RT Journal Article
SR Electronic
T1 Dynamic evolutionary history and gene content of sex chromosomes across diverse songbirds
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 454843
DO 10.1101/454843
A1 Luo-hao Xu
A1 Gabriel Auer
A1 Valentina Peona
A1 Alexander Suh
A1 Yuan Deng
A1 Shao-hong Feng
A1 Guo-jie Zhang
A1 Mozes P.K. Blom
A1 Les Christidis
A1 Stefan Prost
A1 Martin Irestedt
A1 Qi Zhou
YR 2018
UL http://biorxiv.org/content/early/2018/10/29/454843.abstract
AB Songbirds have a species number almost equivalent to that of mammals, and are classic models for studying mechanisms of speciation and sexual selection. Sex chromosomes are hotspots of both processes, yet their evolutionary history in songbirds remains unclear. To elucidate that, we characterize female genomes of 11 songbird species having ZW sex chromosomes, with 5 genomes of bird-of-paradise species newly produced in this work. We conclude that songbird sex chromosomes have undergone at least four steps of recombination suppression before their species radiation, producing a gradient pattern of pairwise sequence divergence termed ‘evolutionary strata’. Interestingly, the latest stratum probably emerged due to a songbird-specific burst of retrotransposon CR1-E1 elements at its boundary, or chromosome inversion on the W chromosome. The formation of evolutionary strata has reshaped the genomic architecture of both sex chromosomes. We find stepwise variations of Z-linked inversions, repeat and GC contents, as well as W-linked gene loss rate that are associated with the age of strata. Over 30 W-linked genes have been preserved for their essential functions, indicated by their higher and broader expression of orthologs in lizard than those of other sex-linked genes. We also find a different degree of accelerated evolution of Z-linked genes vs. autosomal genes among different species, potentially reflecting their diversified intensity of sexual selection. Our results uncover the dynamic evolutionary history of songbird sex chromosomes, and provide novel insights into the mechanisms of recombination suppression.