Odour-driven behaviours sniffed out

To date, the neural mechanisms and genetics behind odour-driven behaviour are still poorly understood. The neuroanatomical and functional properties of the fruit fly, Drosophila melanogaster are similar but less complex than mammals, making it ideal for study. Researchers with EU funding for the project OLFACTORYIGLURS (Olfactory perception in Drosophila: analysis of a novel iGluR-related family of odorant receptors) explored odour-driven behaviours in the fly.

Drosophila olfactory receptors called ionotrophic receptors (IRs) are structurally related to the ionotropic glutamate receptors (iGluRs) that are found in vertebrate nervous systems. Scientists focused on IRs to elucidate the function and evolution of olfactory receptors as well as the representation of sensory cues in the brain.

Comprehensive evolutionary genomics and in situ expression analysis revealed two sub-families of IRs that are part of the olfactory system in Protostomia. This branch of the animal kingdom includes arthropods, nematodes, and molluscs. The 'antennal IRs' are found in insects whereas the species-specific 'divergent IRs' are expressed in peripheral and internal gustatory neurons, suggesting a role for them in taste sensing.

Considerable efforts also went into determining the molecular architecture of IRs as well as their neural circuits using electrophysiological recordings and cell imaging. Experiments provided novel insight into peripheral IR architecture and their function. An interesting perspective with numerous practical applications, these IRs could also be looked upon as custom-designed chemoreceptors.

Studies on IR neural circuits helped researchers determine how IRs detect chemical stimuli and the corresponding spatiotemporal patterns of neural activity in the brain. As a result, they could now compare the properties of IR chemosensory systems with other chemosensory receptors, providing deeper insight into IR development and function. Through manipulation of individual IR sensory pathways, researchers could also investigate odour-driven behaviour in organisms.

Project outcomes have applications in pest control through olfactory-based behaviour modulation as well as pollutant detection and clinical diagnosis. These findings are of importance to chemical ecologists, neuroscientists, evolutionary biologists and biomedical researchers.