Antagonistic regulation of motility and transcriptome expression by RpoN and RpoS in Escherichia coliJournal Articles
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SummaryBacteria generally possess multiple σ factors that, based on structural and functional similarity, divide into two families: σ70 and σN. Many studies have revealed σ factor competition within the σ70 family, while the competition between σN and σ70 families has yet to be fully explored. Here we report a global antagonistic effect on gene expression between two alternative σ factors, σN (RpoN) and a σ70 family protein σS (RpoS). Mutations in rpoS and rpoN were found to inversely affect a number of cellular traits, such as the expression of flagellar genes, σN‐controlled growth on poor nitrogen sources, and σS‐directed expression of acid phosphatase AppA. Transcriptome analysis reveals that about 60% of genes in the RpoN regulon are under reciprocal RpoS control. Furthermore, loss of RpoN led to increased levels of RpoS, while RpoN levels were unaffected by the rpoS mutation. Expression of the flagellar σF factor (FliA), another σ70 family protein, is controlled positively by RpoN but negatively by RpoS. This positive control by RpoN is likely mediated through the flagellar regulator FlhDC, whose expression is RpoN‐dependent. These findings unveil a complex regulatory interaction among σN, σS and σF, which modulates motility, nitrogen utilization, stress response and many other cellular functions.
