In plants, DNA methylation in different sequence contexts (CG, CHG and CHH, where H is A, T, or C) is maintained by different DNA methyltransferases. In Arabidopsis thaliana, the maintenance of symmetric CG methylation is catalyzed by METHYLTRANSFERASE 1 (MET1), whereas CHROMOMETHYLASE 3 (CMT3) is mainly responsible for the maintenance of CHG methylation.