Recent Insights into Insect Olfactory Receptors and Odorant-Binding Proteins

Abstract

Human and insect olfaction share many general features, but insects differ from mammalian systems in important ways. Mammalian olfactory neurons share the same overlying fluid layer in the nose, and neuronal tuning entirely depends upon receptor specificity. In insects, the olfactory neurons are anatomically segregated into sensilla, and small clusters of olfactory neurons dendrites share extracellular fluid that can be independently regulated in different sensilla. Small extracellular proteins called odorant-binding proteins are differentially secreted into this sensillum lymph fluid where they have been shown to confer sensitivity to specific odorants, and they can also affect the kinetics of the olfactory neuron responses. Insect olfactory receptors are not G-protein-coupled receptors, such as vertebrate olfactory receptors, but are ligand-gated ion channels opened by direct interactions with odorant molecules. Recently, several examples of insect olfactory neurons expressing multiple receptors have been identified, indicating that the mechanisms for neuronal tuning may be broader in insects than mammals. Finally, recent advances in genome editing are finding applications in many species, including agricultural pests and human disease vectors.

Identifying the Key Role of Plutella xylostella General Odorant Binding Protein 2 in Perceiving a Larval Attractant, (E,E)-2,6-Farnesol

“…This finding is consistent with existing reports on the function of insect GOBPs. As a class of proteins highly expressed in herbivorous insect antennae, GOBPs are dominant OBPs to recognize general plant odorants, they bind to various HPVs and play essential roles in regulating feeding, oviposition, and many other behaviors. − For example, SlitGOBP2 in S. litura shows high binding activity to a wide range of HPVs, including farnesol, 2-pentadecanone, and linoleic acid .…”

Host plant odour and sex pheromone are integral to mate finding in codling moth

“…CpomOR3 was found in a codling moth antennal transcriptome and its main ligand, according to a functional assay in Drosophila olfactory sensory neurons, is pear ester (Bengtsson et al 2014; Walker et al 2016; Gonzalez et al 2017). Male-biased pheromone receptors respond mainly to sex pheromones, while general ORs are tuned to environmental odors including plant volatiles (Fleischer et al 2018; Ha & Smith 2022; Yang et al 2022).…”

Chemotactic responses and parasitism of Trichogramma pretiosum after successive generations in Spodoptera frugiperda

“…Various proteins are involved in odor reception in insects, such as odorant-binding proteins (OBPs), chemosensory proteins (CSPs), odorant receptors (ORs), ionotropic receptors (IRs), gustatory receptors (GRs), and sensory neuron membrane proteins (SNMPs), playing a crucial role in detecting, transporting, and/or recognizing specific odor molecules (Leal, 2013;Ha & Smith, 2022;Kohlmeier & Billeter, 2023). The ability to exploit novel host sources T A B L E 1 Deviance analysis for parasitism and emergence rate of Trichogramma pretiosum in Ephestia kuehniella or Spodoptera frugiperda eggs when T. pretiosum parasitoids from E. kuehniella eggs or from the 1st, 2nd, or 3rd generations in S. frugiperda eggs were tested in two-choice assays.…”

“…Various proteins are involved in odor reception in insects, such as odorant‐binding proteins (OBPs), chemosensory proteins (CSPs), odorant receptors (ORs), ionotropic receptors (IRs), gustatory receptors (GRs), and sensory neuron membrane proteins (SNMPs), playing a crucial role in detecting, transporting, and/or recognizing specific odor molecules (Leal, 2013; Ha & Smith, 2022; Kohlmeier & Billeter, 2023). The ability to exploit novel host sources often requires changes in the chemosensory system as it enables an individual to identify, locate, and become attracted to a different host.…”