Maternal expression increases the rate of <Emphasis Type="Italic">bicoid</Emphasis> evolution
by relaxing selective constraint |
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Authors: | Jeffery P Demuth Michael J Wade |
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Institution: | (1) Department of Biology, Indiana University, 1001 East 3rd Street, Bloomington, IN 47405, USA |
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Abstract: | Population genetic theory predicts that maternal effect genes will evolve differently than genes expressed in both sexes because
selection is only half as effective on autosomal genes expressed in one sex but not the other. Here, we use sequences of the
tandem gene duplicates, bicoid (bcd) and zerknüllt (zen), to test the prediction that, with similar coefficients of purifying selection, a maternal effect gene evolves more rapidly
than a zygotic gene because of this reduction in selective constraint. We find that the maternal effect gene, bcd, is evolving more rapidly than zygotically expressed, zen, providing the first direct confirmation of this prediction of maternal effect theory from molecular evidence. Our results
extend current explanations for the accelerated rate of bcd evolution by providing an evolutionary mechanism, relaxed selective constraint, that allows bcd the evolutionary flexibility to escape the typical functional constraints of early developmental genes. We discuss general
implications of our findings for the role of maternal effect genes in early developmental patterning. |
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Keywords: | Maternal effect genes bicoid zerknüllt Hox genes Developmental hourglass Molecular evolution Selective constraint |
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