A bacterial E3 ubiquitin ligase targets a host protein kinase to disrupt plant immunity
A bacterial E3 ubiquitin ligase targets a host protein kinase to disrupt plant immunity
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DOI：
10.1038/nature05966
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发表时间：
2007-07-19
期刊：
影响因子：
64.8
通讯作者：
Martin, Gregory B.
中科院分区：
文献类型：
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作者：
Rosebrock, Tracy R.;Zeng, Lirong;Martin, Gregory B.
植物和动物的许多细菌病原体使用III型分泌系统将多种与毒力相关的“效应”蛋白递送到宿主细胞中（1）。这些效应物的作用机制大多是未知的;然而，它们通常通过抑制宿主免疫来促进疾病（2）。一种III型效应子AvrPtoB由植物病原体假单胞菌致病变种表达。番茄，有一个羧基末端结构域，是E3泛素连接酶（3）。该结构域的缺失允许AvrPtoB（AvrPtoB（1-387））的氨基末端区域被某些番茄品种检测到，导致免疫相关的程序性细胞死亡（4）。在这里，我们表明宿主激酶Fen与AvrPtoB（1-387）物理相互作用，并负责激活植物免疫反应。AvrPtoB E3连接酶特异性泛素化Fen并以蛋白酶体依赖性方式促进其降解。这种降解导致Fen表达番茄品系的疾病易感性。发现番茄的各种野生物种对AvrPtoB（1-387）而不是全长AvrPtoB表现出免疫应答。因此，通过获得E3连接酶结构域，AvrPtoB阻碍了高度保守的宿主抗性机制。
Many bacterial pathogens of plants and animals use a type III secretion system to deliver diverse virulence-associated 'effector' proteins into the host cell(1). The mechanisms by which these effectors act are mostly unknown; however, they often promote disease by suppressing host immunity(2). One type III effector, AvrPtoB, expressed by the plant pathogen Pseudomonas syringae pv. tomato, has a carboxy-terminal domain that is an E3 ubiquitin ligase(3). Deletion of this domain allows an amino-terminal region of AvrPtoB (AvrPtoB(1-387)) to be detected by certain tomato varieties leading to immunity-associated programmed cell death(4). Here we show that a host kinase, Fen, physically interacts with AvrPtoB(1-387) and is responsible for activating the plant immune response. The AvrPtoB E3 ligase specifically ubiquitinates Fen and promotes its degradation in a proteasome-dependent manner. This degradation leads to disease susceptibility in Fen-expressing tomato lines. Various wild species of tomato were found to exhibit immunity in response to AvrPtoB(1-387) and not to full-length AvrPtoB. Thus, by acquiring an E3 ligase domain, AvrPtoB has thwarted a highly conserved host resistance mechanism.