Mutagenesis of odorant coreceptor Orco reveals the distinct role of olfaction between sexes in Spodoptera frugiperda

Odorant receptor(OR)is crucial for insects to detect and recognize external chemical cues closely related to their survival.The insect OR forms a heteromeric complex composed of a ligand-specific receptor and a ubiquitously odorant receptor coreceptor(Orco).This study used the CRISPR/Cas9 technique to knock out(KO)Orco and reveal its essential role in acting on OR-meditated olfactory behavior in a critical invasive agricultural pest,the fall armyworm(FAW),Spodoptera frugiperda.Electroantennogram(EAG)results suggested that the Orco mutants of both male and female moths severely reduced their electrophysiological responses to the eight tested plant volatiles and two sex pheromones.However,the Orco gene played distinct roles in mating behavior between sexes:the mating behavior was fully disrupted in mutated males but not in mutated females.The oviposition result indicated that the Orco KO females displayed reduced egg laying by 24.1%compared with the mated wild type(WT)females.Overall,these results strongly suggest that Orco is an excellent target for disrupting FAW’s normal behavior and provides a feasible pest control approach.

Expression and functional characterization of odorant-binding protein 2 in the predatory mite Neoseiulus barkeri

Olfaction plays a crucial role for arthropods in foraging,mating,and oviposition.The odorant-binding protein(OBP)gene is considered one of the most important olfactory genes.However,little is known about its functions in predatory mites.Here,we used Neoseiulus barkeri,an important commercialized natural pest control,to explore the chemosensory characteristics of OBP.In this study,N.barkeri was attracted by methyl salicylate(MeSA)and showed higher crawling speeds under MeSA treatment.Then,we identified and cloned an OBP gene named Nbarobp2 and analyzed its expression profiles in the predatory mite.Nbarobp2 was 663 bp,was highly expressed in larval and nymphal stages,and was significantly upregulated in N.barkeri under MeSA treatment.Nbarobp2 encoded 202 amino acid residues with a molecular weight of 23 kDa(after removing the signal peptide).Sequence comparisons revealed that the OBPs in Arachnida shared 6 conserved cysteine sites,but were distinguishable from the OBPs of Insecta on the phylogenetic tree.RNA interference,Western blotting,and binding affinity assays further proved that Nbarobp2 was involved in volatile perception in predatory mites.This study shed light on the functional characteristics of OBPs in predatory mites,providing a new insight for better biological control.