Rampant Horizontal Transfer of SPIN Transposons in Squamate Reptiles
Rampant Horizontal Transfer of SPIN Transposons in Squamate Reptiles
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DOI：
10.1093/molbev/msr181
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发表时间：
2012-02-01
影响因子：
10.7
通讯作者：
Feschotte, Cedric
中科院分区：
文献类型：
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作者：
Gilbert, Clement;Hernandez, Sharon S.;Feschotte, Cedric
转座因子（TE）在基因组中高度丰富，并具有移动性，这两种特性使它们特别容易在生物体之间水平转移。虽然TE的水平转移（HT）的影响在原核生物中得到了很好的认识，但这种现象的频率及其对真核生物基因组进化的贡献仍然不太清楚。在这里，我们提供的证据表明，一种称为SPIN的DNA转座子已经在17种爬行动物的基因组中定居，这些爬行动物几乎代表了每一个主要的有鳞动物谱系，包括14个蜥蜴、蛇和两栖动物家族。狭缝印迹分析表明，在大多数这些物种中，SPIN扩增到高拷贝数，范围从每个单倍体基因组2，000 - 28，000个拷贝。相比之下，我们无法检测到任何海龟（7个科的7个物种）和鳄鱼（4个物种）中存在的自旋。考虑到所研究的家族的深进化分歧（大多数分歧> 100 My），来自不同有鳞动物家族的物种的SPIN序列之间的遗传距离一直很低（平均= 0.1）。此外，这些距离低于两个已知在脊椎动物中强功能约束下进化的基因（RAG 1，平均值= 0.24和C-mos，平均值= 0.27）的家族间距离。这些数据，结合系统发育分析，表明SPIN在有鳞目动物中的广泛分布是至少13个独立的HT事件的结果。分子年代测定和古生物地理学数据表明，这些转移发生在过去的50年中，至少在三个不同的大陆（北美，南美和非洲）。总之，这些结果的三倍的四足动物之间的已知的SPIN转移事件的数量，提供了证据，以前假设的跨洋运动的SPIN转座子在新生代，并进一步强调了HT在脊椎动物基因组的进化中的作用。
Transposable elements (TEs) are highly abundant in the genome and capable of mobility, two properties that make them particularly prone to transfer horizontally between organisms. Although the impact of horizontal transfer (HT) of TEs is well recognized in prokaryotes, the frequency of this phenomenon and its contribution to genome evolution in eukaryotes remain poorly appreciated. Here, we provide evidence that a DNA transposon called SPIN has colonized the genome of 17 species of reptiles representing nearly every major lineage of squamates, including 14 families of lizards, snakes, and amphisbaenians. Slot blot analyses indicate that SPIN has amplified to high copy numbers in most of these species, ranging from 2,000-28,000 copies per haploid genome. In contrast, we could not detect the presence of SPIN in any of the turtles (seven species from seven families) and crocodiles (four species) examined. Genetic distances between SPIN sequences from species belonging to different squamate families are consistently very low (average = 0.1), considering the deep evolutionary divergence of the families investigated (most are > 100 My diverged). Furthermore, these distances fall below interfamilial distances calculated for two genes known to have evolved under strong functional constraint in vertebrates (RAG1, average = 0.24 and C-mos, average = 0.27). These data, combined with phylogenetic analyses, indicate that the widespread distribution of SPIN among squamates is the result of at least 13 independent events of HTs. Molecular dating and paleobiogeographical data suggest that these transfers took place during the last 50 My on at least three different continents (North America, South America and, Africa). Together, these results triple the number of known SPIN transfer events among tetrapods, provide evidence for a previously hypothesized transoceanic movement of SPIN transposons during the Cenozoic, and further underscore the role of HT in the evolution of vertebrate genomes.