Duplication and Diversification of Dipteran Argonaute Genes, and the Evolutionary Divergence of Piwi and Aubergine.
Duplication and Diversification of Dipteran Argonaute Genes, and the Evolutionary Divergence of Piwi and Aubergine.
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DOI：
10.1093/gbe/evw018
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发表时间：
2016-02-11
影响因子：
3.3
通讯作者：
Obbard DJ
中科院分区：
文献类型：
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作者：
Lewis SH;Salmela H;Obbard DJ
对黑腹果蝇的遗传学研究为节肢动物的RNA干扰(RNAi)提供了一个范例，其中microRNA和抗病毒途径分别由一个ArgAerte(Ago1和Ago2)介导，而种系对转座元件的抑制由三个Piwi亚家族ArgAerte蛋白(Ago3、Aub和Piwi)介导。如果没有合适的进化背景，偏离这一点可以被解释为派生的或特殊的。在这里，我们分析了86个双翅目物种的基因组和转录本中ArgAerte基因的进化，表明拷贝数的变化可以迅速发生，并且在一些RNAi机制中存在恒定的流动。Aub和Piwi的分化(182-156 Ma)，伊蚊中多个Piwi家族基因的独立起源(小于25 Ma)，以及采采蝇Glossina morsitans最近复制的Ago2和Ago3，说明了RNAi途径的不稳定。在每一种情况下，这些基因的组织特异性都发生了变化，这表明功能分化或创新，并与整个ArgAerte基因家族的动态选择压力的作用一致。我们发现不同途径之间的进化速度和基因更新有很大的差异，并且Ago2、Ago3和Piwi/Aub的并列基因在复制后显示出相反的进化速度。这表明阿尔戈斯人经历了频繁的进化扩张，从而促进了功能分化。
Genetic studies of Drosophila melanogaster have provided a paradigm for RNA interference (RNAi) in arthropods, in which the microRNA and antiviral pathways are each mediated by a single Argonaute (Ago1 and Ago2) and germline suppression of transposable elements is mediated by a trio of Piwi-subfamily Argonaute proteins (Ago3, Aub, and Piwi). Without a suitable evolutionary context, deviations from this can be interpreted as derived or idiosyncratic. Here we analyze the evolution of Argonaute genes across the genomes and transcriptomes of 86 Dipteran species, showing that variation in copy number can occur rapidly, and that there is constant flux in some RNAi mechanisms. The lability of the RNAi pathways is illustrated by the divergence of Aub and Piwi (182–156 Ma), independent origins of multiple Piwi-family genes in Aedes mosquitoes (less than 25Ma), and the recent duplications of Ago2 and Ago3 in the tsetse fly Glossina morsitans. In each case the tissue specificity of these genes has altered, suggesting functional divergence or innovation, and consistent with the action of dynamic selection pressures across the Argonaute gene family. We find there are large differences in evolutionary rates and gene turnover between pathways, and that paralogs of Ago2, Ago3, and Piwi/Aub show contrasting rates of evolution after duplication. This suggests that Argonautes undergo frequent evolutionary expansions that facilitate functional divergence.