Tubío Jose Manuel C, Costas Javier C, Naveira Horacio F
Departamento de Xenética, Facultade de Bioloxía, Universidade de Santiago de Compostela, Spain.
Gene. 2004 Apr 14;330:123-31. doi: 10.1016/j.gene.2004.01.012.
So far, only a few retrovirus-like transposable elements (TEs) have been reported in Anopheles mosquitoes, although a large fraction of their genomes is made up of these middle repetitive sequences. By screening the A. gambiae genome databases, we have found 10 element families belonging to the mdg1 lineage of the Ty3/gypsy group of long terminal repeat (LTR) retrotransposons. These Anopheles families constitute a sister clade of the Drosophila representatives of this same lineage. According to the phylogenetic reconstruction of their open reading frame (ORF)2 enzymatic domains, the analysis of patterns of nucleotide substitution therein, and the estimation of the age of particular insertions, all these elements must have been active until quite recently, and some of them must be very young. On the other hand, the fact that all these element families are primarily composed of fragmentary copies (mostly solos) or full-length copies with inactivating mutations indicates that their turnover rate has been probably very low. Finally, incongruent phylogenies obtained from different regions of the elements strongly suggest that recombination has played a significant role in their evolutionary history.
到目前为止，尽管按蚊基因组的很大一部分由这些中等重复序列组成，但在按蚊中仅报道了少数几种逆转录病毒样转座元件（TEs）。通过筛选冈比亚按蚊基因组数据库，我们发现了10个属于长末端重复（LTR）逆转录转座子Ty3/gypsy组mdg1谱系的元件家族。这些按蚊家族构成了同一谱系果蝇代表的姐妹进化枝。根据其开放阅读框（ORF）2酶结构域的系统发育重建、其中核苷酸替代模式的分析以及特定插入片段年龄的估计，所有这些元件直到最近都必定是活跃的，而且其中一些必定非常年轻。另一方面，所有这些元件家族主要由片段化拷贝（大多为单独拷贝）或具有失活突变的全长拷贝组成，这一事实表明它们的更新率可能非常低。最后，从元件不同区域获得的不一致系统发育强烈表明重组在它们的进化历史中发挥了重要作用。
