Odorant detection in a locust exhibits unusually low redundancy
Hetan Chang, Anjana P. Unni, Megha Treesa Tom, Qian Cao, Yang Liu, Guirong Wang, Lucas Cortés Llorca, Sabine Brase, Sascha Bucks, Kerstin Weniger, Sonja Bisch-Knaden, Bill S. Hansson, Markus Knaden
Abstract
Olfactory coding, from insects to humans, is canonically considered to involve considerable across-fiber coding already at the peripheral level, thereby allowing recognition of vast numbers of odor compounds. We show that the migratory locust has evolved an alternative strategy built on highly specific odorant receptors feeding into a complex primary processing center in the brain. By collecting odors from food and different life stages of the locust, we identified 205 ecologically relevant odorants, which we used to deorphanize 48 locust olfactory receptors via ectopic expression in Drosophila. Contrary to the often broadly tuned olfactory receptors of other insects, almost all locust receptors were found to be narrowly tuned to one or very few ligands. Knocking out a single receptor using CRISPR abolished physiological and behavioral responses to the corresponding ligand. We conclude that the locust olfactory system, with most olfactory receptors being narrowly tuned, differs from the so-far described olfactory systems.