Functional characterization of bacterial type III effectors in plant cells

植物细胞中细菌 III 型效应子的功能表征

• 批准号: 250452489
• 负责人: Professor Dr. Frederik Börnke
• 金额: --
• 依托单位: Leibniz-Institut für Gemüse- und Zierpflanzenbau (IGZ) e.V.
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/250452489?language=en
• 关键词: Functional; characterization; bacterial; type; III

Pathogenicity of many Gram-negative pathogenic bacteria depends on a type III secretion system, which translocates bacterial effector proteins into the host cell. These type III effector proteins (T3Es) have evolved to function in a eukaryotic context in order to promote colonization of the host. The molecular mechanisms by which these T3Es alter host cellular processes are far from being understood. In our preliminary work we were able to show that HopZ1a, a T3E from Pseudomonas syringae, interacts with a previously uncharacterized remorin protein inside plant cells. Further interaction studies indicate that the remorin protein binds to and is specifically phosphorylated by the immune kinase PBS1 and also interacts with the E3 ligase SINA4. Overexpression of the remorin leads to increased basal PTI marker gene expression and induced ROS production after a flg22 stimulus. Our findings led to the hypothesis that the remorin might act in a complex together with PBS1 during PTI and hence is targeted by HopZ1a to manipulate immune signaling. Within the proposed project we will investigate the biochemical and molecular mechanism by which HopZ1a interferes with remorin function and how this leads to suppression of immunity. In addition, we could show that the T3E XopS form Xanthomonas campestris interacts inside the plant cell nucleus with a protein pair consisting of the transcription factor WRKY40 and an E3-ubiquitin ligase. The E3 ligase interacts with WRKY40 in vitro and in planta and ubiquitinates the transcription factor in vitro. Accordingly, transient expression in leaves of Nicotiana benthamiana suggests that WRKY40 undergoes rapid proteasomal protein turnover. However, WRKY40 protein strongly accumulates upon co-expression with XopS, indicating that XopS interferes with proteasomal turnover of WRKY40 and thus could interfere with defense gene induction that requires degradation of this negative regulator of plant defense. The second aim of the project is to unravel how XopS alters WRKY40 function and how this impacts on induced defense responses in host plants.

许多革兰氏阴性病原菌的致病性依赖于III型分泌系统，其将细菌效应蛋白易位到宿主细胞中。这些III型效应蛋白（T3 E）已经进化到在真核背景下发挥作用，以促进宿主的定殖。这些T3 E改变宿主细胞过程的分子机制远未被理解。在我们的初步工作中，我们能够证明HopZ 1a，一种来自假单胞菌的T3 E，与植物细胞内以前未表征的蛋白质相互作用。进一步的相互作用研究表明，该蛋白质结合并特异性磷酸化的免疫激酶PBS 1，也与E3连接酶SINA 4相互作用。过表达的flg 22刺激后，过表达的flg 22导致增加的基础PTI标记基因的表达和诱导的ROS的产生。我们的研究结果导致了这样的假设，即在PTI期间，Bisplin可能与PBS 1一起作用于复合物中，因此被HopZ 1a靶向以操纵免疫信号。在拟议的项目中，我们将研究HopZ 1a干扰免疫球蛋白功能的生化和分子机制，以及这如何导致免疫抑制。此外，我们可以表明，Xanthomonascampestris的T3 E XopS与转录因子WRKY 40和E3-泛素连接酶组成的蛋白质对在植物细胞核内相互作用。E3连接酶在体外和植物中与WRKY 40相互作用，并在体外泛素化转录因子。因此，在本氏烟草叶中的瞬时表达表明WRKY 40经历快速的蛋白酶体蛋白周转。然而，WRKY 40蛋白在与XopS共表达时强烈积累，表明XopS干扰WRKY 40的蛋白酶体周转，从而可能干扰需要降解这种植物防御负调节因子的防御基因诱导。该项目的第二个目的是揭示XopS如何改变WRKY 40的功能，以及这如何影响宿主植物的诱导防御反应。