Odorant receptor coexpression and multi-expression in the dengue mosquito

Drosophila olfactory sensory neurons tend to express a single ligand-specific receptor, following a one-receptor-per-neuron rule expected to apply broadly across insects. Recent work challenges this view by showing that some neurons in the mosquito Aedes aegypti coexpress multiple receptors. However, the full extent and nature of coexpression in Ae. aegypti remains unclear. We sequenced the transcriptomes of 46,000 female antennal neurons to resolve all olfactory neuron subtypes and identify expressed receptors. Half of all subtypes coexpress multiple receptors. However, coexpression occurs almost exclusively among receptors from the same family; cross-family coexpression of odorant receptors with ionotropic receptors is rare. We also document a phenomenon called multi-expression, wherein one receptor is expressed in multiple neuron subtypes, often alongside distant paralogs. Drosophila provides rare examples of both coexpression and multi-expression, suggesting that Drosophila and Aedes are not fundamentally different, but instead located at different positions along a continuum likely to encompass diverse insects.