Proteasome subunit RPT2a promotes PTGS through repressing RNA quality control in Arabidopsis. Proteasome subunit RPT2a promotes PTGS through repressing RNA quality control in Arabidopsis

RNA quality control (RQC) and post-transcriptional gene silencing (PTGS) target and degrade aberrant endogenous RNAs and foreign RNAs, contributing to homeostasis of cellular RNAs. In plants, RQC and PTGS compete for foreign and selected endogenous RNAs; however, little is known about the mechanism interconnecting the two pathways. Using a reporter system designed for monitoring PTGS, we revealed that the 26S proteasome subunit RPT2a enhances transgene PTGS by promoting the accumulation of transgene-derived short interfering RNAs without affecting their biogenesis. RPT2a physically associated with a subset of RQC components and downregulated the protein level. Overexpression of the RQC components interfered with transgene silencing, and impairment of the RQC machinery reinforced transgene PTGS attenuated by rpt2a. Overall, we demonstrate that the 26S proteasome subunit RPT2a promotes PTGS by repressing the RQC machinery to control foreign RNAs. Overall design: Small RNA profiling in PORI and PORI/rpt2a was analyzed by small RNA-sequencing.

RNA质量控制（RNA quality control, RQC）与转录后基因沉默（post-transcriptional gene silencing, PTGS）可靶向并降解异常内源RNA及外源RNA，对维持细胞RNA稳态具有重要作用。在植物中，RQC与PTGS会竞争外源RNA与部分内源RNA，但目前学界对二者之间的关联机制仍知之甚少。本研究借助专为监测PTGS开发的报告系统，发现26S蛋白酶体亚基RPT2a可在不影响短干扰RNA（short interfering RNAs）生物发生的前提下，通过促进转基因来源的短干扰RNA积累，增强转基因的PTGS效应。RPT2a可与部分RQC组分发生物理互作，并下调其蛋白表达水平。过表达RQC组分会干扰转基因沉默，而RQC通路受损则可强化因rpt2a功能缺陷所减弱的转基因PTGS。综上，本研究证实26S蛋白酶体亚基RPT2a可通过抑制RQC通路以调控外源RNA，从而促进PTGS。实验设计：通过小RNA测序（small RNA-sequencing）分析PORI与PORI/rpt2a中的小RNA表达谱。