Centre for Genomics and Biotechnology, Fujian Provincial Key Laboratory of Haixia Applied Plant Systems Biology, Key Laboratory of Genetics, Breeding and Multiple Utilization of Crops, Ministry of Education, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Department of Biology, University of Oxford, Oxford OX1 3RB, UK; Sorbonne Université, CNRS, UMR 7232 Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, 66650 Banyuls-sur-Mer, France.
Curr Biol. 2023 Jun 19;33(12):2504-2514.e3. doi: 10.1016/j.cub.2023.05.046. Epub 2023 Jun 7.
White campion (Silene latifolia, Caryophyllaceae) was the first vascular plant where sex chromosomes were discovered. This species is a classic model for studies on plant sex chromosomes due to presence of large, clearly distinguishable X and Y chromosomes that originated de novo about 11 million years ago (mya), but lack of genomic resources for this relatively large genome (∼2.8 Gb) remains a significant hurdle. Here we report S. latifolia female genome assembly integrated with sex-specific genetic maps of this species, focusing on sex chromosomes and their evolution. The analysis reveals a highly heterogeneous recombination landscape with strong reduction in recombination rate in the central parts of all chromosomes. Recombination on the X chromosome in female meiosis primarily occurs at the very ends, and over 85% of the X chromosome length is located in a massive (∼330 Mb) gene-poor, rarely recombining pericentromeric region (Xpr). The results indicate that the non-recombining region on the Y chromosome (NRY) initially evolved in a relatively small (∼15 Mb), actively recombining region at the end of the q-arm, possibly as a result of inversion on the nascent X chromosome. The NRY expanded about 6 mya via linkage between the Xpr and the sex-determining region, which may have been caused by expanding pericentromeric recombination suppression on the X chromosome. These findings shed light on the origin of sex chromosomes in S. latifolia and yield genomic resources to assist ongoing and future investigations into sex chromosome evolution.
白屈菜（石竹科）是第一个发现性染色体的维管植物。由于存在大约 1100 万年前（mya）新出现的、体积大且易于区分的 X 和 Y 染色体，但缺乏针对这个相对较大基因组（约 28 亿碱基对）的基因组资源，因此该物种成为植物性染色体研究的经典模式生物。在这里，我们报告了白屈菜雌性基因组的组装，该基因组与该物种的性别特异性遗传图谱整合在一起，重点关注性染色体及其进化。分析揭示了高度异质的重组景观，所有染色体的重组率在中央部分都明显降低。雌性减数分裂中的 X 染色体重组主要发生在两端，超过 85%的 X 染色体长度位于一个巨大的（约 330Mb）基因贫乏、很少重组的着丝粒周围区域（Xpr）。结果表明，Y 染色体上的非重组区（NRY）最初是在 q 臂末端一个相对较小（约 15Mb）、活跃重组的区域进化而来的，可能是由于新生 X 染色体的倒位。NRY 大约在 600 万年前通过 Xpr 和性别决定区域之间的连锁扩张，这可能是由于 X 染色体着丝粒周围重组抑制的扩展所致。这些发现揭示了白屈菜性染色体的起源，并提供了基因组资源，以协助正在进行和未来对性染色体进化的研究。
