserrat
中科院分区：
文献类型：
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作者：
Garcia-Moreno, Diana;Carmen Polanco, Maria;Elias-Arnanz, Montserrat
黄粘球菌是研究多细胞发育和蓝光响应的原核模型系统。先前对这些过程的分析和新基因的表征将受益于一个强大的控制基因表达的系统，这对于这种细菌来说是难以捉摸的。在这里，基于我们最近的发现，我们描述了M. xanthus中基因条件表达的系统，维生素B-12和CarH（一种er型转录抑制因子）共同下调光诱导启动子。利用这个系统，我们证实了M. xanthus编码sigma（54）的rpoN是一个必需基因，正如之前报道的那样。然后我们用ftsZ和dksA测试了它。在大多数细菌中，ftsZ因其在细胞分裂中的作用而至关重要，而dksA的零突变体（其产物通过转录控制rRNA和氨基酸生物合成启动子来调节严格的反应）是可行的，但会产生多效性效应。与rpoN一样，除了携带另一个功能拷贝的merodiploid背景外，不可能在黄豆中删除内源性ftsZ或dksA，这表明它们是必需基因。基于b -12的ftsZ条件表达不足以提供所需的高细胞内ftsZ水平。dksA和rpoN一样，细胞在允许而非限制条件下存活，dksA或sigma的消耗（54）产生丝状的、异常分裂的细胞。因此，dksA就加入了rpoN的行列，成为越来越多的基因，这些基因在许多细菌中是不可缺少的，但在黄原杆菌中却是必不可少的。
Myxococcus xanthus is a prokaryotic model system for the study of multicellular development and the response to blue light. The previous analyses of these processes and the characterization of new genes would benefit from a robust system for controlled gene expression, which has been elusive so far for this bacterium. Here, we describe a system for conditional expression of genes in M. xanthus based on our recent finding that vitamin B-12 and CarH, a MerR-type transcriptional repressor, together downregulate a photoinducible promoter. Using this system, we confirmed that M. xanthus rpoN, encoding sigma(54), is an essential gene, as reported earlier. We then tested it with ftsZ and dksA. In most bacteria, ftsZ is vital due to its role in cell division, whereas null mutants of dksA, whose product regulates the stringent response via transcriptional control of rRNA and amino acid biosynthesis promoters, are viable but cause pleiotropic effects. As with rpoN, it was impossible to delete endogenous ftsZ or dksA in M. xanthus except in a merodiploid background carrying another functional copy, which indicates that these are essential genes. B-12-based conditional expression of ftsZ was insufficient to provide the high intracellular FtsZ levels required. With dksA, as with rpoN, cells were viable under permissive but not restrictive conditions, and depletion of DksA or sigma(54) produced filamentous, aberrantly dividing cells. dksA thus joins rpoN in a growing list of genes dispensable in many bacteria but essential in M. xanthus.