Gene expression divergence and the origin of hybrid dysfunctions
Hybrids between closely related species are often sterile or inviable as a consequence of failed interactions between alleles from the different species. Most genetic studies have focused on localizing the alleles associated with these failed interactions, but the mechanistic/biochemical nature of the failed interactions is poorly understood. This review discusses recent studies that may contribute to our understanding of these failed interactions. We focus on the possible contribution of failures in gene expression as an important contributor to hybrid dysfunctions. Although regulatory pathways that share elements in highly divergent taxa may contribute to hybrid dysfunction, various studies suggest that misexpression may be disproportionately great in regulatory pathways containing rapidly evolving, particularly male-biased, genes. We describe three systems that have been analyzed recently with respect to global patterns of gene expression in hybrids versus pure species, each in Drosophila. These studies reveal that quantitative misexpression of genes is associated with hybrid dysfunction. Misexpression of genes has been documented in sterile hybrids relative to pure species, and variation in upstream factors may sometimes cause the over- or under-expression of genes resulting in hybrid sterility or inviability. Studying patterns of evolution between species in regulatory pathways, such as spermatogenesis, should help in identifying which genes are more likely to be contributors to hybrid dysfunction. Ultimately, we hope more functional genetic studies will complement our understanding of the genetic disruptions leading to hybrid dysfunctions and their role in the origin of species.
KeywordsHybrid sterility Hybrid inviability Gene expression Speciation Transcription Microarray
Unable to display preview. Download preview PDF.
We thank S. Dixon Schully for preparing an early draft of one section of this paper. Funding was provided by National Science Foundation grants 0211007 and 0314552.
- Causton HC, Quackenbush J, Brazma A (2003) Microarray gene expression data analysis: a beginner’s guide. Blackwell Publishing, OxfordGoogle Scholar
- Crawford DL (2001) Functional genomics does not have to be limited to a few select organisms. Genome Biol. 2: interactions1001. 1001–1001. 1002Google Scholar
- Darwin C (1859) The origin of species Random House, Inc., New YorkGoogle Scholar
- Ihmels J, Bergmann S, Barkai N (2004) Defining transcription modules using large-scale gene expression data. Bioinformatics: bth166Google Scholar
- Michalak P, Noor MAF (2004) Association of misexpression with sterility in hybrids of Drosophila simulans and D. mauritiana. J Mol Evol 59:277–282Google Scholar
- Muller HJ (1940) Bearings of the Drosophila work on systematics. In: Huxley J (ed) New systematics. Clarendon Press, Oxford, pp. 185–268Google Scholar
- Muller HJ (1942) Isolating mechanisms, evolution and temperature. Biol Symp 6:71–125Google Scholar
- Wu C-I, Perez DE, Davis AW, Johnson NA, Cabot EL, Palopoli MF and Wu M-L (1992) Molecular genetic studies of postmating reproductive isolation in Drosophila. In: Takahata N, Clark AG (ed) Molecular paleo-population biology. pp 191–212. Springer-VerlagGoogle Scholar