ECT8 , an mRNA m 6 A reader, enhances salt stress tolerance by modulating mRNA stability in Arabidopsis

Abstract N6‐methyladenosine (m 6 A), the most prevalent modification found in eukaryotic mRNAs, is recognized and interpreted by m 6 A‐binding proteins called m 6 A readers. The EVOLUTIONARILY CONSERVED C‐TERMINAL REGION (ECT) proteins have increasingly been identified as m 6 A readers in plants. A recent study has demonstrated that the loss‐of‐function ect8 mutant is sensitive to salt stress by enhancing the stability of negative salt stress regulators in Arabidopsis ( Arabidopsis thaliana ). In this study, we generated and analyzed the ECT8‐overexpressing transgenic Arabidopsis plants to further explore the function of ECT8 in salt stress response. The electrophoretic mobility shift assay in vitro showed that ECT8 binds to the m 6 A‐modified synthetic RNAs, preferring UGUm 6 AA and UACm 6 AGA motifs over the GGm 6 ACU motif. Contrary to the ect8 mutant exhibiting salt hypersensitivity by enhancing the stability of salt stress negative regulators, the ECT8‐overexpressing transgenic Arabidopsis plants displayed salt tolerance by increasing the stability and expression levels of salt stress positive regulators. Moreover, RNA‐immunoprecipitation assay demonstrated that ECT8 binds to the m 6 A‐modified salt stress‐responsive mRNAs in planta . Collectively, our current and previous findings highlight that ECT8‐mediated stabilization and destabilization of the genes encoding salt stress positive or negative regulators, respectively, contribute to the salt stress tolerance of Arabidopsis.