title: Complex evolutionary trajectories of sex chromosomes across bird taxa.
abstract: Sex-specific chromosomes, like the W of most female birds and the Y of male mammals, usually have lost most genes owing to a lack of recombination. We analyze newly available genomes of 17 bird species representing the avian phylogenetic range, and find that more than half of them do not have as fully degenerated W chromosomes as that of chicken. We show that avian sex chromosomes harbor tremendous diversity among species in their composition of pseudoautosomal regions and degree of Z/W differentiation. Punctuated events of shared or lineage-specific recombination suppression have produced a gradient of "evolutionary strata" along the Z chromosome, which initiates from the putative avian sex-determining gene DMRT1 and ends at the pseudoautosomal region. W-linked genes are subject to ongoing functional decay after recombination was suppressed, and the tempo of degeneration slows down in older strata. Overall, we unveil a complex history of avian sex chromosome evolution.
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA94720, USA. zhouqi@berkeley.edu zhanggj@genomics.org.cn.
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: China National Genebank, BGI-Shenzhen, Shenzhen, 518083. China.
authors.forename: Jilin
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Department of Integrative Biology, University of California, Berkeley, CA94720, USA.
authors.forename: Doris
authors.initials: D
authors.lastname: Bachtrog
authors.affiliation: China National Genebank, BGI-Shenzhen, Shenzhen, 518083. China.
authors.forename: Na
authors.initials: N
authors.lastname: An
authors.affiliation: China National Genebank, BGI-Shenzhen, Shenzhen, 518083. China.
authors.forename: Quanfei
authors.initials: Q
authors.lastname: Huang
authors.affiliation: Department of Neurobiology, Howard Hughes Medical Institute, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Erich D
authors.initials: ED
authors.lastname: Jarvis
authors.affiliation: Centre for GeoGenetics, Natural History Museum of Denmark, University of Copenhagen, Øster Voldgade 5-7, 1350 Copenhagen, Denmark. Trace and Environmental DNA laboratory, Department of Environment and Agriculture, Curtin University, Perth, Western Australia 6102, Australia.
authors.forename: M Thomas P
authors.initials: MT
authors.lastname: Gilbert
authors.affiliation: China National Genebank, BGI-Shenzhen, Shenzhen, 518083. China. Centre for Social Evolution, Department of Biology, Universitetsparken 15, University of Copenhagen, DK-2100 Copenhagen, Denmark. zhouqi@berkeley.edu zhanggj@genomics.org.cn.
authors.forename: Guojie
authors.initials: G
authors.lastname: Zhang
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000235:genetics; D005075:Biological Evolution; D001717:Birds / Q000145:classification / Q000235:genetics*; D002645:Chickens / Q000235:genetics; D007446:Chromosome Inversion; D002874:Chromosome Mapping; D019143:Evolution, Molecular; D005260:Female; D008297:Male; D010802:Phylogeny; D011995:Recombination, Genetic; D012730:Sex Chromosomes / Q000235:genetics*; D013045:Species Specificity; D020310:Struthioniformes / Q000235:genetics; D026801:Synteny; D014157:Transcription Factors / Q000235:genetics
chemical_list: D030161:Avian Proteins; C110547:DMRT1 protein; D014157:Transcription Factors