Genomic gigantism: DNA loss is slow in mountain grasshoppers
Genomic gigantism: DNA loss is slow in mountain grasshoppers
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DOI：
10.1093/oxfordjournals.molbev.a003798
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发表时间：
2001-02-01
影响因子：
10.7
通讯作者：
Hewitt, GM
中科院分区：
文献类型：
--
作者：
Bensasson, D;Petrov, DA;Hewitt, GM
几项研究表明，动物的DNA丢失与基因组大小呈负相关。这些研究包括果蝇和蟋蟀Laupala之间的比较，但还没有对拥有非常大基因组的昆虫的DNA丢失进行评估。褐斑潜蝇的基因组是果蝇的100多倍，是月桂的10倍。我们利用58个线粒体起源的近缘核假基因，研究了胡枝子菜和意大利人的插入、缺失和点替换的特征。在动物中，这些假基因是“到达即死”的；它们在许多不同的真核生物中大量存在，它们的线粒体起源简化了核假基因谱系中积累的点替换的鉴定。在所研究的643个碱基的假基因序列中，似乎有一个单核苷酸重复序列，它是插入或缺失(INDELs)的强烈热点。由于其他昆虫物种的数据不包含这样一个不寻常的区域，因此热点被排除在物种比较之外。在被研究的蝗虫中，相对于点替换的DNA丢失率似乎明显低于果蝇或萝卜拉。这表明，基因组大小和DNA丢失率之间的负相关可以扩展到具有大型或巨型基因组的昆虫之间的比较(即Laupala和Podisma)。DNA丢失率低表明，在蝗虫中，点突变的积累比它们通过内切积累的丢失更能掩盖古老的假基因，而果蝇的情况正好相反。造成蝗虫、蟋蟀和果蝇DNA损失率差异的主要因素似乎是缺失大小。在Podisma和Italopodisma中，较大的删除相对较少。
Several studies have shown DNA loss to be inversely correlated with genome size in animals. These studies include a comparison between Drosophila and the cricket, Laupala, but there has been no assessment of DNA loss in insects with very large genomes. Podisma pedestris, the brown mountain grasshopper, has a genome over 100 times as large as that of Drosophila and 10 times as large as that of Laupala. We used 58 paralogous nuclear pseudogenes of mitochondrial origin to study the characteristics of insertion, deletion, and point substitution in P. pedestris and Italopodisma. In animals, these pseudogenes are "dead on arrival"; they are abundant in many different eukaryotes, and their mitochondrial origin simplifies the identification of point substitutions accumulated in nuclear pseudogene lineages. There appears to be a mononucleotide repeat within the 643-bp pseudogene sequence studied that acts as a strong hot spot for insertions or deletions (indels). Because the data for other insect species did not contain such an unusual region, hot spots were excluded from species comparisons. The rate of DNA loss relative to point substitution appears to be considerably and significantly lower in the grasshoppers studied than in Drosophila or Laupala. This suggests that the inverse correlation between genome size and the rate of DNA loss can be extended to comparisons between insects with large or gigantic genomes (i.e., Laupala and Podisma). The low rate of DNA loss implies that in grasshoppers, the accumulation of point mutations is a more potent force for obscuring ancient pseudogenes than their loss through indel accumulation, whereas the reverse is true for Drosophila. The main factor contributing to the difference in the rates of DNA loss estimated for grasshoppers, crickets, and Drosophila appears to be deletion size. Large deletions are relatively rare in Podisma and Italopodisma.