Silencing of subfamily I of protein phosphatase 2A catalytic subunits results in activation of plant defense responses and localized cell death
Silencing of subfamily I of protein phosphatase 2A catalytic subunits results in activation of plant defense responses and localized cell death
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DOI：
10.1111/j.1365-313x.2004.02073.x
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发表时间：
2004-05-01
期刊：
影响因子：
7.2
通讯作者：
Martin, GB
中科院分区：
文献类型：
--
作者：
He, XH;Anderson, JC;Martin, GB
蛋白质磷酸化在植物防御反应中的重要性已经通过分离编码蛋白激酶的几个抗病基因得到证实。此外，有许多报道蛋白质磷酸化的变化伴随着植物对病原体的反应。相反，人们对蛋白质去磷酸化在调节植物防御中的作用知之甚少。我们报告的LePP2Ac1基因，它编码的异源三聚体蛋白磷酸酶2A（PP2Ac）的催化亚基的表达，是迅速诱导抗性番茄叶片接种后，与无毒菌株的假单胞菌pv。番茄通过对几种植物PP2Ac基因序列的分析，发现PP2Ac基因可分为两个亚家族，LePP2Ac 1属于亚家族I。本氏烟草中的病毒诱导的基因沉默（VIGS）用于抑制来自亚科I而不是来自亚科II的基因的表达。PP2Ac沉默的植物PP2A活性大大降低，组成型表达病程相关（PR）基因，并开发本地化的茎和叶细胞死亡。此外，植物对P. pueringae pv.的强毒株更具抗性。烟粉虱和表现出加速过敏反应（HR）的效应蛋白从P.tubingae和真菌病原体，Cladosporium fulvum。因此，PP2Ac亚家族I的催化亚基可能通过使蛋白质磷酸化级联反应脱敏而充当植物防御反应的负调节剂。
The central importance of protein phosphorylation in plant defense responses has been demonstrated by the isolation of several disease-resistance genes that encode protein kinases. In addition, there are many reports of changes in protein phosphorylation accompanying plant responses to pathogens. In contrast, little is known about the role of protein dephosphorylation in regulating plant defenses. We report that expression of the LePP2Ac1 gene, which encodes a catalytic subunit of the heterotrimeric protein phosphatase 2A (PP2Ac), is rapidly induced in resistant tomato leaves upon inoculation with an avirulent strain of Pseudomonas syringae pv. tomato. By analysis of PP2Ac gene sequences from several plant species, we found that PP2Ac genes cluster into two subfamilies, with LePP2Ac1 belonging to subfamily I. Virus-induced gene silencing (VIGS) in Nicotiana benthamiana was used to suppress expression of genes from subfamily I and not from subfamily II. The PP2Ac-silenced plants had greatly decreased PP2A activity, constitutively expressed pathogenesis-related (PR) genes, and developed localized cell death in stems and leaves. In addition, the plants were more resistant to a virulent strain of P. syringae pv. tabaci and showed an accelerated hypersensitive response (HR) to effector proteins from both P. syringae and the fungal pathogen, Cladosporium fulvum. Thus, catalytic subunits of PP2Ac subfamily I act as negative regulators of plant defense responses likely by de-sensitizing protein phosphorylation cascades.