Transcription of σ54-dependent but not σ28-dependent flagellar genes in Campylobacter jejuni is associated with formation of the flagellar secretory apparatus
Transcription of σ54-dependent but not σ28-dependent flagellar genes in Campylobacter jejuni is associated with formation of the flagellar secretory apparatus
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DOI：
10.1046/j.1365-2958.2003.03731.x
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发表时间：
2003-10-01
影响因子：
3.6
通讯作者：
DiRita, VJ
中科院分区：
文献类型：
--
作者：
Hendrixson, DR;DiRita, VJ
我们进行了空肠弯曲菌鞭毛调控的遗传分析，从中我们阐明了该细菌中鞭毛转录级联的关键部分。为了这项研究，我们开发了一个报告基因系统的C。jejuni中，将astA置于sigma（54）调节的flgDE 2启动子的控制下。空肠菌株81-176。与转座子诱变相结合的astA报告基因融合使我们能够鉴定其中插入废除flgDE 2表达的基因;鉴定的基因在染色体和质粒pVir上。染色体基因中包括编码推定的传感器激酶和sigma（54）依赖性转录激活因子FlgR的基因。此外，我们鉴定了特定的鞭毛基因，包括flhA，flhB，fliP，fliR和flhF，它们也是flgDE 2转录所需的，并且可能位于C.空肠鞭毛转录级联反应。缺失这些基因中的任何一个都会降低flgDE 2和另一种编码次要鞭毛蛋白的sigma（54）依赖性鞭毛基因flaB的转录。编码主要鞭毛蛋白的sigma（28）依赖基因flaA的转录在突变体中基本上不受影响。对flaA转录的进一步检查揭示了显著的sigma（28）非依赖性转录和推定的抗sigma（28）因子FlgM的仅弱抑制活性。我们的研究表明，鞭毛基因的sigma（54）依赖性转录在C。空肠与鞭毛分泌器的形成有关。C语言中的一个关键区别是：空肠杆菌鞭毛转录级联与其他使用σ（28）转录鞭毛基因的细菌相比，在鞭毛装配突变体中显著抑制σ（28）依赖的flaA转录的机制在C.空肠。
We performed a genetic analysis of flagellar regulation in Campylobacter jejuni, from which we elucidated key portions of the flagellar transcriptional cascade in this bacterium. For this study, we developed a reporter gene system for C. jejuni involving astA, encoding arylsulphatase, and placed astA under control of the sigma(54)-regulated flgDE2 promoter in C. jejuni strain 81-176. The astA reporter fusion combined with transposon mutagenesis allowed us to identify genes in which insertions abolished flgDE2 expression; genes identified were on both the chromosome and the plasmid pVir. Included among the chromosomal genes were genes encoding a putative sensor kinase and the sigma(54)-dependent transcriptional activator, FlgR. In addition, we identified specific flagellar genes, including flhA, flhB, fliP, fliR and flhF, that are also required for transcription of flgDE2 and are presumably at the beginning of the C. jejuni flagellar transcriptional cascade. Deletion of any of these genes reduced transcription of both flgDE2 and another sigma(54)-dependent flagellar gene, flaB, encoding a minor flagellin. Transcription of the sigma(28)-dependent gene flaA, encoding the major flagellin, was largely unaffected in the mutants. Further examination of flaA transcription revealed significant sigma(28)-independent transcription and only weak repressive activity of the putative anti-sigma(28) factor FlgM. Our study suggests that sigma(54)-dependent transcription of flagellar genes in C. jejuni is linked to the formation of the flagellar secretory apparatus. A key difference in the C. jejuni flagellar transcriptional cascade compared with other bacteria that use sigma(28) for transcription of flagellar genes is that a mechanism to repress significantly sigma(28)-dependent transcription of flaA in flagellar assembly mutants is absent in C. jejuni.