FIONA1-mediated mRNA m 6 A methylation regulates the response of Arabidopsis to salt stress.

N 6 -methyladenosine (m 6 A) is an mRNA modification widely found in eukaryotes and plays a crucial role in plant development and stress responses. FIONA1 (FIO1) is a recently identified m 6 A methyltransferase that regulates Arabidopsis (Arabidopsis thaliana) floral transition; however, its role in stress response remains unknown. In this study, we demonstrate that FIO1-mediated m 6 A methylation plays a vital role in salt stress response in Arabidopsis. The loss-of-function fio1 mutant was sensitive to salt stress. Importantly, the complementation lines expressing the wild-type FIO1 exhibited the wild-type phenotype, whereas the complementation lines expressing the mutant FIO1 m , in which two critical amino acid residues essential for methyltransferase activity were mutated, did not recover the wild-type phenotype under salt stress, indicating that the salt sensitivity is associated with FIO1 methyltransferase activity. Furthermore, FIO1-mediated m 6 A methylation regulated ROS production and affected the transcript level of several salt stress-responsive genes via modulating their mRNA stability in an m 6 A-dependent manner in response to salt stress. Importantly, FIO1 is associated with salt stress response by specifically targeting and differentially modulating several salt stress-responsive genes compared with other m 6 A writer. Collectively, our findings highlight the molecular mechanism of FIO1-mediated m 6 A methylation in the salt stress adaptation.