Major CG methylase that methylates chromatin CpG residues and maintains DNA methylation (PubMed:24535433, PubMed:25002488). Plays a major role in genomic imprinting, regulation of embryogenesis and seed viability (PubMed:24535433, PubMed:25002488). Maintains DNA methylation at the FIE1 gene locus in the embryo (PubMed:24535433). a 2'-deoxycytidine in DNA + S-adenosyl-L-methionine = a 5-methyl-2'-deoxycytidine in DNA + H(+) + S-adenosyl-L-homocysteine Expressed in roots and inflorescences (PubMed:14513380). Expressed in roots, panicles, anthers, pistils, endosperm and imbibed embryos (PubMed:18281124). Expressed in tissues containing actively replicating and dividing cells, such as shoot and root meristems (PubMed:24535433). Induced by salt stress, cold stress and drought stress. Non-viable and shrunk seeds, and embryonic lethality when homozygous. Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.