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Sex-biased gene expression on the avian z chromosome: highly expressed genes show higher male-biased expression.

Author:
  • Sara Naurin
  • Dennis Hasselquist
  • Staffan Bensch
  • Bengt Hansson
Publishing year: 2012
Language: English
Publication/Series: PLoS ONE
Volume: 7
Issue: 10
Document type: Journal article
Publisher: Public Library of Science

Abstract english

Dosage compensation, the process whereby expression of sex-linked genes remains similar between sexes (despite heterogamety) and balanced with autosomal expression, was long believed to be essential. However, recent research has shown that several lineages, including birds, butterflies, monotremes and sticklebacks, lack chromosome-wide dosage compensation mechanisms and do not completely balance the expression of sex-linked and autosomal genes. To obtain further understanding of avian sex-biased gene expression, we studied Z-linked gene expression in the brain of two songbirds of different genera (zebra finch, Taeniopygia guttata, and common whitethroat, Sylvia communis) using microarray technology. In both species, the male-bias in gene expression was significantly higher for Z than for autosomes, although the ratio of Z-linked to autosomal expression (Z:A) was relatively close to one in both sexes (range: 0.89-1.01). Interestingly, the Z-linked male-bias in gene expression increased with expression level, and genes with low expression showed the lowest degree of sex-bias. These results support the view that the heterogametic females have up-regulated their single Z-linked homologues to a high extent when the W-chromosome degraded and thereby managed to largely balance their Z:A expression with the exception of highly expressed genes. The male-bias in highly expressed genes points towards male-driven selection on Z-linked loci, and this and other possible hypotheses are discussed.

Keywords

  • Biological Sciences

Other

Published
  • Sex chromosome evolution and sex-biased expression
  • CAnMove
  • Molecular Ecology and Evolution Lab
  • ISSN: 1932-6203
Dennis Hasselquist
E-mail: dennis [dot] hasselquist [at] biol [dot] lu [dot] se

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+46 46 222 37 08

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