Function and evolution of Ir52 receptors in mate detection in Drosophila.

Identifying a suitable mating partner is an ancient and critical biological problem. How a fruit fly distinguishes a fly of the same species from flies of innumerable related species remains unclear. We analyze the Ir52 receptors, expressed in taste neurons on the fly legs and encoded by a cluster of genes. We find that the cluster shows dynamic evolution, rapidly expanding and contracting over evolutionary time. We develop a novel in vivo expression system and find that Ir52 receptors respond differently to pheromone extracts of different fly species. The receptors are activated by some compounds and inhibited by others, with different receptors showing distinct response profiles. Circuit mapping shows that Ir52 neurons are pre-synaptic to sexually dimorphic neurons that overlap with neurons acting in courtship behavior. Our results support a model in which Ir52 receptors detect information about the species of a potential mating partner.