DNA Demethylation and Gene Imprinting in Flowering Plants

Abstract

Gene imprinting is the monoallelic gene expression in a parent- of-origin-dependent manner that results from differential epigenetic states of the parental alleles. It is important for plant reproduction, in particular, the develop- ment of endosperm that provides nutrients to the embryo in flowering plants. With a few exceptions, all known plant gene imprinting occurs in the endosperm. The distinctive mechanisms of gene imprinting in the endosperm involve DNA demeth- ylation and histone modifications. Notably, regulation of many imprinted genes begins prior to fertilization of the central cell member of the female gametophyte, where active DNA demethylation, the process which removes DNA methylation independently of DNA replication, is initiated by a plant-specific DNA demethylase. Recent genome-wide studies revealed the “imprintome”—the whole set of imprinted genes—in Arabidopsis thaliana endosperm. From the evolutionary point of view, lines of evidence suggest that both double fertilization and gene imprinting might have coevolved in flowering plants for their reproductive success.