A single region of the Pseudomonas putida genome, designated the flagellar cluster, includes 59 genes potentially involved in the biogenesis and function of the flagellar system. Here, we combine bioinformatics and in vivo gene expression analyses to clarify the transcriptional organization and regulation of the flagellar genes in the cluster. We have identified 11 flagellar operons and characterized 22 primary and internal promoter regions. Our results indicate that synthesis of the flagellar apparatus and core chemotaxis machinery is regulated by a three-tier cascade in which fleQ is a Class I gene, standing at the top of the transcriptional hierarchy. FleQ- and σ⁵⁴-dependent Class II genes encode most components of the flagellar structure, part of the chemotaxis machinery and multiple regulatory elements, including the flagellar σ factor FliA. FliA activation of Class III genes enables synthesis of the filament, one stator complex and completion of the chemotaxis apparatus. Accessory regulatory proteins and an intricate operon architecture add complexity to the regulation by providing feedback and feed-forward loops to the main circuit. Because of the high conservation of the gene arrangement and promoter motifs, we believe that the regulatory circuit presented here may also apply to other environmental pseudomonads.

中文翻译：

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恶臭假单胞菌鞭毛系统的转录组织和调控

恶臭假单胞菌基因组的单个区域，称为鞭毛簇，包括 59 个可能参与鞭毛系统生物发生和功能的基因。在这里，我们结合生物信息学和体内基因表达分析来阐明簇中鞭毛基因的转录组织和调控。我们已经确定了 11 个鞭毛操纵子并表征了 22 个初级和内部启动子区域。我们的研究结果表明，鞭毛装置和核心趋化机制的合成受三层级联的调节，其中fleQ是 I 类基因，位于转录层次结构的顶部。FleQ- 和 σ ⁵⁴依赖的 II 类基因编码鞭毛结构的大部分成分、趋化机制的一部分和多种调节元件，包括鞭毛 σ 因子 FliA。III 类基因的 FliA 激活能够合成细丝、一个定子复合体并完成趋化装置。辅助调节蛋白和复杂的操纵子结构通过向主电路提供反馈和前馈回路增加了调节的复杂性。由于基因排列和启动子基序的高度保守性，我们相信这里提出的调控电路也可能适用于其他环境假单胞菌。