School of Life Sciences, University of Warwick, Wellesbourne Campus, Coventry CV35 9EF, UK.
Plant Cell Physiol. 2012 May;53(5):817-23. doi: 10.1093/pcp/pcs052. Epub 2012 Apr 13.
Monoecious flowering plants produce both microgametophytes (pollen) and megagametophytes (embryo sacs) containing the male and female gametes, respectively, which participate in double fertilization. Much is known about cellular and developmental processes giving rise to these reproductive structures and the formation of gametes. However, little is known about the role played by changes in the epigenome in dynamically shaping these defining events during plant sexual reproduction. This has in part been hampered by the inaccessibility of these structures-especially the female gametes, which are embedded within the female reproductive tissues of the plant sporophyte. However, with the recent development of new cellular isolation technologies that can be coupled to next-generation sequencing, a new wave of epigenomic studies indicate that an intricate epigenetic regulation takes place during the formation of male and female reproductive lineages. In this mini review, we assess the fast growing body of evidence for the epigenetic regulation of the developmental fate and function of plant gametes. We describe how small interfereing RNAs and DNA methylation machinery play a part in setting up unique epigenetic landscapes in different gametes, which may be responsible for their different fates and functions during fertilization. Collectively these studies will shed light on the dynamic epigenomic landscape of plant gametes or 'epigametes' and help to answer important unresolved questions on the sexual reproduction of flowering plants, especially those underpinning the formation of two products of fertilization, the embryo and the endosperm.
雌雄同体的开花植物分别产生小配子体（花粉）和大配子体（胚囊），分别包含雄性和雌性配子，它们参与双受精。人们对产生这些生殖结构和配子形成的细胞和发育过程有了很多了解。然而，对于表观基因组在动态塑造植物有性生殖过程中这些决定性事件中的作用，人们知之甚少。这在一定程度上受到这些结构的不可及性的阻碍——特别是雌性配子，它们嵌入植物孢子体的雌性生殖组织中。然而，随着新的细胞分离技术的发展，这些技术可以与下一代测序相结合，新一轮的表观基因组研究表明，在雄性和雌性生殖谱系的形成过程中存在着复杂的表观遗传调控。在这篇小综述中，我们评估了关于植物配子发育命运和功能的表观遗传调控的快速增长的证据体。我们描述了小干扰 RNA 和 DNA 甲基化机制如何在不同的配子中发挥作用，建立独特的表观遗传景观，这可能是它们在受精过程中不同命运和功能的原因。这些研究将共同揭示植物配子或“epigametes”的动态表观基因组景观，并有助于回答有关有花植物有性生殖的重要未解决问题，特别是那些支持胚胎和胚乳这两种受精产物形成的问题。
