Phytophthora infestans is a destructive oomycete that causes the late blight of potato and tomato worldwide. It secretes numerous small proteins called effectors in order to manipulate host cell components and suppress plant immunity. Identifying the targets of these effectors is crucial for understanding P. infestans pathogenesis and host plant immunity. In this study, we show that the virulence RXLR effector Pi23014 of P. infestans targets the host nucleus and chloroplasts. By using a liquid chromatogrpahy-tandem mass spectrometry assay and co-immunoprecipitation assasys, we show that it interacts with NbRBP3a, a putative glycine-rich RNA-binding protein. We confirmed the co-localization of Pi23014 and NbRBP3a within the nucleus, by using bimolecular fluorescence complementation. Reverse transcription-quantitative PCR assays showed that the expression of NbRBP3a was induced in Nicotiana benthamiana during P. infestans infection and the expression of marker genes for multiple defence pathways were significantly down-regulated in NbRBP3-silenced plants compared with GFP-silenced plants. Agrobacterium tumefaciens-mediated transient overexpression of NbRBP3a significantly enhanced plant resistance to P. infestans. Mutations in the N-terminus RNA recognition motif (RRM) of NbRBP3a abolished its interaction with Pi23014 and eliminated its capability to enhance plant resistance to leaf colonization by P. infestans. We further showed that silencing NbRBP3 reduced photosystem II activity, reduced host photosynthetic efficiency, attenuated Pi23014-mediated suppression of cell death triggered by P. infestans pathogen-associated molecular pattern elicitor INF1, and suppressed plant immunity.

中文翻译：

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致病疫霉 RXLR 效应子 Pi23014 靶向宿主 RNA 结合蛋白 NbRBP3a 抑制植物免疫

致病疫霉是一种破坏性卵菌，会导致全世界马铃薯和番茄晚疫病。它分泌大量称为效应子的小蛋白质，以操纵宿主细胞成分并抑制植物免疫。识别这些效应子的靶标对于了解致病疫霉发病机制和宿主植物免疫至关重要。在这项研究中，我们发现致病疫霉的毒力 RXLR 效应子 Pi23014靶向宿主细胞核和叶绿体。通过使用液相色谱-串联质谱分析和免疫共沉淀分析，我们证明它与 NbRBP3a（一种假定的富含甘氨酸的 RNA 结合蛋白）相互作用。我们通过使用双分子荧光互补证实了 Pi23014 和 NbRBP3a 在细胞核内的共定位。逆转录定量PCR检测表明，在致病疫霉感染期间，本塞姆氏烟草中NbRBP3a的表达被诱导，并且与GFP沉默的植物相比， NbRBP3沉默的植物中多种防御途径的标记基因的表达显着下调。根癌农杆菌介导的NbRBP3a瞬时过表达显着增强了植物对致病疫霉的抗性。NbRBP3a N 端 RNA 识别基序 (RRM) 的突变消除了其与 Pi23014 的相互作用，并消除了其增强植物对致病疫霉叶片定殖的抗性的能力。我们进一步表明，沉默NbRBP3会降低光系统 II 活性，降低宿主光合效率，减弱 Pi23014 介导的致病疫霉病原体相关分子模式激发子INF1引发的细胞死亡抑制，并抑制植物免疫。