A novel family of divergent seven-transmembrane proteins: Candidate odorant receptors in Drosophila

Although insects have proven to be valuable models for exploring the functi on, organization, and development of the olfactory system, the receptor mol ecules that bind odors have not been identified in any insect. We have deve loped a novel search algorithm, used it to search the Drosophila genomic se quence database, and identified a large multigene family encoding seven tra nsmembrane domain proteins that are expressed in olfactory organs. We show that expression is restricted to subsets of olfactory receptor neurons (ORN s) for a number of these genes. Different members of the family initiate ex pression at different times during antennal development. Some of the genes are not expressed in a mutant of the Acj6 POU-domain transcription factor, a mutant in which a subset of ORNs show abnormal odorant specificities.