Small non‐coding RNAs (sRNAs) control bacterial gene expression involved in a wide range of important cellular processes. In the highly social bacterium Myxococcus xanthus, the sRNA Pxr prevents multicellular fruiting‐body development when nutrients are abundant. Pxr was discovered from the evolution of a developmentally defective strain (OC) into a developmentally proficient strain (PX). In OC, Pxr is constitutively expressed and blocks development even during starvation. In PX, one mutation deactivates Pxr allowing development to proceed. We screened for transposon mutants that suppress the OC defect and thus potentially reveal new Pxr‐pathway components. Insertions significantly restoring development were found in four genes—rnd, rnhA, stkA and Mxan_5793—not previously associated with an sRNA activity. Phylogenetic analysis suggests that the Pxr pathway was constructed within the Cystobacterineae suborder both by co‐option of genes predating the Myxococcales order and incorporation of a novel gene (Mxan_5793). Further, the sequence similarity of rnd, rnhA and stkA homologs relative to M. xanthus alleles was found to decrease greatly among species beyond the Cystobacterineae suborder compared to the housekeeping genes examined. Finally, ecological context differentially affected the developmental phenotypes of distinct mutants, with implications for the evolution of development in variable environments.

中文翻译：

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调节粘细菌发育的sRNA途径基因表现出进化枝特异性进化。

小型非编码RNA（sRNA）控制涉及许多重要细胞过程的细菌基因表达。sRNA Pxr在高度社会化的细菌黄霉（Myxococcus xanthus）中，当营养丰富时阻止多细胞子实体的发育。Pxr是从发育缺陷菌株（OC）向发育熟练菌株（PX）的进化中发现的。在OC中，Pxr会组成型表达，甚至在饥饿期间也会阻止发育。在PX中，一个突变使Pxr失活，从而使发育得以进行。我们筛选了可抑制OC缺陷并因此可能揭示新的Pxr途径成分的转座子突变体。在四个基因（rnd，rnhA，stkA）中发现了显着恢复发育的插入和Mxan_5793-先前与sRNA活性无关。系统发育分析表明，Pxr途径是通过在粘菌球菌顺序之前选择基因并掺入新基因（Mxan_5793）来在胞杆菌属亚顺序内构建的。此外，在序列相似性RND，rnhA和stkA同系物相对于黄色粘球菌的等位基因被发现超出Cystobacterineae亚目物种相比于持家基因检查中大大降低。最后，生态环境对不同突变体的发育表型有不同的影响，对可变环境中的发育演化具有影响。