Adaptive evolution of newly emerged micro-RNA genes in Drosophila |
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Authors: | Lu Jian Fu Yonggui Kumar Supriya Shen Yang Zeng Kai Xu Anlong Carthew Richard Wu Chung-I |
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Institution: | * Department of Ecology and Evolution, University of Chicago
State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen (Zhongshan) University, Guangzhou, People's Republic of China
Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University |
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Abstract: | How often micro-RNA (miRNA) genes emerged and how fast theyevolved soon after their emergence are some of the central questionsin the evolution of miRNAs. Because most known miRNA genes areancient and highly conserved, these questions can be best answeredby identifying newly emerged miRNA genes. Among the 78 miRNAgenes in Drosophila reported before 2007, only 5 are confirmedto be newly emerged in the genus (although many more can befound in the newly reported data set; e.g., Ruby et al. 2007;Stark et al. 2007; Lu et al. 2008). These new miRNA genes haveundergone numerous changes, even in the normally invariant maturesequences. Four of them (the miR-310/311/312/313 cluster, denotedmiR-310s) were duplicated from other conserved miRNA genes.The fifth one (miR-303) appears to be a very young gene, originatingde novo from a non-miRNA sequence recently. We sequenced these5 miRNA genes and their neighboring regions from a worldwidecollection of Drosophila melanogaster lines. The levels of divergenceand polymorphism in these miRNA genes, vis-à-vis thoseof the neighboring DNA sequences, suggest that these 5 genesare evolving adaptively. Furthermore, the polymorphism patternof miR-310s in D. melanogaster is indicative of hitchhikingunder positive selection. Thus, a large number of adaptive changesover a long period of time may be essential for the evolutionof newly emerged miRNA genes. |
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Keywords: | adaptive evolution micro-RNAs Drosophila new gene |
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