Molecular evolution of odorant-binding protein genes OS-E and OS-F in Drosophila

The Drosophila olfactory genes OS-E and OS-F are members of a family of gen es that encode insect odorant-binding proteins (OBPs). OBPs are believed to transport hydrophobic odorants through the acqueous fluid within olfactory , sensilla to the underlying receptor proteins. The recent discovery of a l arge family of olfactory receptor genes in Drosophila raises new questions about the function, diversity, regulation,, and evolution of the OBP family . We have investigated the OS-E and OS-F genes in a variety of Drosophila s pecies. These studies highlight potential regions of functional significanc e in the OS-E and OS-F proteins, which may include a region required for in teraction with receptor proteins. Our results suggest that the two genes ar ose by an ancient gene duplication, and that in some lineages, one or the o ther. gene has been lust. In D. virilis, the OS-F gene shows a different sp atial pattern of expression than in D, melanogaster: One of the OS-F intron s shows a striking degree of conservation between the two species, and rye identify a putative regulatory sequence within this intron. Finally, a phyl ogenetic analysis places both OS-E and OS-F within a large family of insect OBPs and OBP-like proteins.