Transgenerational Transmission of Epigenetic Marks During Reproduction in .

Epigenetics has described non-DNA sequence-based transgenerational inheritance, in which phenotypic traits acquired over a lifetime by parents are passed to their progeny across several generations. Transgenerational epigenetic inheritance may be achieved by transmitting repressive epigenetic marks such as DNA methylation and histone 3 lysine 27 trimethylation (H3K27me3) in parental chromatin through sexual reproduction. In general, with infrequent exceptions, epigenetically modified architectures in parental chromatin are extensively erased by reprogramming during reproduction, leaving little possibility of being inherited by offspring. In comparison, plants exhibit transgenerational epigenetic inheritance with relatively greater frequency, although the underlying molecular mechanisms have remained unclear. Recent studies with the flowering plant () have identified plant-specific mechanisms enabling the transgenerational transmission of epigenetic marks during reproduction. achieves chromatin methylation through the small interfering RNA (siRNA)-directed DNA methylation (RdDM) pathways. In addition, Polycomb repressive complex 2 (PRC2) catalyzes H3K27me3 deposition on exchangeable histone variants during reproduction in a plant-specific manner. This review describes recent progress in research of transgenerational epigenetic inheritance, focusing on transmitting epigenetic marks through reproduction steps: meiosis, gametogenesis, and embryogenesis.