Originally published as Genetics Published Articles Ahead of Print on June 11, 2007.

Genetics, Vol. 176, 2561-2576, August 2007, Copyright © 2007
doi:10.1534/genetics.106.067686

New Candidate Genes for Sex-Comb Divergence Between Drosophila mauritiana and Drosophila simulans

* Genetics Graduate Group, University of California, Davis, California 95616, {ddagger} Center for Population Biology, Section of Evolution and Ecology, University of California, Davis, California 95616 and {dagger} Center for Genetics and Development, University of California, Davis, California 95616

1 Corresponding author: EVE, 2310 Storer Hall, University of California, Davis, CA 95616.
E-mail: rmgraze{at}ucdavis.edu

A large-effect QTL for divergence in sex-comb tooth number between Drosophila simulans and D. mauritiana was previously mapped to 73A–84AB. Here we identify genes that are likely contributors to this divergence. We first improved the mapping resolution in the 73A–84AB region using 12 introgression lines and 62 recombinant nearly isogenic lines. To further narrow the list of candidate genes, we assayed leg-specific expression and identified genes with transcript-level evolution consistent with a potential role in sex-comb divergence. Sex combs are formed on the prothoracic (front) legs, but not on the mesothoracic (middle) legs of Drosophila males. We extracted RNA from the prothoracic and mesothoracic pupal legs of two species to determine which of the genes expressed differently between leg types were also divergent for gene expression. Two good functional candidate genes, Scr and dsx, are located in one of our fine-scale QTL regions. In addition, three previously uncharacterized genes (CG15186, CG2016, and CG2791) emerged as new candidates. These genes are located in regions strongly associated with sex-comb tooth number differences and are expressed differently between leg tissues and between species. Further supporting the potential involvement of these genes in sex-comb divergence, we found a significant difference in sex-comb tooth number between co-isogenic D. melanogaster lines with and without P-element insertions at CG2791.




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A. Ahuja and R. S. Singh
Variation and Evolution of Male Sex Combs in Drosophila: Nature of Selection Response and Theories of Genetic Variation for Sexual Traits
Genetics, May 1, 2008; 179(1): 503 - 509.
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