Arabidopsis N6-methyladenosine reader CPSF30-L recognizes FUE signal to control polyadenylation site choice in liquid-like nuclear body

Abstract The biological functions of epitranscriptomic modification N6-methyladenosine (m6A) in plants have not been fully understood. CPSF30-L is a predominant isoform of polyadenylation factor CPSF30 and consists of CPSF30-S and m6A-binding YTH domain. Little is known about the biological roles of CPSF30-L and the molecular mechanism underlying its m6A binding function in alternative polyadenylation (APA). Here we characterized CPSF30-L as an Arabidopsis m6A reader whose m6A binding function is required for floral transition and abscisic acid (ABA) response. We found the m6A binding activity enhances the formation of liquid-like CPSF30-L nuclear bodies, where CPSF30-L mainly recognizes m6A-modified far upstream element (FUE) to control polyadenylation site choice. Disruption of CPSF30-L lengthens 3' untranslated region (3' UTR) of three CPSF30-L binding transcripts related with phenotypes, thereby accelerating their mRNA degradation and leading to late flowering and ABA hypersensitivity. This study uncovers a new molecular mechanism for m6A-driven phase separation and polyadenylation in plants.