Dynamics of N 6 ‐methyladenosine ( m6A ) under salt stress in poplar and the intrinsic mechanism by which METTL4 ( PagMTC ) enhances salt tolerance

N⁶-methyladenosine (m6A) is the most abundant mRNA modification in organisms. To investigate the dynamics of m6A under salt stress in poplar, 84K poplar (Populus alba × Populus tremula var. glandulosa) and Xiaohei (XH) poplar (Populus simonii × Populus nigra) were subjected to salt treatment followed by MeRIP-seq analysis. The results showed that genes such as ATWRKY40, ATPK19, FDH, and GRX480 exhibited similar methylation and expression patterns in both poplar species under stress. We overexpressed and suppressed PagMTC, a homolog of METTL4 in 84K poplar, and found that the overexpression lines exhibited enhanced salt tolerance. The salt-tolerant genes PagCERK1, PagNCED3a, PagNCED3b, PagCAT2, and PagPOD16 were found to be regulated through PagMTC-mediated hypermethylation, as determined by MeRIP-seq, MeRIP-qPCR, and mRNA stability assay. It was also observed that hypermethylation of genes such as XTH15, CAT2, and AT-HSFB2A after salt stress in wild-type 84K poplar may be mediated by PagMTC. This study reveals the important role of m6A modification in response to salt stress in poplar and also identifies a potential molecular target for breeding trees with enhanced stress tolerance.