DNA methylation reprogramming during plant sexual reproduction?

Chromatin modifications including histone marks and DNA methylation restrict the transcriptional repertoire and participate in cell fate establishment. Conservation of modified chromatin states through cell division and their inheritance through meiosis create mitotic and trans-generational forms of epigenetic memory, respectively. This lies in apparent contradiction with the requirement to reset cell-fate instructive chromatin states between generations. Although DNA methylation is reset in mammals, its resetting in plants remains controversial, and several lines of evidence support trans-generational inheritance of DNA methylation. Based on recent reports we propose that DNA demethylation during female gametogenesis is followed by DNA remethylation during early embryo development. We propose that this reprogramming event is achieved through interplay between active and passive mechanisms that involve both DNA demethylation and de novo DNA methylation. Copyright 2010 Elsevier Ltd. All rights reserved.