Deciphering the functions of type II and type IV secretion systems from the plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria

破译植物病原菌黄单胞菌的 II 型和 IV 型分泌系统的功能。

• 批准号: 194115428
• 负责人: Professorin Dr. Daniela Büttner
• 金额: --
• 依托单位: Abteilung Pflanzengenetik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2011
• 资助国家: 德国
• 起止时间: 2010-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/194115428?language=en
• 关键词: Deciphering; functions; type; II; IV

The Gram-negative plant-pathogenic bacterium Xanthomonas campestris pv. vesicatoria (Xcv) is the causal agent of bacterial spot disease on pepper and tomato plants and one of the model organisms to study secretion of bacterial virulence factors. Essential for pathogenicity of Xcv is the type III secretion system, which translocates bacterial effector proteins into eukaryotic cells. Furthermore, the efficient interaction of Xcv with its host plants depends on the Xps-type II secretion (T2S) system, which secretes degradative enzymes into the extracellular milieu. We previously showed that the T2S secretomes vary in different pathovars of X. campestris, which is in contrast to the previously anticipated conservation of bacterial T2S substrate specificities. The Xps-T2S system from Xcv secretes proteases, xylanases and a lipase, which contribute to bacterial virulence. In the absence of functional T2S systems, secretion of T2S substrates from Xcv was not completely abolished, suggesting that they are targeted to alternative transport routes. In agreement with this observation, we detected T2S substrates in outer membrane vesicles (OMVs) of Xcv. In the present project, we want to characterize the contribution of OMVs to the secretion of virulence factors from Xcv. Furthermore, we propose to investigate possible interactions between T2S substrates and components of the secretion apparatus and to identify protein regions, which are involved in substrate docking. In addition to the analysis of the T2S system and OMVs, we aim at the functional characterization of the two type IV secretion (T4S) systems of Xcv, which resemble the VirB/D4-T4S system from Agrobacterium tumefaciens and the Icm/Dot-T4S system from the animal-pathogenic bacterium Legionella pneumophila, respectively. Xcv is the only known plant-pathogenic bacterium, which contains an Icm/Dot-like T4S system. Our recent mutant studies revealed that both T4S systems contribute to the interaction of X. campestris pv. vesicatoria with susceptible pepper plants. Furthermore, bioinformatic approaches led to the identification of candidate T4S substrates, which are homologous to known T4S effectors and/or contain conserved C-terminal amino acid motifs, which presumably serve as secretion signals. In the present project, we will study secretion and translocation of candidate T4S substrates from Xcv and their potential contribution to bacterial virulence. Furthermore, given the recent report on the role of the VirB/D4-like T4S system from the related pathogen Xanthomonas axonopodis pv. citri in bacterial killing, we will investigate a possible role of T4S systems in the interaction of Xcv with other bacterial cells.

野油菜黄单胞菌（Xanthomonascampestris pv.）水泡孢菌（Xcv）是辣椒和番茄细菌性斑点病的病原菌，也是研究细菌毒力因子分泌的模式生物之一。Xcv致病性的关键是III型分泌系统，其将细菌效应蛋白易位到真核细胞中。此外，Xcv与其宿主植物的有效相互作用依赖于Xps-II型分泌（T2 S）系统，该系统将降解酶分泌到细胞外环境中。我们以前的研究表明，T2 S分泌体在X的不同致病型中是不同的。campestris，这与先前预期的细菌T2 S底物特异性的保守性相反。来自Xcv的Xps-T2 S系统分泌蛋白酶、木聚糖酶和脂肪酶，其有助于细菌毒力。在没有功能性T2 S系统的情况下，从Xcv分泌T2 S底物没有被完全消除，这表明它们被靶向替代运输途径。与此观察结果一致，我们检测到T2 S底物外膜囊泡（OMV）的XCV。在本项目中，我们希望表征OMV对Xcv毒力因子分泌的贡献。此外，我们建议调查T2 S基板和分泌装置的组件之间可能的相互作用，并确定蛋白质区域，这是参与基板对接。除了T2 S系统和OMV的分析，我们的目标是在功能特性的两个IV型分泌（T4 S）系统的Xcv，这类似于VirB/D4-T4 S系统从根癌农杆菌和Icm/Dot-T4 S系统从动物病原性细菌嗜肺军团菌，分别。Xcv是目前已知的唯一一种植物病原细菌，它含有一个类似Icm/Dot的T4 S系统。我们最近的突变体研究表明，这两个T4 S系统有助于X的相互作用。野油菜致病变种vesicatoria与敏感的辣椒植物。此外，生物信息学方法导致候选T4 S底物的鉴定，其与已知的T4 S效应物同源和/或含有保守的C-末端氨基酸基序，其推测用作分泌信号。在本项目中，我们将研究Xcv的候选T4 S底物的分泌和易位及其对细菌毒力的潜在贡献。此外，鉴于最近关于来自相关病原体Xanthomonaxonopodispv. citri在细菌杀伤中的作用，我们将研究T4 S系统在Xcv与其他细菌细胞相互作用中的可能作用。