title: W chromosome expression responds to female-specific selection.
abstract: 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.
authors.affiliation: Department of Zoology, Edward Grey Institute,  University of Oxford, Oxford OX1 3PS,  United Kingdom.
authors.forename: Hooman K
authors.initials: HK
authors.lastname: Moghadam
authors.forename: Marie A
authors.initials: MA
authors.lastname: Pointer
authors.forename: Alison E
authors.initials: AE
authors.lastname: Wright
authors.forename: Sofia
authors.initials: S
authors.lastname: Berlin
authors.forename: Judith E
authors.initials: JE
authors.lastname: Mank
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics*; D019143:Evolution, Molecular; D005260:Female; D008297:Male; D010058:Oviposition / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics; D012730:Sex Chromosomes / Q000235:genetics*; D012743:Sex Preselection; D013045:Species Specificity