The type III effector AvrXccB in Xanthomonas campestris pv. campestris targets putative methyltransferases and suppresses innate immunity in Arabidopsis
The type III effector AvrXccB in Xanthomonas campestris pv. campestris targets putative methyltransferases and suppresses innate immunity in Arabidopsis
复制标题
野油菜黄单胞菌 pv 中的 III 型效应子 AvrXccB。
DOI：
10.1111/mpp.12435
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发表时间：
2017-08-01
影响因子：
4.9
通讯作者：
Sun, Wenxian
中科院分区：
文献类型：
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作者：
Liu, Lijuan;Wang, Yanping;Sun, Wenxian
油菜黄单胞菌黑腐病是世界范围内芸苔属作物最重要的病害之一。III型效应子库在病原体的毒力和致病性中起重要作用。然而，关于Xcc中推定的III型效应子AvrXccB的毒力功能知之甚少。在这里，我们研究了AvrXccB的免疫抑制能力和可能的潜在机制。AvrXccB被证明以III型分泌系统依赖性方式分泌。用绿色荧光蛋白标记的AvrXccB在拟南芥中定位于质膜，并且推定的N-肉豆蔻酰化基序对其定位是必需的。化学诱导的AvrXccB表达抑制flg 22触发的愈伤组织沉积和氧化爆发，并促进Xcc和丁香假单胞菌pv.的植物生长。转基因拟南芥植物中的番茄。AvrXccB的推定催化三联体和质膜定位是其免疫抑制活性所必需的。此外，证明AvrXccB与拟南芥S-腺苷-L-甲硫氨酸依赖性甲基转移酶SAM-MT 1和SAM-MT 2相互作用。有趣的是，SAM-MT 1不仅自身相关，而且在体内与SAM-MT 2相关。SAM-MT 1和SAM-MT 2表达在微生物相关分子模式和细菌感染的刺激下被显著诱导。总的来说，这些发现表明AvrXccB靶向一个假定的甲基转移酶复合物，并抑制植物免疫。
Xanthomonas campestris pv. campestris (Xcc) causes black rot, one of the most important diseases of brassica crops worldwide. The type III effector inventory plays important roles in the virulence and pathogenicity of the pathogen. However, little is known about the virulence function(s) of the putative type III effector AvrXccB in Xcc. Here, we investigated the immune suppression ability of AvrXccB and the possible underlying mechanisms. AvrXccB was demonstrated to be secreted in a type III secretion system-dependent manner. AvrXccB tagged with green fluorescent protein is localized to the plasma membrane in Arabidopsis, and the putative N-myristoylation motif is essential for its localization. Chemical-induced expression of AvrXccB suppresses flg22-triggered callose deposition and the oxidative burst, and promotes the in planta growth of Xcc and Pseudomonas syringae pv. tomato in transgenic Arabidopsis plants. The putative catalytic triad and plasma membrane localization of AvrXccB are required for its immunosuppressive activity. Furthermore, it was demonstrated that AvrXccB interacts with the Arabidopsis S-adenosyl-l-methionine-dependent methyltransferases SAM-MT1 and SAM-MT2. Interestingly, SAM-MT1 is not only self-associated, but also associated with SAM-MT2 in vivo. SAM-MT1 and SAM-MT2 expression is significantly induced upon stimulation of microbe-associated molecular patterns and bacterial infection. Collectively, these findings indicate that AvrXccB targets a putative methyltransferase complex and suppresses plant immunity.