AvrBsT acetylates Arabidopsis ACIP1, a protein that associates with microtubules and is required for immunity.
AvrBsT acetylates Arabidopsis ACIP1, a protein that associates with microtubules and is required for immunity.
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DOI：
10.1371/journal.ppat.1003952
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发表时间：
2014-02
期刊：
影响因子：
6.7
通讯作者：
Mudgett MB
中科院分区：
文献类型：
--
作者：
Cheong MS;Kirik A;Kim JG;Frame K;Kirik V;Mudgett MB
植物和动物的细菌病原体共有一组同源的毒力因子，称为YopJ效应子家族，其在感染期间通过III型分泌（T3 S）系统易位到宿主细胞中。最近的工作表明，这些效应器中的一些编码乙酰转移酶，抑制宿主免疫。已知YopJ样蛋白AvrBsT在拟南芥Pi-0植物中激活效应子触发的免疫（ETI）;然而，其酶活性和宿主靶标的性质仍然难以捉摸。在这里，我们报告AvrBsT具有乙酰转移酶活性和乙酰化ACIP 1（乙酰化相互作用蛋白1），一个未知的蛋白质从拟南芥。遗传研究表明，拟南芥ACIP家族成员都需要病原体相关分子模式（PAMP）触发的免疫和AvrBsT触发的ETI在假单胞菌致病变种番茄DC 3000（Pst DC 3000）感染。显微镜研究表明，ACIP 1与细胞皮质上的点相关，其中一些点与微管共定位。这些结构在感染过程中发生了巨大的变化。Pst DC 3000或Pst DC 3000 AvrRpt 2感染引发了许多小ACIP 1点和杆的形成。相比之下，Pst DC 3000 AvrBsT感染主要以乙酰转移酶依赖性方式触发大GFP-ACIP 1聚集体的形成。我们的数据表明，ACIP家族成员是抗菌免疫所需的防御机制的新组成部分。他们还表明，植物中AvrBsT依赖性乙酰化改变了ACIP 1的防御功能，这与ETI的激活有关。宿主抗病途径如何被激活以响应病原体仍然是宿主-病原体相互作用中的一个基本问题。在这项工作中，我们使用假单胞菌-拟南芥病理系统来研究AvrBsT效应子如何激活植物免疫信号。AvrBsT属于YopJ效应子家族，一组由植物和动物的细菌病原体共享的毒力蛋白。细菌将这些效应物注入植物或动物宿主细胞以促进致病。最近的生物化学研究表明，YopJ家族的几个成员编码乙酰转移酶，乙酰化宿主蛋白质以抑制免疫信号传导。免疫系统如何特异性地识别这个效应子家族和/或监测宿主乙酰化尚不清楚。在这项工作中，我们提供了生化证据，AvrBsT是一种乙酰转移酶。我们还报告了ACIP 1，拟南芥蛋白的未知功能，是一个AvrBsT基板的鉴定和表征。我们提供的证据表明，ACIP 1是植物免疫所需的，它与感染过程中微管的变化。此外，我们的工作表明，AvrBsT乙酰转移酶在植物中导致ACIP 1本地化的巨大变化，这与强烈的防御反应的激活相一致。这项研究强调了ACIP 1与抗细菌免疫过程中微管网络之间的重要联系。
Bacterial pathogens of plant and animals share a homologous group of virulence factors, referred to as the YopJ effector family, which are translocated by the type III secretion (T3S) system into host cells during infection. Recent work indicates that some of these effectors encode acetyltransferases that suppress host immunity. The YopJ-like protein AvrBsT is known to activate effector-triggered immunity (ETI) in Arabidopsis thaliana Pi-0 plants; however, the nature of its enzymatic activity and host target(s) has remained elusive. Here we report that AvrBsT possesses acetyltransferase activity and acetylates ACIP1 (for ACETYLATED INTERACTING PROTEIN1), an unknown protein from Arabidopsis. Genetic studies revealed that Arabidopsis ACIP family members are required for both pathogen-associated molecular pattern (PAMP)-triggered immunity and AvrBsT-triggered ETI during Pseudomonas syringae pathovar tomato DC3000 (Pst DC3000) infection. Microscopy studies revealed that ACIP1 is associated with punctae on the cell cortex and some of these punctae co-localize with microtubules. These structures were dramatically altered during infection. Pst DC3000 or Pst DC3000 AvrRpt2 infection triggered the formation of numerous, small ACIP1 punctae and rods. By contrast, Pst DC3000 AvrBsT infection primarily triggered the formation of large GFP-ACIP1 aggregates, in an acetyltransferase-dependent manner. Our data reveal that members of the ACIP family are new components of the defense machinery required for anti-bacterial immunity. They also suggest that AvrBsT-dependent acetylation in planta alters ACIP1's defense function, which is linked to the activation of ETI. How host disease resistance pathways are activated in response to pathogens remains a fundamental question in host-pathogen interactions. In this work, we used the Pseudomonas-Arabidopsis pathosystem to study how the AvrBsT effector activates plant immune signaling. AvrBsT belongs to the YopJ effector family, a group of virulence proteins shared by bacterial pathogens of plants and animals. Bacteria inject these effectors into plant or animal host cells to promote pathogenesis. Recent biochemical studies show that several members of the YopJ family encode acetyltransferases that acetylate host proteins to suppress immune signaling. How the immune system specifically recognizes this family of effectors and/or monitors host acetylation is poorly understood. In this work, we provide biochemical evidence that AvrBsT is an acetyltransferase. We also report the identification and characterization of ACIP1, an Arabidopsis protein of unknown function that is an AvrBsT substrate. We provide evidence that ACIP1 is required for plant immunity and its association with microtubules changes during infection. Moreover, our work suggests that AvrBsT acetyltransferase in planta leads to dramatic changes in ACIP1 localization, which coincides with the activation of strong defense responses. This study highlights an important link between ACIP1 and the microtubule network during anti-bacterial immunity.
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