N6‐Methyladenosine mRNA methylation is important for salt stress tolerance in Arabidopsis

Abstract

As the most abundant internal modification in mRNA, N6 -methyladenosine (m6 A) methylation of RNA is emerging as a new layer of epitranscriptomic gene regulation in cellular processes, including embryo development, flowering time control, microspores generation, and fruit-ripening, in plants. However, the cellular role of m6 A in plant response to environmental stimuli remains largely unexplored. In this study, we show that m6 A methylation plays an important role in salt stress tolerance in Arabidopsis. All mutants of m6 A writer components, including MTA, MTB, VIRILIZER (VIR), and HAKAI, displayed salt-sensitive phenotypes in an m6 A-dependent manner. The vir mutant, in which the m6 A level was most highly reduced, exhibited salt-hypersensitive phenotypes. Analysis of m6 A methylome in the vir mutant revealed a transcriptome-wide loss of m6 A modification in the 3'UTR. We further demonstrated that VIR-mediated m6 A methylation modulates reactive oxygen species homeostasis by negatively regulating the mRNA stability of several salt stress negative regulators, including ATAF1, GI, and GSTU17, via affecting 3'UTR lengthening linked to alternative polyadenylation. Our results highlight the important role played by epitranscriptomic mRNA methylation in the salt stress response of Arabidopsis and indicate a strong link between m6 A methylation and 3'UTR length and mRNA stability during stress adaptation.