Knockout of the odorant receptor co-receptor, orco, impairs feeding, mating and egg-laying behavior in the fall armyworm Spodoptera frugiperda

The olfactory transduction system of insects is involved in multiple behavioral processes such as foraging, mating, and egg-laying behavior. In the insect olfactory receptor neurons (ORNs), the odorant receptor coreceptor (Orco) is an obligatory component that is required for dimerization with odorant receptors (ORs) to form a ligand-gated ion channel complex. The ORs/Orco heteromeric complex plays a crucial role in insect olfaction. To explore the function of OR-mediated olfaction in the physiological behavior of the fall armyworm, Spodoptera frugiperda, we applied CRISPR/Cas9 genome editing to mutate its Orco gene and constructed a homozygous mutant strain of Orco (Orco-/-) by genetic crosses. Electroantennogram (EAG) analysis showed that the responses of Orco-/- male moths to two universal sex pheromones, Z9-14: Ac and Z7-12: Ac, were abolished. We found that Orco-/- males cannot successfully mate with female moths. An oviposition preference assay confirmed that Orco-/- female moths had a reduced preference for the optimal host plant maize. A larval feeding assay revealed that the time for Orco-/- larvae to locate the food source was significantly longer than in the wildtype. Overall, in the absence of Orco, the OR-dependent olfactory behavior was impaired in both larval and adult stages. Our results confirm that Orco is essential for multiple behavioral processes related to olfaction in the fall armyworm.

Automated summary

The olfactory transduction system of insects is involved in multiple behavioral processes such as foraging, mating, and egg-laying behavior. The ORs/Orco heteromeric complex plays a crucial role in insect olfaction. In this study, CRISPR/Cas9 genome editing was used to mutate the Orco gene in Spodoptera frugiperda, resulting in impaired olfactory behavior in both larval and adult stages.