Identification and function of sex pheromones and their receptors in Drosophila

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Insects not only use their senses of smell and taste to find the animal or plant hosts from which they feed and to find sites for laying eggs, but also to communicate with each other. Mating is the outcome of successful courtship, and courtship depends on communication between males and females. Recently, we found that a large part of the olfactory system in the fruit fly Drosophila, an insect that is used widely in biological research, appears to be dedicated to smelling fly odours. This suggests olfactory sex pheromones may play an important role in its reproductive behaviour. The aim of this project is to identify new olfactory sex pheromones in Drosophila and to analyze their function in courtship. In the flies' antennae, odours interact with odor receptors, encoded by the Odor receptor gene (Or) family. These odor receptors are expressed in the membranes of sensory neurons. The neurons encode information about the quality, intensity and temporal characteristics of odours in electrical signals. The olfactory sensory neurons are located in the antenna of the fly in structures called sensilla, and we can record the electrical activity of the neurons through an electrode placed into the sensilla. We found that trichoid sensilla, which are one morphological type, hold neurons that respond to fly odours. There are twelve Or genes expressed in the trichoids. We will use a previously developed assay system to test each of the receptors' sensitivity to fly odours. We will then identify the components in the fly odours that activate the receptors. Finally in behavioural experiments, we will explore how the flies use their receptors to distinguish suitable from unsuitable mates. Fruit flies belong to the order of the Diptera. The Diptera also include biting flies and mosquitoes that transmit serious diseases such as malaria, dengue fever and trypanosomiasis ('sleeping sickness' in humans). An understanding of sex pheromone communication in one fly species may elucidate general principles of Dipteran courtship, and may lead to new strategies of insect control by giving us the tools to disrupt the insects' reproductive behaviour.