Long-term inheritance of the 28S rDNA-specific retrotransposon R2
Long-term inheritance of the 28S rDNA-specific retrotransposon R2
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DOI：
10.1093/molbev/msi210
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发表时间：
2005-11-01
影响因子：
10.7
通讯作者：
Fujiwara, H
中科院分区：
文献类型：
--
作者：
Kojima, KK;Fujiwara, H
R2 是一种非长末端重复 (LTR) 反转录转座子，可特异性插入 28S rDNA。 R2 已在多种节肢动物和三种脊索动物中被发现。 R2在动物体内的分布可能更为广泛，其起源可能可以追溯到早期的动物进化。在这项研究中，我们利用简并聚合酶链式反应方法鉴定了青鳉鱼、白云山鲦鱼、里维斯龟、盲鳗、海百合和一些节肢动物物种中的 R2 元素。我们还从血吸虫曼氏血吸虫的公共基因组序列数据库中鉴定了两个 R2 元件。两个血吸虫 R2 元件之一的 N 末端有两个锌指基序；这与其他已知的 R2 元件不同，后者具有一个或三个锌指基序。系统发育分析表明，R2的整个系统发育可分为11个部分（亚支），其中局部R2的系统发育与相应的宿主系统发育是一致的。分歧与年龄分析表明，没有可靠的证据证明 R2 水平转移，但支持 R2 在后口动物和原口动物分化之前就已经垂直转移的主张。 R2 系统发育与其宿主的系统发育之间看似不一致是由于旁系同源谱系的存在。 N端锌指基序的数量与R2的深层系统发育一致，表明R2的共同祖先在N端有3个锌指基序。这项研究揭示了 R2 的长期垂直遗传和序列特异性的古老起源，这两者似乎适用于其他一些非 LTR 反转录转座子。
R2 is a non-long-terminal-repeat (LTR) retrotransposon that inserts specifically into 28S rDNA. R2 has been identified in many species of arthropods and three species of chordates. R2 may be even more widely distributed in animals, and its origin may be traceable to early animal evolution. In this study, we identified R2 elements in medaka fish, White Cloud Mountain minnow, Reeves' turtle, hagfish, sea lilies, and some arthropod species, using degenerate polymerase chain reaction methods. We also identified two R2 elements from the public genomic sequence database of the bloodfluke Schistosoma mansoni. One of the two bloodfluke R2 elements has two zinc-finger motifs at the N-terminus; this differs from other known R2 elements, which have one or three zinc-finger motifs. Phylogenetic analysis revealed that the whole phylogeny of R2 can be divided into 11 parts (subclades), in which the local R2 phylogeny and the corresponding host phylogeny are consistent. Divergence-versus-age analysis revealed that there is no reliable evidence for the horizontal transfer of R2 but supports the proposition that R2 has been vertically transferred since before the divergence of the deuterostomes and protostomes. The seeming inconsistency between the R2 phylogeny and the phylogeny of their hosts is due to the existence of paralogous lineages. The number of N-terminal zinc-finger motifs is consistent with the deep phylogeny of R2 and indicates that the common ancestor of R2 had three zinc-finger motifs at the N-terminus. This study revealed the long-term vertical inheritance and the ancient origin of sequence specificity of R2, both of which seem applicable to some other non-LTR retrotransposons.