An essential cell cycle regulation gene causes hybrid inviability in Drosophila

Essential genes and species incompatibilities Crosses between two fruit fly species, Drosophila melanogaster and D. simulans , result in hybrid progeny that are all female. Although some of the genes responsible for this species barrier are known, the full complement of molecular determinants that lead to inviable males has remained mysterious. Phadnis et al. used mutagenesis and a sequencing-based genomic screen to link hybrid inviability to the cell cycle. The inviable males result from an interaction between three genes, one of which is essential, which precluded its identification with standard genetic screens. This strategy to identify speciation genes can be applied to other model and nonmodel systems. Science , this issue p. 1552