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Open Access Research article

Gene expression analysis of the ovary of hybrid females of Xenopus laevis and X. muelleri

John H Malone12* and Pawel Michalak2

Author Affiliations

1 Department of Biology, The University of Texas Arlington, Box 19498, Arlington, Texas, 76010, USA

2 Laboratory of Cellular and Developmental Biology, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Department of Health and Human Services, Building 50, Room 3341, Bethesda, Maryland, 20892, USA

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BMC Evolutionary Biology 2008, 8:82  doi:10.1186/1471-2148-8-82

Published: 10 March 2008

Abstract

Background

Interspecific hybrids of frogs of the genus Xenopus result in sterile hybrid males and fertile hybrid females. Previous work has demonstrated a dramatic asymmetrical pattern of misexpression in hybrid males compared to the two parental species with relatively few genes misexpressed in comparisons of hybrids and the maternal species (X. laevis) and dramatically more genes misexpressed in hybrids compared to the paternal species (X. muelleri). In this work, we examine the gene expression pattern in hybrid females of X. laevis × X. muelleri to determine if this asymmetrical pattern of expression also occurs in hybrid females.

Results

We find a similar pattern of asymmetry in expression compared to males in that there were more genes differentially expressed between hybrids and X. muelleri compared to hybrids and X. laevis. We also found a dramatic increase in the number of misexpressed genes with hybrid females having about 20 times more genes misexpressed in ovaries compared to testes of hybrid males and therefore the match between phenotype and expression pattern is not supported.

Conclusion

We discuss these intriguing findings in the context of reproductive isolation and suggest that divergence in female expression may be involved in sterility of hybrid males due to the inherent sensitivity of spermatogenesis as defined by the faster male evolution hypothesis for Haldane's rule.