Abstract
Genomic imprinting is an essential epigenetic process that controls the size of seeds in flowering plants. In Arabidopsis, DEMETER activates the maternal copy of the imprinted MEDEA Polycomb gene. In this issue of Cell, Gehring et al. (2006) demonstrate that this activation involves DNA demethylation of MEDEA by DEMETER. Remarkably, they also find that silencing of the paternal MEDEA allele is independent of DNA methylation and is controlled by maternal expression of MEDEA itself.