Journal Article

A Complex Suite of Forces Drives Gene Traffic from <i>Drosophila</i> X Chromosomes

Richard P. Meisel, Mira V. Han and Matthew W. Hahn

in Genome Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 1, issue , pages 176-188
Published in print January 2009 |
Published online July 2009 | e-ISSN: 1759-6653 | DOI: http://dx.doi.org/10.1093/gbe/evp018

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Theoretical studies predict X chromosomes and autosomes should be under different selection pressures, and there should therefore be differences in sex-specific and sexually antagonistic gene content between the X and the autosomes. Previous analyses have identified an excess of genes duplicated by retrotransposition from the X chromosome in Drosophila melanogaster. A number of hypotheses may explain this pattern, including mutational bias, escape from X-inactivation during spermatogenesis, and the movement of male-favored (sexually antagonistic) genes from a chromosome that is predominantly carried by females. To distinguish among these processes and to examine the generality of these patterns, we identified duplicated genes in nine sequenced Drosophila genomes. We find that, as in D. melanogaster, there is an excess of genes duplicated from the X chromosome across the genus Drosophila. This excess duplication is due almost completely to genes duplicated by retrotransposition, with little to no excess from the X among genes duplicated via DNA intermediates. The only exception to this pattern appears within the burst of duplication that followed the creation of the Drosophila pseudoobscura neo-X chromosome. Additionally, we examined genes relocated among chromosomal arms (i.e., genes duplicated to new locations coupled with the loss of the copy in the ancestral locus) and found an excess of genes relocated off the ancestral X and neo-X chromosomes. Interestingly, many of the same genes were duplicated or relocated from the independently derived neo-X chromosomes of D. pseudoobscura and Drosophila willistoni, suggesting that natural selection favors the traffic of genes from X chromosomes. Overall, we find that the forces driving gene duplication from X chromosomes are dependent on the lineage in question, the molecular mechanism of duplication considered, the preservation of the ancestral copy, and the age of the X chromosome.

Keywords: gene duplication; retrotransposition; sex chromosomes; neo-X chromosomes; X-inactivation

Journal Article.  9183 words.  Illustrated.

Subjects: Bioinformatics and Computational Biology ; Evolutionary Biology ; Genetics and Genomics

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