Satellite repeats are major sequence constituents of centromeres in many plant and animal species. Within a species, a single family of satellite sequences typically occupies centromeres of all chromosomes and is absent from other parts of the genome. Due to their common origin, sequence similarities exist among the centromere-specific satellites in related species. Here, we report a remarkably different pattern of centromere evolution in the plant tribe Fabeae, which includes genera Pisum, Lathyrus, Vicia, and Lens. By immunoprecipitation of centromeric chromatin with CENH3 antibodies, we identified and characterized a large and diverse set of 64 families of centromeric satellites in 14 species. These families differed in their nucleotide sequence, monomer length (33–2,979 bp), and abundance in individual species. Most families were species-specific, and most species possessed multiple (2–12) satellites in their centromeres. Some of the repeats that were shared by several species exhibited promiscuous patterns of centromere association, being located within CENH3 chromatin in some species, but apart from the centromeres in others. Moreover, FISH experiments revealed that the same family could assume centromeric and noncentromeric positions even within a single species. Taken together, these findings suggest that Fabeae centromeres are not shaped by the coevolution of a single centromeric satellite with its interacting CENH3 proteins, as proposed by the centromere drive model. This conclusion is also supported by the absence of pervasive adaptive evolution of CENH3 sequences retrieved from Fabeae species.

中文翻译：

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豆科豆科着丝粒卫星的非凡序列多样性和混杂性。


卫星重复是许多植物和动物物种着丝粒的主要序列组成部分。在一个物种内，卫星序列的单个家族通常占据所有染色体的着丝粒，并且在基因组的其他部分中不存在。由于它们的共同起源，相关物种的着丝粒特异性卫星之间存在序列相似性。在这里，我们报告了豆科植物族（包括豌豆属、山黧豆属、蚕豆属和透镜属）中着丝粒进化的显着不同模式。通过使用 CENH3 抗体对着丝粒染色质进行免疫沉淀，我们鉴定并表征了 14 个物种的 64 个着丝粒卫星家族的大量且多样化的特征。这些家族的核苷酸序列、单体长度（33-2,979 bp）和各个物种的丰度有所不同。大多数科都是物种特异性的，并且大多数物种在着丝粒中拥有多个（2-12）卫星。几个物种共有的一些重复序列表现出着丝粒关联的混杂模式，在某些物种中位于 CENH3 染色质内，但在其他物种中则位于着丝粒之外。此外，FISH 实验表明，即使在单个物种内，同一家族也可以占据着丝粒和非着丝粒位置。总而言之，这些发现表明豆科着丝粒并不是由单个着丝粒卫星与其相互作用的 CENH3 蛋白共同进化形成的，正如着丝粒驱动模型所提出的那样。从豆科物种中检索到的 CENH3 序列缺乏普遍的适应性进化也支持了这一结论。