Molecular analysis of virulence and avirulence activities of the bacterial effector protein XopH and related proteins

细菌效应蛋白XopH及相关蛋白毒力和无毒活性的分子分析

• 批准号: 418274535
• 负责人: Professor Dr. Thomas Lahaye
• 金额: --
• 依托单位: Bereich Pflanzenernährung
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2019
• 资助国家: 德国
• 起止时间: 2018-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/418274535?language=en
• 关键词: Molecular; analysis; virulence; avirulence; activities

Microbial plant pathogens pose a permanent thread to global food security. Phytopathogenic microbes inject effector proteins into host cells via type III (T3) secretion systems, which are crucial to virulence since they manipulate plant cell physiology to the pathogen’s benefit. Some plant genotypes of otherwise susceptible host species contain resistance (R) proteins that recognize microbial effectors and in turn activate the plant’s defense system. Effectors that are recognized by the plant immune system have been coined as avirulence (Avr) proteins, since their presence converts virulent into avirulent strains. Molecular analysis of Avr-R interactions is imperative to elucidate the mechanistic basis of plant immunity, and provides the key for knowledge-based breeding of pest-resistant crops.We intend to study virulence and avirulence activities of XopH, an effector from the pepper and tomato pathogen Xanthomonas euvesicatoria (Xe). Recent studies revealed that XopH from Xe dephosphorylates phytate (myo-inositol-hexakisphosphate, InsP6), the major P storage compound in plants. XopH is the first T3-effector for which phytase activity has been demonstrated and is the first 1-phytase described in nature (dephosphorylation at position C1). Plants contain numerous inositol polyphosphates, and it remains to be clarified which of the XopH-dependent inositol polyphosphates promotes disease. XopH also triggers an immune reaction in pepper plants containing the cognate R gene Bs7. Preliminary work suggests that Bs7 detects the biological activity, rather than the structure of XopH.The following proposal has two distinct but interconnected aims. 1.) To study XopH and related microbial effectors at the biochemical, cellular and structural level. One major aim here is the identification of XopH-dependent inositol polyphosphates that promote disease and/or trigger plant defense. 2.) To isolate the pepper R gene Bs7 via positional cloning. Availability of a microbial T3 effector with inositol polyphosphate hydrolase activity and its matching host R protein provides the unique opportunity to elucidate for the first time how such an activity can translate into a plant immune reaction.The proposed research will be carried out in a collaborative effort of the Lahaye lab (Tübingen) and the Schaaf lab (Bonn). The Schaaf lab has comprehensive expertise in the biochemical analysis of myo-inositol-derived metabolites. The Lahaye lab has long-term experience in the functional analysis of microbial effectors and the positional-cloning of plant R genes from crop species. We expect that the complementary expertise of both labs will generate strong synergistic effects that will allow a deep mechanistic understanding of virulence and avirulence activities of XopH and related proteins that would not be possible without this concerted collaborative effort.

微生物植物病原体对全球粮食安全构成永久威胁。植物病原微生物通过III型（T3）分泌系统将效应蛋白注入宿主细胞，这对毒力至关重要，因为它们操纵植物细胞生理学以使病原体受益。一些易受感染的宿主物种的植物基因型含有抗性（R）蛋白，其识别微生物效应物并反过来激活植物的防御系统。被植物免疫系统识别的效应子被称为无毒（Avr）蛋白，因为它们的存在将毒性菌株转化为无毒菌株。Avr-R相互作用的分子研究是阐明植物免疫机制的基础，也是作物抗虫育种的关键。最近的研究表明，XopH可以使植物中主要的磷储存化合物肌醇六磷酸（myo-inositol-hexakisphosphate，InsP 6）脱磷酸。XopH是第一个T3效应子，已经证明其具有肌醇六磷酸酶活性，并且是自然界中描述的第一个1-肌醇六磷酸酶（在位置C1处脱磷酸化）。植物中含有大量的肌醇多磷酸，但仍有待澄清的是，哪种依赖于XOH的肌醇多磷酸会促进疾病。XopH还在含有同源R基因Bs 7的辣椒植物中引发免疫反应。初步研究表明，Bs 7检测的是XopH的生物活性，而不是XopH的结构。1.）的人。从生化、细胞和结构水平研究XopH及其相关的微生物效应因子。这里的一个主要目的是鉴定促进疾病和/或触发植物防御的XOH依赖性肌醇多磷酸。2.）的情况。通过定位克隆的方法分离辣椒抗病基因Bs 7。具有肌醇多磷酸水解酶活性的微生物T3效应子及其匹配的宿主R蛋白的可用性为首次阐明这种活性如何转化为植物免疫反应提供了独特的机会。拟议的研究将在Lahaye实验室（蒂宾根）和Schaaf实验室（波恩）的合作努力中进行。Schaaf实验室在肌醇衍生代谢物的生化分析方面拥有全面的专业知识。Lahaye实验室在微生物效应子的功能分析和作物物种植物R基因的定位克隆方面拥有长期经验。我们预计，两个实验室的互补专业知识将产生强大的协同效应，使人们能够深入了解XopH和相关蛋白的毒力和无毒力活动，如果没有这种协调一致的合作努力，这是不可能的。