Cytosine methylation in plants occurs in the mCG, mCHG, and mCHH (where H = A, T, or C) sequence contexts and specific pathways maintain methylation in each one. A recent publication revealed that substantial heterogeneity of methylated cytosine levels exists in the CHG/CHH trinucleotide contexts, which is associated with chromomethyltranferase functions in the maintenance of methylation.