Olfaction in Drosophila: Coding, genetics and e-genetics

Odor coding in Drosophila is examined at both the cellular and molecular le vels. Functional analysis of individual olfactory receptor neurons (ORNs) b y single-unit electrophysiology has shown that ORNs divide into discrete cl asses, with each class exhibiting a characteristic odor response spectrum. Extensive analysis of ORNs in the maxillary palp has revealed six such clas ses, which are combined in sensilla according to a strict pairing rule. in order to identify the odor receptor genes that determine the odor specifici ty of these ORN classes, a new algorithm was designed to search DNA databas es for proteins with a particular structure, as opposed to a particular seq uence. The algorithm identified a large family of genes likely to encode od or receptors. The acj6 gene, originally identified in a screen for mutants defective in olfactory behavior, encodes a transcription factor that regula tes a subset of these receptor genes, and is likely to play a critical role in the process by which ORNs select which receptors to express.