Phytophthora effector PSR1 suppresses small RNA (sRNA)-mediated immunity in plants, but the underlying mechanism remains unknown. Here, we show that Phytophthora suppressor of RNA silencing 1 (PSR1) contributes to the pathogenicity of Phytophthora sojae and specifically binds to three conserved C-terminal domains of the eukaryotic PSR1-Interacting Protein 1 (PINP1). PINP1 encodes PRP16, a core pre-mRNA splicing factor that unwinds RNA duplexes and binds to primary microRNA transcripts and general RNAs. Intriguingly, PSR1 decreased both RNA helicase and RNA-binding activity of PINP1, thereby dampening sRNA biogenesis and RNA metabolism. The PSR1-PINP1 interaction caused global changes in alternative splicing (AS). A total of 5,135 genes simultaneously exhibited mis-splicing in both PSR1-overexpressing and PINP1-silenced plants. AS upregulated many mRNA transcripts that had their introns retained. The high occurrence of intron retention in AS-induced transcripts significantly promoted Phytophthora pathogen infection in Nicotiana benthamiana, and this might be caused by the production of truncated proteins. Taken together, our findings reveal a key role for PINP1 in regulating sRNA biogenesis and plant immunity.

中文翻译：

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疫霉菌效应子 PSR1 劫持宿主前体 mRNA 剪接机制以调节小 RNA 生物发生和植物免疫。

疫霉菌效应子 PSR1 抑制植物中小 RNA (sRNA) 介导的免疫，但其潜在机制仍然未知。在这里，我们表明 Phytophthora suppressor of RNA silencing 1 (PSR1) 有助于大豆疫霉的致病性，并特异性结合真核 PSR1 相互作用蛋白 1 (PINP1) 的三个保守 C 末端结构域。PINP1 编码 PRP16，这是一种核心 pre-mRNA 剪接因子，可解开 RNA 双链体并与初级 microRNA 转录物和一般 RNA 结合。有趣的是，PSR1 降低了 PINP1 的 RNA 解旋酶和 RNA 结合活性，从而抑制了 sRNA 生物合成和 RNA 代谢。PSR1-PINP1 相互作用引起可变剪接 (AS) 的全局变化。在 PSR1 过表达和 PINP1 沉默的植物中，共有 5,135 个基因同时表现出错误剪接。AS 上调了许多保留了内含子的 mRNA 转录物。AS 诱导的转录物中内含子保留的高发生率显着促进了本氏烟草中疫霉病原体的感染，这可能是由截短蛋白的产生引起的。综上所述，我们的研究结果揭示了 PINP1 在调节 sRNA 生物发生和植物免疫方面的关键作用。