Exploring the impact of Xanthomonas euvesicatoria effector XopL on ABA signaling and host cell metabolism.

黄单胞菌是革兰氏阴性植物病原体的一个属，在全世界数百种重要的经济作物中引起疾病。黄单胞菌是半生物营养病原体，其生命周期的大部分时间都生活在活的植物组织中（生物营养阶段），但最终在感染的后期阶段（坏死性阶段）导致细胞死亡。生物营养生长阶段需要不断颠覆植物免疫系统，同时将植物细胞外质体转化为可居住的环境。为了应对这些挑战，黄单胞菌利用iii型分泌系统（T3SS）将细菌衍生的iii型分泌效应蛋白（T3Es）直接注入宿主细胞质。T3Es对病原体的毒力至关重要，一般认为，一旦进入，T3Es就会操纵植物细胞过程以支持外质体中的生命。对效应靶点的深入研究已经揭示了许多容易受到病原体攻击的植物过程，但这些效应功能究竟如何转化为黄单胞菌实际所在的外质体的变化，通常还没有得到充分的研究。为了进一步了解黄单胞菌的毒力，我们需要将细胞内的T3E功能与细胞内细菌的结果联系起来。辣椒和番茄细菌性斑疹病的病原菌evesicatoria （Xe）菌株85-10分泌36种效应蛋白，其中许多被称为黄单胞菌外蛋白（Xops）。其中一种蛋白质，XopL，在植物中显示E3连接酶功能，它劫持植物泛素化级联来修饰植物底物蛋白。对XopL的初步研究表明，它可能通过靶向已知的ABA信号成分ARIA（与ABF相互作用的ARM REPEAT蛋白）降解来操纵宿主细胞代谢。ARIA调节了影响外质体中病原体生长成功的初级和次级代谢物产生的重要基因的表达。该项目的目标是利用XopL-ARIA相互作用作为案例研究，以确定细胞内ABA信号级联的操纵是否与外质体的变化有关。

Xanthomonads are a genus of Gram-negative phytopathogens that cause disease in hundreds of economically important crop species worldwide. Xanthomonads are hemibiotrophic pathogens which spend a disproportionate amount of their life cycle living in/feeding off living plant tissue (biotrophic phase), but ultimately cause cell death during later stages of the infection (necrotrophic phase). Biotrophic growth phases require constant subversion of the plant immune system, and simultaneous conversion of the plant cell apoplast into a habitable environment. To address these challenges Xanthomonads utilize the type-III secretion system (T3SS) to inject bacterial-derived type III-secreted effector proteins (T3Es) directly into the host cytosol. T3Es are essential to pathogen virulence and it is generally understood that once inside, T3Es manipulate plant cell processes to support life in the apoplast. Intensive research into effector targets have revealed many of the plant processes that are vulnerable to pathogen attack, but exactly how these effector functions translate to changes in the apoplast where Xanthomonas actually resides are generally understudied. Going forward an understanding of Xanthomonas virulence requires that we link T3E function inside the cell to outcomes for the bacteria in the intracellular space.X. euvesicatoria (Xe) strain 85-10, the causal agent of bacterial spot disease on pepper and tomato, secretes 36 effector proteins, many of which are termed Xanthomonas outer proteins (Xops). One such protein, XopL, displays E3 ligase function in plants, where it hijacks the plant ubiquitylation cascade to modify plant substrate proteins. Preliminary work on XopL suggests that it might manipulate host cell metabolism by targeting a known ABA signaling component, ARIA (ARM REPEAT PROTEIN INTERACTING WITH ABF), for degradation. ARIA regulates the expression of genes important for the production of primary and secondary metabolites known to influence the success of pathogen growth in the apoplast. The goal of the proposed project is to utilize the XopL-ARIA interaction as a case study to determine whether the manipulation of the ABA signal cascade inside the cell can be linked to changes in the apoplast.