Telomeres are terminal regions of linear eukaryotic chromosomes that are critical for genome stability and continued cell proliferation. The draft assembly of the papaya genome provides an opportunity to analyze and compare the evolution of telomeric DNA sequence composition and telomere maintenance machinery in this and other organisms of the Brassicales Order, which includes Arabidopsis. Here we investigate telomere size and sequence variation at papaya chromosome ends. As with most other plant species, papaya telomeres consist of TTTAGGG repeats. However, in contrast to members of the closely related Brassicaceae family, telomeres in papaya are ~10-fold longer. Sequence analysis reveals that many centromereproximal telomere repeats in papaya harbor nucleotide substitutions and insertions of Gs and Ts. In contrast, we found very few N-to-C substitutions, and even fewer instances of nucleotide deletion, suggesting that a six-nucleotide telomere repeat is not well tolerated. The papaya genome encodes single-copy sequence homologues of several genes involved in telomere maintenance and chromosome end protection, including the Telomerase Reverse Transcriptase (TERT) and Protection Of Telomeres (POT1). Notably, unlike Arabidopsis, which encodes six Telomere Repeat binding Factor-like (TRFL) proteins that bind double-stranded telomere DNA, papaya appears to encode only two such proteins. Thus, the more streamlined genome of papaya will provide an excellent resource for comparative and functional analysis of telomeres in plants.

中文翻译：

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Carica papaya 端粒和端粒相关蛋白的分析：对 Brassicales 端粒维持进化的洞察。

端粒是线性真核染色体的末端区域，对基因组稳定性和持续细胞增殖至关重要。木瓜基因组的组装草案提供了一个机会来分析和比较端粒 DNA 序列组成和端粒维持机制在这个和其他芸苔目生物（包括拟南芥）中的进化。在这里，我们研究了木瓜染色体末端的端粒大小和序列变异。与大多数其他植物物种一样，木瓜端粒由 TTTAGGG 重复序列组成。然而，与密切相关的十字花科的成员相比，木瓜中的端粒长约 10 倍。序列分析表明，木瓜中的许多着丝粒近端端粒重复序列包含核苷酸替换以及 Gs 和 Ts 的插入。相比之下，我们发现很少的 N 到 C 替换，甚至更少的核苷酸缺失实例，表明六核苷酸端粒重复不能很好地耐受。木瓜基因组编码涉及端粒维持和染色体末端保护的几个基因的单拷贝序列同源物，包括端粒酶逆转录酶 (TERT) 和端粒保护 (POT1)。值得注意的是，与编码六个端粒重复结合因子样 (TRFL) 蛋白结合双链端粒 DNA 的拟南芥不同，木瓜似乎只编码两个这样的蛋白质。因此，更精简的木瓜基因组将为植物端粒的比较和功能分析提供极好的资源。木瓜基因组编码涉及端粒维持和染色体末端保护的几个基因的单拷贝序列同源物，包括端粒酶逆转录酶 (TERT) 和端粒保护 (POT1)。值得注意的是，与编码六个端粒重复结合因子样 (TRFL) 蛋白结合双链端粒 DNA 的拟南芥不同，木瓜似乎只编码两个这样的蛋白质。因此，更精简的木瓜基因组将为植物端粒的比较和功能分析提供极好的资源。木瓜基因组编码涉及端粒维持和染色体末端保护的几个基因的单拷贝序列同源物，包括端粒酶逆转录酶 (TERT) 和端粒保护 (POT1)。值得注意的是，与编码六个端粒重复结合因子样 (TRFL) 蛋白结合双链端粒 DNA 的拟南芥不同，木瓜似乎只编码两个这样的蛋白质。因此，更精简的木瓜基因组将为植物端粒的比较和功能分析提供极好的资源。木瓜编码六个端粒重复结合因子样 (TRFL) 蛋白，这些蛋白结合双链端粒 DNA，木瓜似乎只编码两个这样的蛋白质。因此，更精简的木瓜基因组将为植物端粒的比较和功能分析提供极好的资源。木瓜编码六个端粒重复结合因子样 (TRFL) 蛋白，这些蛋白结合双链端粒 DNA，木瓜似乎只编码两个这样的蛋白质。因此，更精简的木瓜基因组将为植物端粒的比较和功能分析提供极好的资源。