CSIR-Centre for Cellular and Molecular Biology (CSIR-CCMB), Hyderabad, 500007, India.
National Institute of Plant Genome Research, New Delhi, 110067, India.
Plant J. 2020 Oct;104(2):332-350. doi: 10.1111/tpj.14924. Epub 2020 Aug 19.
Xanthomonas oryzae pv. oryzae uses several type III secretion system (T3SS) secreted effectors, namely XopN, XopQ, XopX and XopZ, to suppress rice immune responses that are induced following treatment with cell wall degrading enzymes. Here we show that a T3SS secreted effector XopX interacts with two of the eight rice 14-3-3 proteins. Mutants of XopX that are defective in 14-3-3 binding are also defective in suppression of immune responses, suggesting that interaction with 14-3-3 proteins is required for suppression of host innate immunity. However, Agrobacterium-mediated delivery of both XopQ and XopX into rice cells results in induction of rice immune responses. These immune responses are not observed when either protein is individually delivered into rice cells. XopQ-XopX-induced rice immune responses are not observed with a XopX mutant that is defective in 14-3-3 binding. Yeast two-hybrid, bimolecular fluorescence complementation and co-immunoprecipitation assays indicate that XopQ and XopX interact with each other. A screen for Xanthomonas effectors that can suppress XopQ-XopX-induced rice immune responses led to the identification of five effectors, namely XopU, XopV, XopP, XopG and AvrBs2, that could individually suppress these immune responses. These results suggest a complex interplay of Xanthomonas T3SS effectors in suppression of both pathogen-triggered immunity and effector-triggered immunity to promote virulence on rice.
稻黄单胞菌 pv. 稻致病变种利用几种类型 III 分泌系统（T3SS）分泌的效应子，即 XopN、XopQ、XopX 和 XopZ，来抑制水稻对细胞壁降解酶处理后诱导的免疫反应。在这里，我们表明 T3SS 分泌的效应子 XopX 与水稻 14-3-3 蛋白的八个中的两个相互作用。XopX 中与 14-3-3 结合缺陷的突变体也在抑制免疫反应方面存在缺陷，这表明与 14-3-3 蛋白的相互作用是抑制宿主先天免疫所必需的。然而，农杆菌介导的将 XopQ 和 XopX 都递送到水稻细胞中会导致水稻免疫反应的诱导。当单独将任何一种蛋白质递送到水稻细胞中时，不会观察到这些免疫反应。在 XopX 中与 14-3-3 结合缺陷的突变体中，XopQ-XopX 诱导的水稻免疫反应不会被观察到。酵母双杂交、双分子荧光互补和共免疫沉淀测定表明 XopQ 和 XopX 相互作用。筛选可以抑制 XopQ-XopX 诱导的水稻免疫反应的黄单胞菌效应子，导致鉴定出五个效应子，即 XopU、XopV、XopP、XopG 和 AvrBs2，它们可以单独抑制这些免疫反应。这些结果表明，黄单胞菌 T3SS 效应子在抑制病原菌触发的免疫和效应子触发的免疫方面存在复杂的相互作用，以促进在水稻上的毒力。
