Epigenetic mechanisms of sexual reproduction in Angiosperms

Epigenetic mechanisms, such as DNA methylation, RNA interference, posttranslational histone modifications and rearrangements of chromatin structure play an important role during genome reprogramming in both animals and plants. The correct epigenetic pattern of eu- and heterochromatin marks allows for maintaining chromatin in an active or transcriptionally silenced state. In the life cycle of angiosperms, epigenetic mechanisms participate in genome reprogramming during: 1) differentiation of sporophyte cells into spore mother cells (SMC) that undergo meiosis, 2) development of female and male gametophytes, within which the gametes differentiate and 3) after double fertilization during the embryo and endosperm development. SMC speciation and control of meiosis, followed by reprogramming of the sperm cells and egg cell genome, are non-cell-autonomous and require RdDM pathway. These processes involve companion cells, which produce „mobile” siRNAs signal molecules. Epigenetic control of gene expression through siRNAs also participates in maintenance of gametes and embryo genome integrity and in the parental imprinting.