Sex biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution

B. Vicoso, V. Kaiser, D. Bachtrog, PNAS 110 (2013) 6453–6458.

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Journal Article | Published
Author
Vicoso, BeatrizIST Austria ; Kaiser, Vera B; Bachtrog, Doris
Abstract
Sex chromosomes originate from autosomes. The accumulation of sexually antagonistic mutations on protosex chromosomes selects for a loss of recombination and sets in motion the evolutionary processes generating heteromorphic sex chromosomes. Recombination suppression and differentiation are generally viewed as the default path of sex chromosome evolution, and the occurrence of old, homomorphic sex chromosomes, such as those of ratite birds, has remained a mystery. Here, we analyze the genome and transcriptome of emu (Dromaius novaehollandiae) and confirm that most genes on the sex chromosome are shared between the Z and W. Surprisingly, however, levels of gene expression are generally sex-biased for all sex-linked genes relative to autosomes, including those in the pseudoautosomal region, and the male-bias increases after gonad formation. This expression bias suggests that the emu sex chromosomes have become masculinized, even in the absence of ZW differentiation. Thus, birds may have taken different evolutionary solutions to minimize the deleterious effects imposed by sexually antagonistic mutations: some lineages eliminate recombination along the protosex chromosomes to physically restrict sexually antagonistic alleles to one sex, whereas ratites evolved sex-biased expression to confine the product of a sexually antagonistic allele to the sex it benefits. This difference in conflict resolution may explain the preservation of recombining, homomorphic sex chromosomes in other lineages and illustrates the importance of sexually antagonistic mutations driving the evolution of sex chromosomes.
Publishing Year
Date Published
2013-04-16
Journal Title
PNAS
Volume
110
Issue
16
Page
6453 - 6458
IST-REx-ID

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Vicoso B, Kaiser V, Bachtrog D. Sex biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution. PNAS. 2013;110(16):6453-6458. doi:10.1073/pnas.1217027110
Vicoso, B., Kaiser, V., & Bachtrog, D. (2013). Sex biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution. PNAS, 110(16), 6453–6458. https://doi.org/10.1073/pnas.1217027110
Vicoso, Beatriz, Vera Kaiser, and Doris Bachtrog. “Sex Biased Gene Expression at Homomorphic Sex Chromosomes in Emus and Its Implication for Sex Chromosome Evolution.” PNAS 110, no. 16 (2013): 6453–58. https://doi.org/10.1073/pnas.1217027110.
B. Vicoso, V. Kaiser, and D. Bachtrog, “Sex biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution,” PNAS, vol. 110, no. 16, pp. 6453–6458, 2013.
Vicoso B, Kaiser V, Bachtrog D. 2013. Sex biased gene expression at homomorphic sex chromosomes in emus and its implication for sex chromosome evolution. PNAS. 110(16), 6453–6458.
Vicoso, Beatriz, et al. “Sex Biased Gene Expression at Homomorphic Sex Chromosomes in Emus and Its Implication for Sex Chromosome Evolution.” PNAS, vol. 110, no. 16, National Academy of Sciences, 2013, pp. 6453–58, doi:10.1073/pnas.1217027110.

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