Abstract
Olfaction plays a dominant role in the mate-finding and host selection behaviours of the codling moth (Cydia pomonella), an important pest of apple, pear and walnut orchards worldwide. Antennal transcriptome analysis revealed a number of abundantly expressed genes related to the moth olfactory system, including those encoding the olfactory receptors (ORs) CpomOR1, CpomOR3 and CpomOR6a, which belong to the pheromone receptor (PR) lineage, and the co-receptor (CpomOrco). Using heterologous expression, in both Drosophila olfactory sensory neurones and in human embryonic kidney cells, together with electrophysiological recordings and calcium imaging, we characterize the basic physiological and pharmacological properties of these receptors and demonstrate that they form functional ionotropic receptor channels. Both the homomeric CpomOrco and heteromeric CpomOrco + OR complexes can be activated by the common Orco agonists VUAA1 and VUAA3, as well as inhibited by the common Orco antagonists amiloride derivatives. CpomOR3 responds to the plant volatile compound pear ester ethyl-(E,Z)-2,4-decadienoate, while CpomOR6a responds to the strong pheromone antagonist codlemone acetate (E,E)-8,10-dodecadien-1-yl acetate. These findings represent important breakthroughs in the deorphanization of codling moth pheromone receptors, as well as more broadly into insect ecology and evolution and, consequently, for the development of sustainable pest control strategies based on manipulating chemosensory communication.
Highlights
Previous transcriptome-based studies[10,11], reported 58 putative codling moth ORs, of which 12 are grouped in the PR-clade
We compared the open reading frames (ORFs) sequence with the updated transcript variants found by Walker et al (2016)[11], and determined that this sequence corresponds to CpomOR6a
Seven transmembrane domains with an intracellular localization for the N-terminus were predicted for CpomOR6a, CpomOR3, CpomOR1 and CpomOrco (Fig. 1), reflecting the typical topology of insect ORs27
Summary
Previous transcriptome-based studies[10,11], reported 58 putative codling moth ORs, of which 12 are grouped in the PR-clade. While we were unable to detect a response of CpomOR1 to any of the native ligands tested, CpomOR3 responded to pear ester as well as the analogous methyl-(E,Z)-2-4-decadienoate and CpomOR6a responded to codlemone acetate ((E,E)8,10-dodecadien-1-yl acetate) a strong pheromone antagonist of the codling moth[26]. These findings represent important breakthroughs in understanding the mechanisms of codling moth attraction to biologically relevant odours and, for developing innovative pest control strategies based on disrupting olfactory communication
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