Repeated Duplication of Argonaute2 Is Associated with Strong Selection and Testis Specialization in Drosophila

Samuel H LewisDarren J Obbard


Argonaute2 (Ago2) is a rapidly evolving nuclease in the Drosophila melanogaster RNA interference (RNAi) pathway that targets viruses and transposable elements in somatic tissues. Here we reconstruct the history of Ago2 duplications across the D. obscura group and use patterns of gene expression to infer new functional specialization. We show that some duplications are old, shared by the entire species group, and that losses may be common, including previously undetected losses in the lineage leading to D. pseudoobscura We find that while the original (syntenic) gene copy has generally retained the ancestral ubiquitous expression pattern, most of the novel Ago2 paralogs have independently specialized to testis-specific expression. Using population genetic analyses, we show that most testis-specific paralogs have significantly lower genetic diversity than the genome-wide average. This suggests recent positive selection in three different species, and model-based analyses provide strong evidence of recent hard selective sweeps in or near four of the six D. pseudoobscura Ago2 paralogs. We speculate that the repeated evolution of testis specificity in obscura group Ago2 genes, combined with their dynamic turnover and strong signatur...Continue Reading


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Related Concepts

Meiotic Cell Cycle
Biochemical Pathway
Benign Neoplasm of Testis
AGO2 gene
PIWI Subfamily of Argonaute Proteins
EIF2C2 protein, human
Neoplasm of Uncertain or Unknown Behavior of Testis

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