University of California Irvine, Irvine, CA 92697, USA.
Department of Integrative Biology, University of California Berkeley, Berkeley, CA, USA.
Philos Trans R Soc Lond B Biol Sci. 2021 Jun 7;376(1826):20200124. doi: 10.1098/rstb.2020.0124. Epub 2021 Apr 19.
We review how epigenetics affect sex chromosome evolution in animals and plants. In a few species, sex is determined epigenetically through the action of Y-encoded small RNAs. Epigenetics is also responsible for changing the sex of individuals through time, even in species that carry sex chromosomes, and could favour species adaptation through breeding system plasticity. The Y chromosome accumulates repeats that become epigenetically silenced which leads to an epigenetic conflict with the expression of Y genes and could accelerate Y degeneration. Y heterochromatin can be lost through ageing, which activates transposable elements and lowers male longevity. Y chromosome degeneration has led to the evolution of meiotic sex chromosome inactivation in eutherians (placentals) and marsupials, and dosage compensation mechanisms in animals and plants. X-inactivation convergently evolved in eutherians and marsupials via two independently evolved non-coding RNAs. In , male X upregulation by the male specific lethal (MSL) complex can spread to neo-X chromosomes through the transposition of transposable elements that carry an MSL-binding motif. We discuss similarities and possible differences between plants and animals and suggest future directions for this dynamic field of research. This article is part of the theme issue 'How does epigenetics influence the course of evolution?'
我们回顾了表观遗传学如何影响动植物性染色体的进化。在少数物种中，性是通过 Y 编码的小 RNA 的作用来表观遗传决定的。表观遗传学也负责通过时间改变个体的性别，即使在携带性染色体的物种中，并且可以通过繁殖系统的可塑性促进物种适应。Y 染色体积累了重复序列，这些重复序列被表观遗传沉默，这导致了与 Y 基因表达的表观遗传冲突，并可能加速 Y 染色体的退化。Y 染色体异染色质可以通过衰老丢失，这会激活转座元件并降低雄性的寿命。Y 染色体的退化导致了真兽类（胎盘类）和有袋类动物减数分裂性染色体失活的进化，以及动物和植物中的剂量补偿机制。X 染色体失活在真兽类和有袋类动物中通过两个独立进化的非编码 RNA 趋同进化。在雄性中，由雄性特异致死（MSL）复合物引起的 X 染色体上调可以通过携带 MSL 结合基序的转座元件的转位，传播到新的 X 染色体上。我们讨论了植物和动物之间的相似性和可能的差异，并为这个充满活力的研究领域提出了未来的方向。本文是主题为“表观遗传学如何影响进化进程？”的特刊的一部分。
