Gene imprinting is the expression of certain genes depending on their parent-of-origin, essential for normal development in both flowering plants and placental mammals. In plants, imprinting is mostly confined to the endosperm of the developing seed. DNA demethylation of specific loci in the female gametophyte is central to the control of this epigenetically regulated process. As such, DNA demethylation is essential during plant development due to its role in the regulation of gene imprinting. Our recent data, together with our collaborators in Daniel Zilberman’s lab, support this, but also reveal a more basal function for this process. DNA demethylation by DME seems to primarily regulate the activity of transposable elements, in order to protect the genomic integrity of progeny. The monoallelic silencing of genes whose expression is controlled by TEs, if conferring a selection advantage, may have led to the evolution of imprinted loci in flowering plant endosperm.