W chromosome expression responds to female-specific selection

Proc Natl Acad Sci U S A. 2012 May 22;109(21):8207-11. doi: 10.1073/pnas.1202721109. Epub 2012 May 8.


The W chromosome is predicted to be subject to strong female-specific selection stemming from its female-limited inheritance and therefore should play an important role in female fitness traits. However, the overall importance of directional selection in shaping the W chromosome is unknown because of the powerful degradative forces that act to decay the nonrecombining sections of the genome. Here we greatly expand the number of known W-linked genes and assess the expression of the W chromosome after >100 generations of different female-specific selection regimens in different breeds of chicken and in the wild ancestor, the Red Jungle Fowl. Our results indicate that female-specific selection has a significant effect on W chromosome gene-expression patterns, with a strong convergent pattern of up-regulation associated with increased female-specific selection. Many of the transcriptional changes in the female-selected breeds are the product of positive selection, suggesting that selection is an important force in shaping the evolution of gene expression on the W chromosome, a finding consistent with both the importance of the W chromosome in female fertility and the haploid nature of the W. Taken together, these data provide evidence for the importance of the sex-limited chromosome in a female heterogametic species and show that sex-specific selection can act to preserve sex-limited chromosomes from degrading forces.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Husbandry / methods*
  • Animals
  • Chick Embryo
  • Chickens / genetics*
  • Evolution, Molecular*
  • Female
  • Male
  • Oviposition / genetics
  • Polymorphism, Genetic / genetics
  • Sex Chromosomes / genetics*
  • Sex Preselection*
  • Species Specificity