鞭毛是多蛋白复合物,其组装和定位需要复杂的时空控制。鞭毛组装被认为受几个转录层的控制,这些转录层通过各种主调节器介导。在这里,我们通过调节剂 FlrA、RpoN (σ 54 ) 和 FliA (σ 28 ) 在Shewanella putrefaciens中重新审视了极性鞭毛γ-变形杆菌中鞭毛基因的调节转录本和蛋白质水平的 CN-32。我们发现在没有主要监管机构的情况下存在许多监管和结构蛋白,这表明鞭毛组装和运动激活的启动仅依赖于形成 MS 所需的少数结构关键组件的丰度控制- 和 C 环和鞭毛 III 型分泌系统。我们确定了独立于 FlrA 的启动子驱动鞭毛数量和定位的调节器 FlhF 和 FlhG 的表达。来自这些启动子的基因表达水平的降低导致了鞭毛过度形成的出现。这一发现表明需要基础表达来调整Shewanella中的鞭毛计数器. 这为鞭毛合成和组装的调节增加了一个更深的层次。
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FlrA-independent production of flagellar proteins is required for proper flagellation in Shewanella putrefaciens
Flagella are multiprotein complexes whose assembly and positioning require complex spatiotemporal control. Flagellar assembly is thought to be controlled by several transcriptional tiers, which are mediated through various master regulators. Here, we revisited the regulation of flagellar genes in polarly flagellated gammaproteobacteria by the regulators FlrA, RpoN (σ54) and FliA (σ28) in Shewanella putrefaciens CN-32 at the transcript and protein level. We found that a number of regulatory and structural proteins were present in the absence of the main regulators, suggesting that initiation of flagella assembly and motor activation relies on the abundance control of only a few structural key components that are required for the formation of the MS- and C-ring and the flagellar type III secretion system. We identified FlrA-independent promoters driving expression of the regulators of flagellar number and positioning, FlhF and FlhG. Reduction of the gene expression levels from these promoters resulted in the emergence of hyperflagellation. This finding indicates that basal expression is required to adjust the flagellar counter in Shewanella. This is adding a deeper layer to the regulation of flagellar synthesis and assembly.