Chemoreceptor co-expression in Drosophila melanogaster olfactory neurons.


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Authors
Lin, Chun-Chieh 
Vulpe, Alina 
Afify, Ali 
Ballou, Sydney 
Abstract

Drosophila melanogaster olfactory neurons have long been thought to express only one chemosensory receptor gene family. There are two main olfactory receptor gene families in Drosophila, the odorant receptors (ORs) and the ionotropic receptors (IRs). The dozens of odorant-binding receptors in each family require at least one co-receptor gene in order to function: Orco for ORs, and Ir25a, Ir8a, and Ir76b for IRs. Using a new genetic knock-in strategy, we targeted the four co-receptors representing the main chemosensory families in D. melanogaster (Orco, Ir8a, Ir76b, Ir25a). Co-receptor knock-in expression patterns were verified as accurate representations of endogenous expression. We find extensive overlap in expression among the different co-receptors. As defined by innervation into antennal lobe glomeruli, Ir25a is broadly expressed in 88% of all olfactory sensory neuron classes and is co-expressed in 82% of Orco+ neuron classes, including all neuron classes in the maxillary palp. Orco, Ir8a, and Ir76b expression patterns are also more expansive than previously assumed. Single sensillum recordings from Orco-expressing Ir25a mutant antennal and palpal neurons identify changes in olfactory responses. We also find co-expression of Orco and Ir25a in Drosophila sechellia and Anopheles coluzzii olfactory neurons. These results suggest that co-expression of chemosensory receptors is common in insect olfactory neurons. Together, our data present the first comprehensive map of chemosensory co-receptor expression and reveal their unexpected widespread co-expression in the fly olfactory system.

Description
Keywords
Research Article, Neuroscience, olfactory receptors, Ionotropic Receptors, antennal lobe, glomeruli, sensory biology, mosquito, D. melanogaster, Anopheles coluzzii, D. sechellia
Journal Title
Elife
Conference Name
Journal ISSN
2050-084X
2050-084X
Volume Title
11
Publisher
eLife Sciences Publications, Ltd
Sponsorship
Wellcome Trust (203261/Z/16/Z)