Acid sensing by the Drosophila olfactory system

We are familiar with the unpleasant and often irritating odour associated with acids, but whereas acid receptors are known to underlie the detection of sour tastes, no acid-sensing neurons were known in the olfactory system. Greg Suh and colleagues now report the identification of such neurons in the olfactory system of the fruitfly, Drosophila melanogaster. Acid sensing also requires the transmembrane protein IR64a to be expressed in those neurons. IR64a is not sufficient by itself to determine acid recognition, but its requirement is the first known function for a member of the recently discovered ionotropic receptor family of putative odorant receptors.