A gene affecting the specificity of the chemosensory neurons of Drosophila

The sensilla on the proboscis and tarsi of Drosophila contain five neurons, four chemosensory and one mechanosensory1–3. The sugar-sensitive neuron, designated S, carries independent acceptor sites for pyranose, furanose and trehalose4–7. Two others, L1 and L2, respond to salts2. The fourth neuron, W, is inhibited by salts and sugars, and is believed to mediate detection of water. We describe here a gene in which mutations alter the neurons in such a way that the S cell is excited by salts. As a result, the mutant flies are strongly attracted by NaCl at concentrations which are repellent to the wild type. To our knowledge, this is the first instance of a mutation which changes the specificity of the chemosensory neurons.