Duplication and diversification of Dipteran Argonaute genes, and the evolutionary divergence of Piwi and Aubergine

Samuel H Lewis, Heli Salmela, Darren Obbard

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Genetic studies of Drosophila melanogaster have provided a paradigm for RNAi in arthropods, in which the miRNA 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 analyse 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 million years ago), independent origins of multiple Piwi-family genes in Aedes mosquitoes (less than 25mya), 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 paralogues 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.

Original languageEnglish
JournalGenome Biology and Evolution
Early online date11 Feb 2016
DOIs
Publication statusPublished - 1 Mar 2016

Keywords / Materials (for Non-textual outputs)

  • RNAi
  • Argonaute
  • Piwi
  • gene duplication
  • Diptera

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