N6-methyladenosine RNA modification regulates strawberry fruit ripening in an ABA-dependent manner

Abstract

BackgroundEpigenetic marks, such as DNA methylation, play pivotal roles in regulating ripening of both climacteric and non-climacteric fruits. However, it remains unclear whether mRNA m6A methylation, the epitranscriptome, is functionally conserved for ripening control. ResultsHere we show that m6A methylation, which has been revealed to regulate ripening of tomato, a typical climacteric fruit, displays a dramatic change at ripening onset of strawberry, a classical non-climacteric fruit. The m6A modification in the coding sequence (CDS) regions appears to be ripening-specific and tends to stabilize the mRNAs, whereas m6A around the stop codons and within the 3 untranslated regions is generally negatively correlated with the abundance of the mRNAs. We identified thousands of transcripts with m6A hypermethylation in the CDS regions, including those of NCED5, ABAR, and AREB1 in the abscisic acid (ABA) biosynthesis and signaling pathway. We demonstrated that the methyltransferases MTA and MTB are indispensable for normal ripening of strawberry fruit, and MTA-mediated m6A modification promotes mRNA stability of NCED5 and AREB1, while facilitates translation of ABAR. ConclusionOur findings uncover that m6A methylation regulates ripening of non-climacteric strawberry fruit by targeting ABA pathway, which is distinct from that in climacteric tomato fruit.