OS9: a novel olfactory gene of Drosophila expressed in two olfactory organs.

A novel olfactory gene, OS9, has been identified in Drosophila by subtractive hybridization. OS9 transcripts have been detected in the third antennal segment, the primary olfactory organ in Drosophila, and in the maxillary palp, which has recently been shown to have olfactory function. The OS9 gene thus represents a molecular link between two distinct olfactory tissues in Drosophila. Little if any OS9 expression has been detected in other segments of the antenna or in other tissues examined. The gene is located in region 38AB on the cytogenetic map. OS9 encodes a protein of 159 amino acids, which contains a putative leucine zipper. Polyclonal antibodies raised against the C-terminal half of the encoded protein react with a 24 kD antennal protein. Antisera raised against both C-terminal and N-terminal halves of the OS9 protein appear to react with cell nuclei in both the third antennal segment and the maxillary palp; interestingly, both antisera also stain cells in the head, including photoreceptor nuclei, as if OS9 were an olfactory-specific member of a family of nuclear proteins, possibly transcription factors.