Methylation and nitric oxide (NO)-based S-nitrosylation are highly conserved protein posttranslational modifications that regulate diverse biological processes. In higher eukaryotes, PRMT5 catalyzes Arg symmetric dimethylation, including key components of the spliceosome. The Arabidopsis prmt5 mutant shows severe developmental defects and impaired stress responses. However, little is known about the mechanisms regulating the PRMT5 activity. Here, we report that NO positively regulates the PRMT5 activity through S-nitrosylation at Cys-125 during stress responses. In prmt5-1 plants, a PRMT5^C125S transgene, carrying a non-nitrosylatable mutation at Cys-125, fully rescues the developmental defects, but not the stress hypersensitive phenotype and the responsiveness to NO during stress responses. Moreover, the salt-induced Arg symmetric dimethylation is abolished in PRMT5^C125S/prmt5-1 plants, correlated to aberrant splicing of pre-mRNA derived from a stress-related gene. These findings define a mechanism by which plants transduce stress-triggered NO signal to protein methylation machinery through S-nitrosylation of PRMT5 in response to environmental alterations.

甲基化和基于一氧化氮（NO）的S-亚硝基化是高度保守的蛋白质翻译后修饰，可调节多种生物过程。在高级真核生物中，PRMT5催化Arg对称二甲基化，包括剪接体的关键成分。的拟南芥PRMT5突变体显示了严重的发育缺陷和受损的应激反应。但是，关于调节PRMT5活性的机制知之甚少。在这里，我们报告说，在应激反应期间，NO通过Cys-125上的S-亚硝基化正调控PRMT5的活性。在prmt5-1工厂中，PRMT5 ^C125S转基因在Cys-125处带有一个非亚硝基化突变，可完全挽救发育缺陷，但不能挽救应激超敏表型和应激反应中对NO的反应性。此外，盐诱导的Arg对称的二甲基化在PRMT5 ^C125S / prmt5-1植物中被取消，这与源自胁迫相关基因的pre-mRNA的异常剪接有关。这些发现确定了一种机制，通过该机制，植物响应于环境变化，通过PRMT5的S-亚硝基化将应力触发的NO信号转导至蛋白质甲基化机制。