Genome-Wide Screen for Candidate Genes Underlying Phenotypic Divergence and Hybrid Dysfunction in Drosophila Pseudoobscura and Its Close Relatives

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Understanding how new species are formed is a major question in Biology. When new species evolve from an ancestral one, their hybrids usually have several developmental or physiological problems, like infertility or lower vigor. Those problems are the result of incompatible genetic changes that have occurred in each one of the species during and after speciation. Trying to pinpoint what are those genetic changes has been difficult using traditional genetic methods. However, recently developed molecular methods that allow investigators obtain a snapshot of gene activity in all genes from an organism at any given time ("microarrays") provide an alternative, or complement, to traditional genetic methods to uncover the genetic changes underlying hybrid incompatibilities. We will use microarrays to explore this question in a classic group of fruit fly species: Drosophila pseudoobscura and its close relatives D. persimilis and D. pseudoobscura bogotana. We will investigate gene activity in hybrid sterile males from those species to first determine what genes have unusual levels of activity and will follow up only genes with unusual activity that are involved in reproduction. We will then establish whether a subset of those genes is indeed involved in hybrid sterility using traditional genetic methods (i.e. a series of genetic crosses). Finally, we will determine whether genetic changes that have occurred at those genes or at other genes that affect their activity are indeed responsible for the hybrid incompatibilities. This approach is likely to provide major insights into the identity of genes responsible for hybrid incompatibilities in these and other group of species. The results of the proposed research will be of general interest to biologists and will allow us training students in functional genomics and evolutionary genetics. We are fully committed to integrate individuals from underrepresented groups in our research program. Finally, the identification of putative hybrid male sterility genes in Drosophila could lead to the discovery of similar genes also involved in human male infertility, and thus the health implications of the proposed research may be large.