Janousek Bohuslav, Gogela Roman, Bacovsky Vaclav, Renner Susanne S
Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 61265 Brno, Czech Republic.
Department of Biology, Washington University, Saint Louis, MO, USA.
Philos Trans R Soc Lond B Biol Sci. 2022 May 9;377(1850):20210294. doi: 10.1098/rstb.2021.0294. Epub 2022 Mar 21.
Microscopically dimorphic sex chromosomes in plants are rare, reducing our ability to study them. One difficulty has been the paucity of cultivatable species pairs for cytogenetic, genomic and experimental work. Here, we study the newly recognized sisters and , both with large Y chromosomes as we here show for . We built genetic maps for male and female using a full-sibling family, inferred gene sex-linkage, and, with transcriptome data, tested whether X- and Y-alleles group by species or by sex. Most sex-linked genes for which we could include outgroups grouped the X- and Y-alleles by species, but some 10% instead grouped the two species' X-alleles. There was no relationship between XY synonymous-site divergences in these genes and gene position on the non-recombining part of the X, suggesting recombination arrest shortly before or after species divergence, here dated to about 3.6 Ma. and are the species pair with the most heteromorphic sex chromosomes in vascular plants (the condition in their sister remains unknown), and future work could use them to study mechanisms of Y chromosome enlargement and parallel degeneration, or to test Haldane's rule about lower hybrid fitness in the heterogametic sex. This article is part of the theme issue 'Sex determination and sex chromosome evolution in land plants'.
植物中微观上呈二态性的性染色体很罕见，这降低了我们对其进行研究的能力。其中一个困难在于缺乏可用于细胞遗传学、基因组学和实验工作的可培养物种对。在这里，我们研究了新确认的姊妹物种 和 ，正如我们在此对 所展示的那样，它们都有大的Y染色体。我们利用一个全同胞家系构建了雄性和雌性 的遗传图谱，推断了基因的性连锁关系，并利用 的转录组数据，测试X和Y等位基因是按物种还是按性别分组。对于我们能够纳入外类群的大多数性连锁基因，其X和Y等位基因按物种分组，但约10%的基因反而将两个物种的X等位基因归为一组。这些基因中XY同义位点的分歧与X染色体非重组部分上的基因位置之间没有关系，这表明在物种分化之前或之后不久重组就停止了，这里估计约为360万年前。 和 是维管植物中性染色体异形程度最高的物种对（它们姊妹物种的情况未知），未来的研究可以利用它们来研究Y染色体增大和平行退化的机制，或者检验霍尔丹关于异配性别杂种适应性较低的法则。本文是主题为“陆地植物的性别决定和性染色体进化”的一部分。
