A bacterial effector protein modulates host cell-to-cell communication

项目摘要 细胞间的通讯对植物的生长发育和胁迫适应至关重要 多细胞生物。植物细胞间信号分子的共体运输是由 膜衬里的通道被称为胞间连丝(PD)，而缝隙连接在 哺乳动物。虽然致病细菌感染多细胞生物体，但目前尚不清楚致病细菌是否 细菌利用宿主细胞间的通讯系统来促进细菌的繁殖。为了研究寄主- 病原菌的相互作用，我探索了拟南芥-丁香假单胞菌PV。番茄(PST)DC3000 病理系统。通常，几乎所有的植物病原菌都是胞外病原菌，包括Pst。 DC3000。植物通过其上的模式识别受体(PRRs)识别细菌病原体。 细胞膜(PM)和富含亮氨酸的核苷酸结合位点(NBS-LRR)型受体 细胞，导致防御激活。为克服植物防御，PST DC3000注入36个毒力 效应蛋白进入宿主细胞，发挥其致病活性。使用活细胞成像技术，我发现 PST DC3000效应蛋白HopO1-1是一种活性的ADP-核糖基转移酶，靶向于帕金森病 拟南芥。HopO1-1在拟南芥中的异位表达导致PD依赖增加 植物细胞间的分子通量。HopO1-1与拟南芥PD定位相关 蛋白质(PDLP5和PDLP7)，其中PDLP5的表达是由紫丁香菌感染和 参与植物的先天免疫。据我所知，HopO1-1是第一个被鉴定的细菌效应器 作为帕金森病靶标蛋白。这一发现增加了细菌病原体传递的令人兴奋的可能性 如HopO1-1等效应物，可能通过ADP-核糖基化PDLP5/7来调节宿主PD功能，从而 促进细菌的传播和繁殖。这项拟议工作的指导阶段将是 在杨合博士的指导下在密歇根州立大学进行。在这一阶段，我 计划(I)表征HopO1-1在调节宿主PD中的作用模式，(Ii)展示 依赖钯的细菌效应物从感染细胞到邻近细胞的运输，以及(Iii) 建立研究初始感染部位宿主-微生物动态相互作用的系统。何博士 将提供微生物学和植物-微生物相互作用方面的具体培训，以及指导 成为一名独立研究人员。在独立阶段，我计划研究(I)HopO1-1的作用 (Ii)HopO1-1在调控植物愈伤组织动态平衡中的作用 植物信号分子的运动，以及(Iii)HopO1-1在创造细菌中的功能作用 感染区在宿主组织中建立最初的定植。拟议中的项目有可能在 开辟细菌发病机制的新研究课题，建立新的实验方案 在宿主-细菌相互作用中细胞自主与非细胞自主效应的研究中。

Project Summary Cell-to-cell communication is crucial for growth and development as well as stress adaption in multicellular organisms. Symplastic transport of signaling molecules between plant cells is mediated by membrane-lined channels termed plasmodesmata (PD), whereas gap junctions play similar roles in mammals. Although pathogenic bacteria infect multicellular organisms, it is unclear whether pathogenic bacteria exploit host cell-to-cell communication system to promote bacterial multiplication. To study host- pathogen interactions, I explore Arabidopsis-Pseudomonas syringae pv. tomato (Pst) DC3000 pathosystem. Typically, almost all phytopathogenic bacteria are extracellular pathogen, including Pst DC3000. Bacterial pathogens are recognized by plants via pattern recognition receptors (PRRs) on the plasma membrane (PM) and nucleotide-binding site-leucine-rich repeat (NBS-LRR)-type receptors inside the cell, resulting in defense activation. To overcome plant defense, Pst DC3000 injects 36 virulence effector proteins into host cells to exert their pathogenic activities. Using live cell imaging, I discovered that Pst DC3000 effector protein HopO1-1, an active ADP-ribosyltransferase, is targeted to the PD in Arabidopsis. Ectopic expression of HopO1-1 in Arabidopsis leads to an increase in PD-dependent molecular flux between plant cells. HopO1-1 is physically associated with Arabidopsis PD-located proteins (PDLP5 and PDLP7), in which expression of PDLP5 is upregulated by P. syringae infection and involved in plant innate immunity. To my knowledge, HopO1-1 is the first bacterial effector to be identified as a PD-targeted protein. The finding raises the exciting possibility that bacterial pathogens deliver effectors such as HopO1-1 to modulate host PD function, presumably by ADP-ribosylating PDLP5/7, to facilitate bacterial spread and multiplication. The mentored phase of this proposed work will be conducted at Michigan State University under the guidance of Dr. Sheng Yang He. During this phase, I plan to (i) characterize the mode of action of HopO1-1 in modulating the host PD, (ii) demonstrate the PD-dependent trafficking of bacterial effectors from the infected cells to the neighboring cells, and (iii) establish systems in studying the dynamic host-microbe interactions at the initial infection sites. Dr. He will provide specific training in microbiology and plant-microbe interactions as well as guidance toward becoming an independent researcher. In the independent phase, I plan to study (i) the effect of HopO1-1 in regulating PD aperture by controlling plant callose homeostasis, (ii) the effect of HopO1-1 in the movement of plant signaling molecules, and (iii) the functional role of HopO1-1 on creating bacterial infection zones to establish the initial colonization in host tissues. The proposed project has potential in carving out a new research topic in bacterial pathogenesis and establishing new experimental protocols in the study of cell-autonomous vs. non-cell-autonomous effects in host-bacterial interactions.