Proper transcriptome reprogramming is critical for hosts to launch an effective defense response upon pathogen attack. How immune-related genes are regulated at the posttranscriptional level remains elusive. We demonstrate here that P-bodies, the non-membranous cytoplasmic ribonucleoprotein foci related to 5'-to-3' mRNA decay, are dynamically modulated in plant immunity triggered by microbe-associated molecular patterns (MAMPs). The DCP1-DCP2 mRNA decapping complex, a hallmark of P-bodies, positively regulates plant MAMP-triggered responses and immunity against pathogenic bacteria. MAMP-activated MAP kinases directly phosphorylate DCP1 at the serine237 residue, which further stimulates its interaction with XRN4, an exonuclease executing 5'-to-3' degradation of decapped mRNA. Consequently, MAMP treatment potentiates DCP1-dependent mRNA decay on a specific group of MAMP-downregulated genes. Thus, the conserved 5'-to-3' mRNA decay elicited by the MAMP-activated MAP kinase cascade is an integral part of plant immunity. This mechanism ensures a rapid posttranscriptional downregulation of certain immune-related genes that may otherwise negatively impact immunity.

中文翻译：

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拟南芥免疫中加工体动力学和mRNA衰变的编排。

正确的转录组重编程对于宿主在病原体发作时启动有效的防御反应至关重要。在转录后水平如何调节免疫相关基因仍然不清楚。我们在这里证明P体，与5'到3'mRNA衰变相关的非膜细胞质核糖核蛋白焦点，在微生物相关分子模式（MAMPs）触发的植物免疫中被动态调节。DC的DCP1-DCP2 mRNA脱盖复合物是P体的标志，可正向调节植物MAMP触发的反应和对病原菌的免疫力。MAMP激活的MAP激酶在丝氨酸237残基上直接磷酸化DCP1，这进一步刺激了它与XRN4的相互作用，XRN4是一种核酸外切酶，对脱帽的mRNA进行5'到3'降解。所以，MAMP处理可增强一组特定的MAMP下调基因的DCP1依赖性mRNA衰减。因此，由MAMP活化的MAP激酶级联反应引起的保守的5'至3'mRNA衰减是植物免疫力的组成部分。该机制确保某些免疫相关基因的转录后快速下调，否则可能会对免疫产生负面影响。