The functional characterization of key odorant receptors in lepidopteran fruit pests

Numerous Lepidopteran species are prominent pests of fruit crops, resulting in tremendous economic losses. These arthropods find and consume or oviposit upon fruits by way of olfaction, which is achieved through interactions between proteins, called odorant receptors (Ors), and environmental compounds. Ors are transmembrane ligand-gated ion channels located on sensory neurons that selectively bind these compounds to produce a neuronal response. This study functionally characterizes Or22, which is highly conserved in Lepidoptera. In the codling moth, Cydia pomonella, Or22 (CpomOr22) responds to apple headspace volatiles. In our study, we utilized a library of 189 volatile organic compounds and a heterologous cell expression system to identify ligands that activate CpomOr22 , Lobesia botrana Or22 (LborOr22), Hedya nubifera Or22 (HnubOr22), and Pieris rapae Or22 (PrapOr22). We discovered that the receptors responded in a consistent and dose-dependent manner to undecanal, an eleven-carbon aldehyde commonly found in plant volatiles and insect pheromones, and to an eleven-carbon lactone, gamma-undecalactone. While we observed a greater magnitude of response to undecanal, the EC50 was lower for gamma-undecalactone, indicating that Or22 may be more sensitive to the lactone. These results enhance our understanding of odorant receptor function in Lepidoptera and provide a basis for further basic research and the development of novel control strategies for pest species.