背景:基因组大小受自然选择和遗传漂移的影响,遗传漂移作用于多倍体和重复DNA序列的变异。我们假设着丝粒驱动,减数分裂期间着丝粒竞争包含在功能配子中,也可能影响基因组和染色体大小。这种竞争发生在不对称减数分裂中,四种减数分裂产品中只有一种成为配子。如果着丝粒驱动影响染色体大小进化,它也可能影响多倍体二倍体化,多倍体基因组通过染色体重排重组为更像二倍体的功能,包括融合。我们测试了与仅具有对称减数分裂的植物谱系相比,具有不对称减数分裂的植物谱系是否表现出更快的染色体大小进化,由于所有四种减数分裂产品都成为配子,因此缺乏着丝粒驱动。我们还检查了着丝粒组蛋白H3(CENH3)的阳性选择,一种可以抑制着丝粒驱动的蛋白质,在这些不对称谱系中更为频繁。
方法:我们分析了具有不同减数分裂模式的植物组:裸子植物和被子植物的不对称,在苔藓植物中对称,lycophytes,和蕨类植物.我们根据可用的CENH3基因序列和染色体大小数据选择物种。使用Ornstein-Uhlenbeck进化模型和系统发育回归,我们评估了这些进化枝的染色体大小进化率和CENH3阳性选择频率.
结果:我们的分析表明,与对称进化枝相比,具有不对称减数分裂的进化枝具有更高的CENH3阳性选择频率和增加的染色体大小进化率。
结论:我们的发现支持着丝粒驱动加速染色体和基因组大小进化的假设,潜在的影响后多倍体二倍体化的过程。我们提出了一个模型,该模型在单个著名作品中有助于解释对称谱系中染色体大小的稳定性(苔藓植物,lycophytes,和蕨类植物)及其在不对称谱系(裸子植物和被子植物)中的变异性,为未来的植物基因组进化研究奠定了基础。
BACKGROUND: Genome size is influenced by natural selection and genetic drift acting on variations from polyploidy and repetitive DNA sequences. We hypothesized that centromere drive, where centromeres compete for inclusion in the functional gamete during meiosis, may also affect genome and chromosome size. This competition occurs in asymmetric meiosis, where only one of the four meiotic products becomes a gamete. If centromere drive influences chromosome size evolution, it may also impact post-polyploid diploidization, where a polyploid genome is restructured to function more like a diploid through chromosomal rearrangements, including fusions. We tested if plant lineages with asymmetric meiosis exhibit faster chromosome size evolution compared to those with only symmetric meiosis, which lack centromere drive as all four meiotic products become gametes. We also examined if positive selection on centromeric histone H3 (CENH3), a protein that can suppress centromere drive, is more frequent in these asymmetric lineages.
METHODS: We analyzed plant groups with different meiotic modes: asymmetric in gymnosperms and angiosperms, and symmetric in bryophytes, lycophytes, and
ferns. We selected species based on available CENH3 gene sequences and chromosome size data. Using Ornstein-Uhlenbeck evolutionary models and phylogenetic regressions, we assessed the rates of chromosome size evolution and the frequency of positive selection on CENH3 in these clades.
RESULTS: Our analyses showed that clades with asymmetric meiosis have a higher frequency of positive selection on CENH3 and increased rates of chromosome size evolution compared to symmetric clades.
CONCLUSIONS: Our findings support the hypothesis that centromere drive accelerates chromosome and genome size evolution, potenatially also influencing the process of post-polyploid diploidization. We propose a model which in a single famework helps explain the stability of chromosome size in symmetric lineages (bryophytes, lycophytes, and
ferns) and its variability in asymmetric lineages (gymnosperms and angiosperms), providing a foundation for future research in plant genome evolution.