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

The biological functions of the epitranscriptomic modification N6-methyladenosine (m6A) in plants are not fully understood. CPSF30-L is a predominant isoform of the polyadenylation factor CPSF30 and consists of CPSF30-S and an 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. Here, we characterized CPSF30-L as an Arabidopsis m6A reader whose m6A-binding function is required for the floral transition and abscisic acid (ABA) response. We found that the m6A-binding activity of CPSF30-L enhances the formation of liquid-like nuclear bodies, where CPSF30-L mainly recognizes m6A-modified far-upstream elements to control polyadenylation site choice. Deficiency of CPSF30-L lengthens the 3′ untranslated region of three phenotypes-related transcripts, thereby accelerating their mRNA degradation and leading to late flowering and ABA hypersensitivity. Collectively, this study uncovers a new molecular mechanism for m6A-driven phase separation and polyadenylation in plants.