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Expression data from testes and abdomen in fertile and sterile introgression males

ABSTRACT: Postmating reproductive isolation is often manifested as hybrid male sterility, for which X-linked genes are over-represented. In contrast, X-linked gene are significantly under-represented among testis-expressing gene.This seeming contradiction may be germane to the X:autosome imbalance hypothesis on hybrid sterility ,in which the X-linked effect is mediated mainly through the misexpression of autosomal genes. We compared gene expression in fertile and sterile males in the hybrids between two Drosophila species. These hybrid males differ only in a small region of the X chromosome containing the OdsH locus of hybrid sterility. Of genes expressed in the testis, autosomal genes were indeed more likely to be misexpressed than X-linked genes under the steriizing action of OdsH.

ORGANISM(S): Drosophila simulans Drosophila melanogaster

PROVIDER: GSE21734 | GEO | 2010/05/19

SECONDARY ACCESSION(S): PRJNA127351

REPOSITORIES: GEO

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Project description:The X chromosome has a large effect on hybrid dysfunction, particularly hybrid male sterility. Although the evidence for this so-called large-X effect is clear, its molecular causes are not yet fully understood. One possibility is that, under certain conditions, evolution proceeds faster in X-linked loci than in their autosomal counterparts due to both natural selection and their hemizygosity in males (i.e. Faster-X effect), an effect that is expected to be greatest in genes with male-biased expression. Here I studied variation in transcript abundance within and between species in Drosophila yakuba, D. santomea and their hybrid males to evaluate both the faster-X and large-X effects at the level of genome-wide gene expression. I found that expression in X-linked male-biased genes evolves faster than in their autosomal counterparts, an effect that is accompanied by a unique reduction in gene expression polymorphism. Although we do not know the precise relationship between nucleotide and gene expression changes, elevated divergence to polymorphism ratios are consistent with Darwinian selection driving expression differences between species in X-linked male-biased genes, likely enhanced by male hemizygosity. Abundant changes in both cis- and trans-regulatory elements underlie regulatory gene expression divergence in the majority of the genes analyzed despite the recent split of the two sister species. I detected a large-X effect on regulation of expression in hybrid males, affecting mostly male-biased genes but also, to a lesser degree, nonsex-biased genes. Interestingly this misexpression is concentrated mostly in autosomal genes, likely facilitated by the rapid evolution of sex-linked trans-acting factors. I conclude that the faster evolution of X-linked male-biased genes, at both protein and expression levels, can contribute to explain the large effect of the X chromosome on hybrid male sterility, possibly mediating autosomal misexpression through cis-trans interactions.

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Expression data from testes and abdomen in fertile and sterile introgression males

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