Gene expression is adjusted according to cellular needs through a combination of mechanisms acting at different layers of the flow of genetic information. At the posttranscriptional level, RNA-binding proteins are key factors controlling the fate of nascent and mature mRNAs. Among them, the members of the CsrA family are small dimeric proteins with heterogeneous distribution across the bacterial tree of life, that act as global regulators of gene expression because they recognize characteristic sequence/structural motifs (short hairpins with GGA triplets in the loop) present in hundreds of mRNAs. The regulatory output of CsrA binding to mRNAs is counteracted in most cases by molecular mimic, non-protein coding RNAs that titrate the CsrA dimers away from the target mRNAs. In γ-proteobacteria, the regulatory modules composed by CsrA homologs and the corresponding antagonistic sRNAs, are mastered by two-component systems of the GacS-GacA type, which control the transcription and the abundance of the sRNAs, thus constituting the rather linear cascade Gac-Rsm that responds to environmental or cellular signals to adjust and coordinate the expression of a set of target genes posttranscriptionally. Within the γ-proteobacteria, the genus Pseudomonas has been shown to contain species with different number of active CsrA (RsmA) homologs and of molecular mimic sRNAs. Here, with the help of the increasing availability of genomic data we provide a comprehensive state-of-the-art picture of the remarkable multiplicity of CsrA lineages, including novel yet uncharacterized paralogues, and discuss evolutionary aspects of the CsrA subfamilies of the genus Pseudomonas, and implications of the striking presence of csrA alleles in natural mobile genetic elements (phages and plasmids).

根据细胞需求，通过作用于遗传信息流不同层面的机制的组合来调节基因表达。在转录后水平，RNA结合蛋白是控制新生和成熟mRNA命运的关键因素。其中，CsrA家族的成员是小的二聚体蛋白，在细菌的整个生命树中分布不均，它们充当基因表达的全局调节剂，因为它们识别存在的特征序列/结构基序（短发夹，带有GGA三联体）在数百种mRNA中 在大多数情况下，分子模拟，非蛋白质编码的RNA使CsrA二聚体远离目标mRNA滴定，抵消了与mRNA结合的CsrA的调节输出。在γ-变形杆菌中 由CsrA同源物和相应的拮抗sRNA组成的调节模块由GacS-GacA类型的两组分系统控制，该系统控制sRNA的转录和丰度，从而构成了响应于环境或细胞信号来调节和协调转录后一组靶基因的表达。在γ-变形杆菌内，属假单胞菌已显示含有不同数量的活性CsrA（RsmA）同源物和分子模拟sRNA的物种。在这里，借助基因组数据的日益增加，我们提供了CsrA谱系显着多样性的全面的最新图片，包括新颖但未表征的旁系同源物，并讨论了该属CsrA子家族的进化方面假单胞菌以及引人注目的存在 csrA 天然移动遗传元件（噬菌体和质粒）中的等位基因。