Eastern China Conservation Centre for Wild Endangered Plant Resources, Shanghai Chenshan Botanical Garden, Shanghai, 201602, China.
Laboratory of Systematic Evolution and Biogeography of Woody Plants, School of Ecology and Nature Conservation, Beijing Forestry University, Beijing, 100083, China.
Nat Commun. 2024 Aug 12;15(1):6893. doi: 10.1038/s41467-024-51158-3.
Polyploidization presents an unusual challenge for species with sex chromosomes, as it can lead to complex combinations of sex chromosomes that disrupt reproductive development. This is particularly true for allopolyploidization between species with different sex chromosome systems. Here, we assemble haplotype-resolved chromosome-level genomes of a female allotetraploid weeping willow (Salix babylonica) and a male diploid S. dunnii. We show that weeping willow arose from crosses between a female ancestor from the Salix-clade, which has XY sex chromosomes on chromosome 7, and a male ancestor from the Vetrix-clade, which has ancestral XY sex chromosomes on chromosome 15. We find that weeping willow has one pair of sex chromosomes, ZW on chromosome 15, that derived from the ancestral XY sex chromosomes in the male ancestor of the Vetrix-clade. Moreover, the ancestral 7X chromosomes from the female ancestor of the Salix-clade have reverted to autosomal inheritance. Duplicated intact ARR17-like genes on the four homologous chromosomes 19 likely have contributed to the maintenance of dioecy during polyploidization and sex chromosome turnover. Taken together, our results suggest the rapid evolution and reversion of sex chromosomes following allopolyploidization in weeping willow.
多倍体化对具有性染色体的物种构成了一个特殊的挑战，因为它可能导致性染色体的复杂组合，从而破坏生殖发育。对于来自不同性染色体系统的物种之间的异源多倍体化来说，情况尤其如此。在这里，我们组装了一个雌性异源四倍体垂柳（Salix babylonica）和一个雄性二倍体 S. dunnii 的单倍型解析染色体水平基因组。我们表明，垂柳是由一个具有 XY 性染色体的雌性祖先（第 7 号染色体）和一个具有 XY 性染色体的雄性祖先（第 15 号染色体）杂交产生的，后者来自 Vetrix 分支，而前者来自 Salix 分支。我们发现垂柳有一对性染色体，ZW，位于第 15 号染色体上，这对性染色体来自 Vetrix 分支雄性祖先的原始 XY 性染色体。此外，来自 Salix 分支雌性祖先的 7X 染色体已经退回到常染色体遗传。四个同源染色体 19 上完整的 ARR17 样基因的重复可能有助于在多倍体化和性染色体转变过程中维持雌雄异株。总的来说，我们的结果表明，在垂柳中，异源多倍体化后性染色体迅速进化和逆转。
