Yuan Xiaochen, Yu Manda, Yang Ching-Hong
Department of Plant, Soil, and Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA.
Department of Biological Sciences, University of Wisconsin-Milwaukee, Milwaukee, WI 53211, USA.
Microorganisms. 2020 Dec 9;8(12):1956. doi: 10.3390/microorganisms8121956.
Many Gram-negative pathogenic bacteria rely on a functional type III secretion system (T3SS), which injects multiple effector proteins into eukaryotic host cells, for their pathogenicity. Genetic studies conducted in different host-microbe pathosystems often revealed a sophisticated regulatory mechanism of their T3SSs, suggesting that the expression of T3SS is tightly controlled and constantly monitored by bacteria in response to the ever-changing host environment. Therefore, it is critical to understand the regulation of T3SS in pathogenic bacteria for successful disease management. This review focuses on a model plant pathogen, , and summarizes the current knowledge of its T3SS regulation. We highlight the roles of several T3SS regulators that were recently discovered, including the transcriptional regulators: FlhDC, RpoS, and SlyA; the post-transcriptional regulators: PNPase, Hfq with its dependent sRNA ArcZ, and the RsmA/B system; and the bacterial second messenger cyclic-di-GMP (c-di-GMP). Homologs of these regulatory components have also been characterized in almost all major bacterial plant pathogens like , , spp., spp., and spp. The second half of this review shifts focus to an in-depth discussion of the innovation and development of T3SS inhibitors, small molecules that inhibit T3SSs, in the field of plant pathology. This includes T3SS inhibitors that are derived from plant phenolic compounds, plant coumarins, and salicylidene acylhydrazides. We also discuss their modes of action in bacteria and application for controlling plant diseases.
许多革兰氏阴性病原菌依靠功能性III型分泌系统（T3SS）来致病，该系统可将多种效应蛋白注入真核宿主细胞。在不同宿主 - 微生物病理系统中进行的遗传学研究常常揭示出其T3SS复杂的调控机制，这表明T3SS的表达受到细菌的严格控制，并会根据不断变化的宿主环境持续进行监测。因此，了解病原菌中T3SS的调控对于成功管理疾病至关重要。本综述聚焦于一种模式植物病原菌，并总结了目前关于其T3SS调控的知识。我们重点介绍了最近发现的几种T3SS调控因子的作用，包括转录调控因子：FlhDC、RpoS和SlyA；转录后调控因子：PNPase、与依赖的小RNA ArcZ相关的Hfq以及RsmA/B系统；以及细菌第二信使环二鸟苷酸（c-di-GMP）。这些调控成分的同源物在几乎所有主要的细菌植物病原菌中也都得到了表征，如、、 spp.、 spp.和 spp.。本综述的后半部分将重点转向深入讨论植物病理学领域中T3SS抑制剂（抑制T3SS的小分子）的创新与发展。这包括源自植物酚类化合物、植物香豆素和水杨醛酰肼的T3SS抑制剂。我们还讨论了它们在细菌中的作用方式以及在控制植物病害方面的应用。
