An mRNA methylase and demethylase regulate sorghum salt tolerance by mediating N-methyladenosine modification

N-methyladenosine (mA) modification is a crucial and widespread molecular mechanism governing plant development and stress tolerance. The specific impact of mA regulation on plants with inherently high salt tolerance remains unclear. Existing research primarily focuses on the overexpression or knockout of individual writer or eraser components to alter mA levels. However, a comprehensive study simultaneously altering overall mA modification levels within the same experiment is lacking. Such an investigation is essential to determine whether opposing changes in mA modification levels exert entirely different effects on plant salt tolerance. In this study, we identified the major writer member mRNA adenosine methylase A (SbMTA) in sorghum (Sorghum bicolor) as critical for sorghum survival. The sbmta mutant exhibits a phenotype characterized by reduced overall mA, developmental arrest, and, ultimately, lethality. Overexpression of SbMTA increased mA levels and salt tolerance, while overexpression of the mA eraser alkylated DNA repair protein AlkB homolog 10B (SbALKBH10B) in sorghum showed the opposite phenotype. Comparative analyses between sorghum with different mA levels reveal that SbMTA- and SbALKBH10B-mediated mA alterations significantly impact the stability and expression levels of genes related to the abscisic acid signaling pathway and growth under salt stress. In summary, this study unveils the intricate relationship between mA modifications and salt tolerance in sorghum, providing valuable insights into how mA modification levels on specific transcripts influence responses to salt stress.