State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China.
National Engineering Laboratory of Grain Storage and Logistics, Academy of National Food and Strategic Reserves Administration, No. 11 Baiwanzhuang Street, Xicheng District, Beijing 100037, China.
Int J Mol Sci. 2021 Nov 24;22(23):12692. doi: 10.3390/ijms222312692.
σ factor (RpoN), a type of transcriptional regulatory factor, is widely found in pathogenic bacteria. It binds to core RNA polymerase (RNAP) and regulates the transcription of many functional genes in an enhancer-binding protein (EBP)-dependent manner. σ has two conserved functional domains: the activator-interacting domain located at the N-terminal and the DNA-binding domain located at the C-terminal. RpoN directly binds to the highly conserved sequence, GGNGC, at the -24/-12 position relative to the transcription start site of target genes. In general, bacteria contain one or two RpoNs but multiple EBPs. A single RpoN can bind to different EBPs in order to regulate various biological functions. Thus, the overlapping and unique regulatory pathways of two RpoNs and multiple EBP-dependent regulatory pathways form a complex regulatory network in bacteria. However, the regulatory role of RpoN and EBPs is still poorly understood in phytopathogenic bacteria, which cause economically important crop diseases and pose a serious threat to world food security. In this review, we summarize the current knowledge on the regulatory function of RpoN, including swimming motility, flagella synthesis, bacterial growth, type IV pilus (T4Ps), twitching motility, type III secretion system (T3SS), and virulence-associated phenotypes in phytopathogenic bacteria. These findings and knowledge prove the key regulatory role of RpoN in bacterial growth and pathogenesis, as well as lay the groundwork for further elucidation of the complex regulatory network of RpoN in bacteria.
σ 因子（RpoN）是一种转录调控因子，广泛存在于致病菌中。它与核心 RNA 聚合酶（RNAP）结合，以增强子结合蛋白（EBP）依赖性的方式调节许多功能基因的转录。σ 具有两个保守的功能结构域：位于 N 端的激活剂相互作用结构域和位于 C 端的 DNA 结合结构域。RpoN 直接结合到靶基因转录起始位点上游-24/-12 位置高度保守的 GGNGC 序列上。通常，细菌含有一个或两个 RpoN，但有多个 EBP。单个 RpoN 可以与不同的 EBP 结合，以调节各种生物学功能。因此，两个 RpoN 和多个 EBP 依赖性调控途径的重叠和独特调控途径形成了细菌中复杂的调控网络。然而，在引起重要经济作物病害并对世界粮食安全构成严重威胁的植物病原菌中，RpoN 和 EBP 的调控作用仍知之甚少。在这篇综述中，我们总结了 RpoN 在游泳运动、鞭毛合成、细菌生长、IV 型菌毛（T4Ps）、蠕动运动、III 型分泌系统（T3SS）和与毒力相关的表型等方面的调控功能的最新知识。这些发现和知识证明了 RpoN 在细菌生长和发病机制中的关键调控作用，并为进一步阐明 RpoN 在细菌中复杂的调控网络奠定了基础。
