A common feature of eukaryotic centromeres is the presence of large tracts of tandemly arranged repeats, known as satellite DNA. However, these centromeric repeats appear to experience rapid evolution under forces such as molecular drive and centromere drive, seemingly without consequence to the integrity of the centromere. Moreover, blocks of heterochromatin within the karyotype, including the centromere, are hotspots for chromosome rearrangements that may drive speciation events by contributing to reproductive isolation. However, the relationship between the evolution of heterochromatic sequences and the karyotypic dynamics of these regions remains largely unknown. Here, we show that a single conserved satellite DNA sequence in the order Rodentia of the genus Peromyscus localizes to recurrent sites of chromosome rearrangements and heterochromatic amplifications. Peromyscine species display several unique features of chromosome evolution compared to other Rodentia, including stable maintenance of a strict chromosome number of 48 among all known species in the absence of any detectable interchromosomal rearrangements. Rather, the diverse karyotypes of Peromyscine species are due to intrachromosomal variation in blocks of repeated DNA content. Despite wide variation in the copy number and location of repeat blocks among different species, we find that a single satellite monomer maintains a conserved sequence and homogenized tandem repeat structure, defying predictions of molecular drive. The conservation of this satellite monomer results in common, abundant, and large blocks of chromatin that are homologous among chromosomes within one species and among diverged species. Thus, such a conserved repeat may have facilitated the retention of polymorphic chromosome variants within individuals and intrachromosomal rearrangements between species-both factors that have previously been hypothesized to contribute towards the extremely wide range of ecological adaptations that this genus exhibits.

中文翻译：

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着丝粒卫星伴随着白鼠属广泛的核型多样性，违背了分子驱动的预测。

真核着丝粒的一个共同特征是存在大段串联排列的重复序列，称为卫星 DNA。然而，这些着丝粒重复似乎在分子驱动和着丝粒驱动等力的作用下经历了快速进化，似乎对着丝粒的完整性没有影响。此外，核型内的异染色质块（包括着丝粒）是染色体重排的热点，可能通过促进生殖隔离来驱动物种形成事件。然而，异染色质序列的进化与这些区域的核型动态之间的关系仍然很大程度上未知。在这里，我们展示了白鼠属啮齿目中的单个保守卫星 DNA 序列定位于染色体重排和异染色质扩增的重复位点。与其他啮齿目动物相比，Peromyscine 物种显示出染色体进化的几个独特特征，包括在所有已知物种中稳定维持严格的 48 号染色体，而没有任何可检测到的染色体间重排。相反，Peromyscine 物种的不同核型是由于重复 DNA 内容块的染色体内变异造成的。尽管不同物种之间重复块的拷贝数和位置存在很大差异，但我们发现单个卫星单体保持了保守的序列和均质的串联重复结构，这违背了分子驱动的预测。这种卫星单体的保守性导致了共同的、丰富的和大的染色质块，这些染色质在一个物种内和不同物种的染色体之间是同源的。因此，这种保守的重复可能促进了个体内多态性染色体变异的保留以及物种之间染色体内的重排——这两个因素先前被假设有助于该属表现出极其广泛的生态适应。