DNA METHYLTRANSFERASE 1 is involved in (m)CG and (m)CCG DNA methylation and is essential for sporophyte development in Physcomitrella patens.

DNA methylation has a crucial role in plant development regulating gene expression and silencing of transposable elements. Maintenance DNA methylation in plants occurs at symmetrical (m)CG and (m)CHG contexts ((m) = methylated) and is maintained by DNA METHYLTRANSFERASE 1 (MET1) and CHROMOMETHYLASE (CMT) DNA methyltransferase protein families, respectively. While angiosperm genomes encode for several members of MET1 and CMT families, the moss Physcomitrella patens, serving as a model for early divergent land plants, carries a single member of each family.

A single CMT methyltransferase homolog is involved in CHG DNA methylation and development of Physcomitrella patens.

C-5 DNA methylation is an essential mechanism controlling gene expression and developmental programs in a variety of organisms. Though the role of DNA methylation has been intensively studied in mammals and Arabidopsis, little is known about the evolution of this mechanism. The chromomethylase (CMT) methyltransferase family is unique to plants and was found to be involved in DNA methylation in Arabidopsis, maize and tobacco.