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The signature of the Cestrum genome suggests an evolutionary response to the loss of (TTTAGGG)n telomeres

机译：Cestrum基因组的特征表明对（TTTAGGG）n 端粒丢失的进化反应

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摘要

The genus Cestrum in the Solanaceae family is unusual in lacking Arabidopsis-type telomeres (TTTAGGG)n, although short interstitial telomeric sequences (ITSs) occur scattered throughout the genome in both orientations. To isolate candidate telomeric sequences in Cestrum we assumed that some of the ITSs were residues of the original telomeres and that they may still be located in the vicinity of present-day telomeres. Three sequence types associated with ITSs were cloned and characterized; these were termed NA3G, BR23 and A/T-rich minisatellite. These high copy number sequences are dispersed across the genome and clustered at a number of chromosomal loci. Their association with ITSs, which can act as recombination hotspots, might indicate past recombination and chromosomal fusion events, processes that may have contributed to the large size of Cestrum chromosomes. The sequences are frequently arranged as NA3G-ITS-BR23 blocks embedded in an A/T-rich minisatellite array. The A/T-rich minisatellite is of particular interest because the consensus 5′-T4–5AGCAG-3′ might be a derivative of “typical” eukaryotic telomeric sequence motifs. The sequence is abundant at the end of some chromosomes in C. parqui and is found not only in Cestrum but also in the closely related genera Sessea and Vestia, which also lack Arabidopsis-type telomeric sequences. However, the sequence is absent from the Solanaceae genera investigated that are outside the group, including the closely related genus Streptosolen, which all have the Arabidopsis-type telomere. The data indicate that the A/T rich minisatellite might have evolved in response to the loss of Arabidopsis-type telomeres.
机译：茄科植物中的Cestrum属植物虽然缺乏拟南芥型端粒（TTTAGGG）n，却是不寻常的，尽管短的间质端粒序列（ITS）沿两个方向散布在整个基因组中。为了分离发芽期中的候选端粒序列，我们假设某些ITS是原始端粒的残基，并且它们可能仍位于当今的端粒附近。克隆并鉴定了与ITS相关的三种序列类型。这些被称为NA3G，BR23和富含A / T的微型卫星。这些高拷贝数序列分散在整个基因组中，并聚集在许多染色体基因座上。它们与可能作为重组热点的ITS的关联可能表明过去的重组和染色体融合事件，这些过程可能导致了大的Cestrum染色体。这些序列通常以嵌入A / T丰富迷你卫星阵列中的NA3G-ITS-BR23块的形式排列。富含A / T的小卫星特别令人感兴趣，因为共有的5'-T4-5 AGCAG-3'可能是“典型”真核端粒序列基序的衍生物。该序列在C. parqui的某些染色体末端丰富，不仅存在于Cestrum中，而且存在于紧密相关的Sessea和Vestia属中，后者也缺少拟南芥型端粒序列。但是，该序列以外的茄科属中没有该序列，包括紧密相关的链霉菌属，它们都具有拟南芥型端粒。数据表明，富含A / T的小卫星可能是由于拟南芥型端粒的丢失而进化的。

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  • 来源
    《Chromosoma》 |2003年第4期|164-172|共9页
  • 作者

    Eva Sýkorová; K. Yoong Lim; Jiri Fajkus; Andrew R. Leitch;

  • 作者单位

    School of Biological Sciences Queen Mary University of LondonInstitute of Biophysics Czech Academy of Sciences and Masaryk University of Brno;

    School of Biological Sciences Queen Mary University of London;

    Institute of Biophysics Czech Academy of Sciences and Masaryk University of Brno;

    School of Biological Sciences Queen Mary University of London;

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