The m6A reader SlYTH1 regulates flavor-related volatiles biosynthesis via affecting mRNA stability and translation in tomato fruit

Abstract N 6-methyladenosine (m6A) is the most prevalent RNA epigenetic modification in eukaryotes, catalyzed by methyltransferases (writers), removed by demethylases (erasers), and recognized by binding proteins (readers). While previous studies have established the essential role of m6A homeostasis in regulating fruit ripening, the post-transcriptional mechanisms underlying m6A-mediated quality trait formation remain poorly understood. Following our recent discovery of a YT521B homology (YTH) domain-containing m6A reader gene, SlYTH2, as a translational repressor for the production of tomato (Solanum lycopersicum) aroma volatiles, we reveal here a distinct regulatory effect through knockout of SlYTH1, which specifically reduces flavor-related volatiles in tomato fruit without affecting the days from anthesis to fruit color break, ethylene production, or firmness. Notably, this finding contrasts with the role of SlYTH2, which negatively regulates fruit aroma, highlighting the opposing effects of SlYTH1 and SlYTH2 in modulating fruit aroma. Mechanistically, SlYTH1 binds to m6A-modified mRNA targets both in vitro and in vivo, performing dual roles in maintaining mRNA stability and promoting translation. Specifically, the loss of SlYTH1 function accelerated the decline in the transcript and protein levels of two key targets, SlBCAT1 and SlTNH1, which are essential for volatile biosynthesis. This study provides insights into the role of m6A modification in regulating fruit flavor quality during ripening. Furthermore, it identifies SlYTH1 as a potential genetic target for improving fruit flavor without altering the timing of ripening.