Telomeric repeat arrays at the ends of chromosomes are highly dynamic in composition, but their repetitive nature and technological limitations have made it difficult to assess their true variation in genome diversity surveys. We have comprehensively characterized the sequence variation immediately adjacent to the canonical telomeric repeat arrays at the very ends of chromosomes in 74 genetically diverse Arabidopsis thaliana accessions. We first describe several types of distinct telomeric repeat units and then identify evolutionary processes such as local homogenization and higher-order repeat formation that shape diversity of chromosome ends. By comparing largely isogenic samples, we also determine repeat number variation of the degenerate and variant telomeric repeat array at both the germline and somatic levels. Finally, our analysis of haplotype structure uncovers chromosome end-specific patterns in the distribution of variant telomeric repeats, and their linkage to the more proximal non-coding region. Our findings illustrate the spectrum of telomeric repeat variation at multiple levels in A. thaliana—in germline and soma, across all chromosome ends, and across genetic groups—thereby expanding our knowledge of the evolution of chromosome ends.

中文翻译：

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拟南芥端粒重复多样性图谱


染色体末端的端粒重复序列在组成上是高度动态的，但它们的重复性质和技术限制使得在基因组多样性调查中很难评估它们的真实变异。我们全面表征了 74 个遗传多样性拟南芥种质中染色体最末端紧邻典型端粒重复序列的序列变异。我们首先描述了几种不同类型的端粒重复单元，然后确定了进化过程，例如塑造染色体末端多样性的局部同质化和高阶重复形成。通过比较大部分同基因样本，我们还确定了简并和变异端粒重复阵列在种系和体细胞水平上的重复次数变化。最后，我们对单倍型结构的分析揭示了变异端粒重复分布中的染色体末端特异性模式，以及它们与更近端非编码区的联系。我们的研究结果说明了拟南芥中多个水平的端粒重复变异谱——种系和体细胞、所有染色体末端以及遗传群体——从而扩展了我们对染色体末端进化的认识。