Arabidopsis N6-methyladenosine methyltransferase FIONA1 regulates floral transition by affecting the splicing of FLC and the stability of floral activators SPL3 and SEP3

N 6-methyladenosine (m6A) RNA methylation has been shown to play a crucial role in plant development and floral transition. Two recent studies have identified FIONA1 as an m6A methyltransferase that regulates the floral transition in Arabidopsis through influencing the stability of CONSTANS (CO), SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1), and FLOWERING LOCUS C (FLC). In this study, we confirmed that FIONA1 is an m6A methyltransferase that installs m6A marks in a small group of mRNAs. Furthermore, we show that, in addition to its role in influencing the stability of CO, SOC1, and FLC, FIONA1-mediated m6A methylation influences the splicing of FLC, a key floral repressor, and the stability of SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 3 (SPL3) and SEPALLATA3 (SEP3), floral activators, which together play a vital role in floral transition in Arabidopsis. Our study confirms the function of FIONA1 as an m6A methyltransferase and suggests a close molecular link between FIONA1-mediated m6A methylation and the splicing of FLC and the destabilization of SPL3 and SEP3 in flowering time control.