College of Plant Protection, Nanjing Agricultural University, No.1 Weigang, Nanjing City, 210095, Jiangsu, China.
Key Laboratory of Integrated Management of Crop Diseases and Pests (Nanjing Agricultural University), Ministry of Education, Nanjing, China.
Appl Microbiol Biotechnol. 2018 Sep;102(17):7509-7519. doi: 10.1007/s00253-018-9196-x. Epub 2018 Jul 3.
Lysobacter enzymogenes is an agriculturally important Gram-negative bacterium that employs a multitude of antifungal mechanisms to inhibit and infect filamentous fungal pathogens, through secretion of antifungal antibiotic HSAF (heat-stable antifungal factor), formation of T4P (type IV pilus)-mediated twitching motility, and production of extracellular chitinase. Interestingly, all such key antifungal factors seem to be controlled by Clp, a master regulator in L. enzymogenes; however, the underlying mechanisms are poorly understood. Here, employing strain OH11 as a working model, we show that Clp plays a dual role in controlling OH11 twitching motility. It controls transcription of pilA, a major T4P structure pilin gene, via directly binding to its promoter region, as well as regulates the gene transcription of pilMONOPQ operon, whose products were essential for T4P assembly, by directly binding to a similar promoter sequence. We also truncated the Clp-binding region of the pilA promoter fragment down to 41 bp to identify the potential Clp-binding sequence. In addition, the Clp-recognized pilM promoter motif of the L. enzymogenes strains is similarly conserved as the pilA promoter, both with a conserved 5'-GTG and a conserved CAC-3', spaced by ten highly variable nucleotides. Thus, this study identified two direct and previously uncharacterized gene targets of Clp contributing to its regulation in the L. enzymogenes twitching motility. Overall, our findings further elucidate the molecular genetics of Clp-dependent twitching motility in Lysobacter.
解淀粉类芽胞杆菌是一种具有农业重要性的革兰氏阴性细菌，它通过分泌抗真菌抗生素 HSAF（热稳定抗真菌因子）、形成 T4P（类型 IV 菌毛）介导的蠕动运动以及产生细胞外几丁质酶等多种抗真菌机制来抑制和感染丝状真菌病原体。有趣的是，所有这些关键的抗真菌因子似乎都受到 Clp 的控制，Clp 是解淀粉类芽胞杆菌中的一个主要调控因子；然而，其潜在的机制还了解甚少。在这里，我们以菌株 OH11 作为工作模型，表明 Clp 在控制 OH11 蠕动运动中起双重作用。它通过直接结合其启动子区域来控制 T4P 主要结构菌毛基因 pilA 的转录，同时通过直接结合类似的启动子序列来调节 T4P 组装所必需的 pilMONOPQ 操纵子的基因转录。我们还将 pilA 启动子片段的 Clp 结合区截断到 41bp，以鉴定潜在的 Clp 结合序列。此外，解淀粉类芽胞杆菌菌株的 Clp 识别 pilM 启动子模体与 pilA 启动子相似，都具有保守的 5'-GTG 和保守的 CAC-3'，间隔十个高度可变的核苷酸。因此，这项研究确定了 Clp 直接调控解淀粉类芽胞杆菌蠕动运动的两个以前未被描述的基因靶标。总的来说，我们的发现进一步阐明了 Clp 依赖的解淀粉类芽胞杆菌蠕动运动的分子遗传学。
