Type IV pili function upstream of the Dif chemotaxis pathway in Myxococcus xanthus EPS regulation
Type IV pili function upstream of the Dif chemotaxis pathway in Myxococcus xanthus EPS regulation
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DOI：
10.1111/j.1365-2958.2006.05230.x
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发表时间：
2006-07-01
影响因子：
3.6
通讯作者：
Yang, Zhaomin
中科院分区：
文献类型：
--
作者：
Black, Wesley P.;Xu, Qian;Yang, Zhaomin
发育中的细菌黄粘球菌在形成多细胞子实体的过程中利用滑动运动聚集。黄原草滑翔运动的社会性(S)成分至少需要两种细胞外表面结构，IV型菌毛（Tfp）和原纤维多糖或外多糖（EPS）。Tfp的收缩被认为是为S的运动提供动力，而来自邻近细胞的EPS被认为是Tfp收缩的锚点和触发点。黄原草中EPS的产生部分受Dif化学感觉通路的调控；然而，Dif通路在EPS调控中的输入信号仍未被揭示。利用定量和定性分析相结合的遗传方法，我们在这里证明了Tfp在调节EPS产生的Dif蛋白上游起作用。利用不同类型的Tfp突变体验证了生产EPS所需的Tfp。双突变体和三突变体的构建和检测表明，dif的突变与pil的突变具有上位性。此外，各种Tfp和dif突变体之间的细胞外互补表明，Tfp可能不是信号，而是负责介导信号输入到dif通路的传感器或传感器的一部分。我们认为S的运动涉及一个调控回路，其中EPS触发Tfp收缩，Tfp向Dif通路提供邻近信号来调节EPS的产生。
The developmental bacterium Myxococcus xanthus utilizes gliding motility to aggregate during the formation of multicellular fruiting bodies. The social (S) component of M. xanthus gliding motility requires at least two extracellular surface structures, type IV pili (Tfp) and the fibril polysaccharide or exopolysaccharide (EPS). Retraction of Tfp is proposed to power S motility and EPS from neighbouring cells is suggested to provide an anchor and trigger for Tfp retraction. The production of EPS in M. xanthus is regulated in part by the Dif chemosensory pathway; however, the input signal for the Dif pathway in EPS regulation remains to be uncovered. Using a genetic approach combined with quantitative and qualitative analysis, we demonstrate here that Tfp function upstream of the Dif proteins in regulating EPS production. The requirement of Tfp for the production of EPS was verified using various classes of Tfp mutants. Construction and examination of double and triple mutants indicated that mutations in dif are epistatic to those in pil. Furthermore, extracellular complementation between various Tfp and dif mutants suggests that Tfp, instead of being signals, may constitute the sensor or part of the sensor responsible for mediating signal input into the Dif pathway. We propose that S motility involves a regulatory loop in which EPS triggers Tfp retraction and Tfp provide proximity signals to the Dif pathway to modulate EPS production.