Identification of Hybrid Sterility Genes in Drosophila

Reproductive isolation is central to the maintenance of species boundaries. The evolution of post-zygotic genome incompatibilities is a widespread mechanism caused by the disruption of allelic interactions in hybrids; it ensures that matings between genetically isolated populations result in either inviable or sterile individuals, thereby acting as an impediment to gene flow. Hybrid male sterility (HMS) has been recognized since Darwin, yet only few of the underlying factors have been identified to date and whether certain classes of genes are more prone to evolve incompatibilites is an open question. Here, we investigate the nature and molecular mechanism of a genomic incompatibility that lies behind an autosomal hybrid sterility factor mapped in a small region in chromosome 3R between Drosophila simulans and D. mauritiana. We demonstrate the role of two loci, TAF1 and agt, as novel functional classes of HMS genes and suggest that the incompatibility lies in the accumulation of functional divergence between the two parental genomes.