Bifunctional DNA glycosylase/lyase, which excises 5-methylcytosine (5-meC) and 5-hydroxymethylcytosine (5-hmeC), leaving an apyrimidinic (AP) site that is subsequently incised by the lyase activity (PubMed:21896764). Is responsible for the demethylation of methylated cytosine residues of Tos17 retrotransposon DNA (PubMed:21896764). Demethylation of Tos17 cytosine residues promotes its transposition (PubMed:21896764). May be involved in seed development (PubMed:21896764). Binds 1 [4Fe-4S] cluster. The cluster does not appear to play a role in catalysis, but is probably involved in the proper positioning of the enzyme along the DNA strand. Expressed in pistils and immature seeds (PubMed:22448681). Expressed a low levels in roots, leaves and anthers (PubMed:22448681). Increased number of wrinkled seeds (PubMed:21896764). Hypermethylation of cytosine residues in the DNA sequence of Tos17 retrotransposons (PubMed:21896764). Belongs to the DNA glycosylase family. DEMETER subfamily.