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

The biological functions of the epitranscriptomic modification N-methyladenosine (mA) in plants are not fully understood. CPSF30-L is a predominant isoform of the polyadenylation factor CPSF30 and consists of CPSF30-S and an mA-binding YTH domain. Little is known about the biological roles of CPSF30-L and the molecular mechanism underlying its mA-binding function in alternative polyadenylation. Here, we characterized CPSF30-L as an Arabidopsis mA reader whose mA-binding function is required for the floral transition and abscisic acid (ABA) response. We found that the mA-binding activity of CPSF30-L enhances the formation of liquid-like nuclear bodies, where CPSF30-L mainly recognizes mA-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 mA-driven phase separation and polyadenylation in plants.