Fossil Rhabdoviral Sequences Integrated into Arthropod Genomes: Ontogeny, Evolution, and Potential Functionality
Fossil Rhabdoviral Sequences Integrated into Arthropod Genomes: Ontogeny, Evolution, and Potential Functionality
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DOI：
10.1093/molbev/msr226
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发表时间：
2012-01-01
影响因子：
10.7
通讯作者：
Weill, Mylene
中科院分区：
文献类型：
--
作者：
Fort, Philippe;Albertini, Aurelie;Weill, Mylene
逆转录因子在许多真核生物基因组中占相当大的比例，被认为是适应性遗传创新的主要驱动力。最近的发现表明，尽管不像逆转录病毒那样通常使用DNA中间体，但单负病毒（即，具有非节段、负义RNA基因组的病毒）可以将基因片段整合到其宿主的基因组中。这一点在博尔纳病毒科和丝状病毒科中得到了证实，它们的序列已被发现整合到许多脊椎动物宿主的种系细胞中。在这里，我们表明，弹状病毒科序列，主要的单负链甲状旁腺病毒家族，已整合到节肢动物物种的基因组。我们确定了185个编码核蛋白、糖蛋白或RNA依赖性RNA聚合酶的整合弹状病毒元件（IRES），它们主要存在于埃及伊蚊和黑腿蜱的基因组中。系统发育分析表明，A.埃及是由多个独立的融合事件演变而来的。由于RNA病毒与其宿主相比具有更高的替换率，因此IRE代表了已灭绝弹状病毒多样性的化石痕迹。此外，还对A.在世界范围内采样的埃及野外蚊子鉴定出了一个整合的聚合酶IRE片段，该片段在数百万年内出现在纯化选择中，这支持了宿主生物学中的功能性作用。结果表明，A.埃及伊蚊在进化过程中经历了弹状病毒的反复感染，积累了许多完整的序列。他们还表明，像逆转录病毒一样，整合的弹状病毒序列可能积极参与宿主的进化。
Retroelements represent a considerable fraction of many eukaryotic genomes and are considered major drives for adaptive genetic innovations. Recent discoveries showed that despite not normally using DNA intermediates like retroviruses do, Mononegaviruses (i.e., viruses with nonsegmented, negative-sense RNA genomes) can integrate gene fragments into the genomes of their hosts. This was shown for Bornaviridae and Filoviridae, the sequences of which have been found integrated into the germ line cells of many vertebrate hosts. Here, we show that Rhabdoviridae sequences, the major Mononegavirales family, have integrated only into the genomes of arthropod species. We identified 185 integrated rhabdoviral elements (IREs) coding for nucleoproteins, glycoproteins, or RNA-dependent RNA polymerases; they were mostly found in the genomes of the mosquito Aedes aegypti and the blacklegged tick Ixodes scapularis. Phylogenetic analyses showed that most IREs in A. aegypti derived from multiple independent integration events. Since RNA viruses are submitted to much higher substitution rates as compared with their hosts, IREs thus represent fossil traces of the diversity of extinct Rhabdoviruses. Furthermore, analyses of orthologous IREs in A. aegypti field mosquitoes sampled worldwide identified an integrated polymerase IRE fragment that appeared under purifying selection within several million years, which supports a functional role in the host's biology. These results show that A. aegypti was subjected to repeated Rhabdovirus infectious episodes during its evolution history, which led to the accumulation of many integrated sequences. They also suggest that like retroviruses, integrated rhabdoviral sequences may participate actively in the evolution of their hosts.