Methylation and demethylation of the Arabidopsis genome

▶ Active DNA methylation is mediated by MET1, CMT3, DRM1 and DRM2. ▶ It also requires other gene products (DDM1, DRD1, VIM1, VIM2, VIM3 and HOG1). ▶ Loss of methylation results in loss of methylation of the pericentromeric heterochromatin. ▶ Active demethylation is mediated by four glycosylases but the effects are subtle. ▶ Pollen and endosperm development involve loss of DNA methylation.