MBE Advance Access originally published online on August 21, 2006
Molecular Biology and Evolution 2006 23(11):2203-2213; doi:10.1093/molbev/msl094
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Research Articles |
Intron Length Evolution in Drosophila
Department of Molecular Biology and Genetics, Cornell University
E-mail: dvnp{at}mail.rochester.edu.
I present data on the evolution of intron lengths among 3 closely related Drosophila species, D. melanogaster, Drosophila simulans, and Drosophila yakuba. Using D. yakuba as an outgroup, I mapped insertion and deletion mutations in 148 introns (spanning
30 kb) to the D. melanogaster and D. simulans lineages. Intron length evolution in the 2 sister species has been different: in D. melanogaster, X-linked introns have increased slightly in size, whereas autosomal ones have decreased slightly in size; in D. simulans, both X-linked and autosomal introns have decreased in size. To understand the possible evolutionary causes of these lineage- and chromosome-specific patterns of intron evolution, I studied insertiondeletion (indel) polymorphism and divergence in D. melanogaster. Small insertion mutations segregate at elevated frequencies and enjoy elevated probabilities of fixation, particularly on the X chromosome. In contrast, there is no detectable X chromosome effect on fixations in D. simulans. These findings suggest X chromosomespecific selection or biased gene conversiongap repair favoring insertions in D. melanogaster but not in D. simulans. These chromosome- and lineage-specific patterns of indel substitution are not easily explained by existing general population genetic models of intron length evolution. Genomic data from D. melanogaster further suggest that the forces described here affect introns and intergenic regions similarly.
Key Words: Drosophila melanogaster Drosophila simulans intron insertion deletion indel
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