Journal Article

Hyperexpression of the X Chromosome in Both Sexes Results in Extensive Female Bias of X-Linked Genes in the Flour Beetle

Eldon G. Prince, Donna Kirkland and Jeffery P. Demuth

in Genome Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 2, issue , pages 336-346
Published in print January 2010 |
Published online May 2010 | e-ISSN: 1759-6653 | DOI:

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  • Bioinformatics and Computational Biology
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A genome's ability to produce two separate sexually dimorphic phenotypes is an intriguing biological mystery. Microarray-based studies of a handful of model systems suggest that much of the mystery can be explained by sex-biased gene expression evolved in response to sexually antagonistic selection. We present the first whole-genome study of sex-biased expression in the red flour beetle, Tribolium castaneum. Tribolium is a model for the largest eukaryotic order, Coleoptera, and we show that in whole-body adults, ∼20% of the transcriptome is differentially regulated between the sexes. Among T. castaneum, Drosophila melanogaster, and Anopheles gambiae, we identify 416 1:1:1 orthologs with conserved sex-biased expression. Overrepresented functional categories among sex-biased genes are primarily those involved in gamete production and development. The genomic distribution of sex-biased genes in T. castaneum is distinctly nonrandom, with the strongest deficit of male-biased genes on the X chromosome (9 of 793) of any species studied to date. Tribolium also shows a significant enrichment of X-linked female-biased genes (408 of 793). Our analyses suggest that the extensive female bias of Tribolium X chromosome gene expression is due to hyperexpression of X-linked genes in both males and females. We propose that the overexpression of X chromosomes in females is an evolutionary side effect of the need to dosage compensate in males and that mechanisms to reduce female X chromosome gene expression to autosomal levels are sufficient but imperfect.

Keywords: dosage compensation; sex chromosomes; microarrays; Tribolium

Journal Article.  6562 words.  Illustrated.

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

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