Grape DNA methyltransferase VvMET2b overexpression increases genome-wide methylation and enhances seed salt tolerance

• VvMET2b enhanced seed salt tolerance • VvMET2b increased DNA methylation levels under salt stress • VvMET2b modulated salt tolerance through DNA methylation • VvMET2b modulated the expression of transcription factors and hormone-related genes MET1 encodes DNA methyltransferase 1, which is increasingly being identified as a major regulator of abiotic stress responses and adaptation. To explore the function of DNA methyltransferase 1 in salt stress, we cloned a grape ( Vitis vinifera L.) MET1 subfamily gene, VvMET2b, and overexpressed it into A. thaliana . The phenotypic analysis of transgenic Arabidopsis revealed that Vv MET2b improved seed germination and seedling survival under NaCl treatment. Detailed methylome analysis revealed that Vv MET2b increased the global methylation level of transgenic plants and altered the quantity of differentially methylated regions (DMRs) and DNA methylation types. Comprehensive transcriptome analyses indicated that many transcription factors, such as NACs, MYBs, and WRKYs were differentially expressed in VvMET2bOE plants under salt stress. VvMET2b overexpression induced the expression of cytokinin negative regulator type-A ARRs , the transmembrane transporter KAT1 , inhibited the expression of MYB6 , and the up-regulated expression of auxin-related genes Aux/IAAs and down-regulated expression of GH3s, expansin EXPA17 and tonoplast aquaporin TIP2 were mitigated. VvMET2b altered DNA methylation level of MYB6 , TIP2 and EXPA17 and thereby may regulate the expression of these genes. Taken together, VvMET2b may regulate seed salt tolerance through DNA methylation changes and certain key gene expression.