Non-allelic gene conversion enables rapid evolutionary change at multiple regulatory sites encoded by transposable elements
Abstract
Transposable elements (TEs) allow rewiring of regulatory networks, and the recent amplification of the ISX-element dispersed 77 functional but suboptimal binding-sites for the dosage-compensation-complex to a newly-formed X-chromosome in Drosophila. Here we identify two linked refining-mutations within ISX that interact epistatically to increase binding affinity to the dosage-compensation-complex. Selection has increased the frequency of this derived haplotype in the population, which is fixed at 30% of ISX-insertions and polymorphic among another 41%. Sharing of this haplotype indicates that high levels of gene-conversion among ISX-elements allow them to 'crowd-source' refining-mutations, and a refining-mutation that occurs at any single ISX-element can spread in two dimensions: horizontally across insertion sites by non-allelic gene-conversion, and vertically through the population by natural selection. These describes a novel route how fully functional regulatory elements can arise rapidly from TEs and implicate non-allelic gene-conversion as having an important role in accelerating the evolutionary fine-tuning of regulatory networks.
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© 2015, Ellison & Bachtrog
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