Identification and Functional Characterization of General Odorant Binding Proteins in Orthaga achatina

The Female-Biased General Odorant Binding Protein 2 of Semiothisa cinerearia Displays Binding Affinity for Biologically Active Host Plant Volatiles

Herbivorous insects rely on volatile chemical cues from host plants to locate food sources and oviposition sites. General odorant binding proteins (GOBPs) are believed to be involved in the detection of host plant volatiles. In the present study, one GOBP gene, ScinGOBP2, was cloned from the antennae of adult Semiothisa cinerearia. Reverse-transcription PCR and real-time quantitative PCR analysis revealed that the expression of ScinGOBP2 was strongly biased towards the female antennae. Fluorescence-based competitive binding assays revealed that 8 of the 27 host plant volatiles, including geranyl acetone, decanal, cis-3-hexenyl n-valerate, cis-3-hexenyl butyrate, 1-nonene, dipentene, α-pinene and β-pinene, bound to ScinGOBP2 (KD = 2.21-14.94 μM). The electrical activities of all eight ScinGOBP2 ligands were confirmed using electroantennography. Furthermore, oviposition preference experiments showed that eight host volatiles, such as decanal, cis-3-hexenyl n-valerate, cis-3-hexenyl butyrate, and α-pinene, had an attractive effect on female S. cinerearia, whereas geranyl acetone, 1-nonene, β-pinene, and dipentene inhibited oviposition in females. Consequently, it can be postulated that ScinGOBP2 may be implicated in the perception of host plant volatiles and that ScinGOBP2 ligands represent significant semiochemicals mediating the interactions between plants and S. cinerearia. This insight could facilitate the development of a chemical ecology-based approach for the management of S. cinerearia.

Molecular and Functional Characterization of Three General Odorant-Binding Protein 2 Genes in Cydia pomonella (Lepidoptera: Tortricidae)

General odorant-binding proteins (GOBPs) play a crucial role in the detection of host plant volatiles and pheromones by lepidopterans. Previous studies identified two duplications in the GOBP2 gene in Cydia pomonella. In this study, we employed qRT-PCR, protein purification, and fluorescence competitive binding assays to investigate the functions of three GOBP2 genes in C. pomonella. Our findings reveal that CpomGOBP2a and CpomGOBP2b are specifically highly expressed in antennae, while CpomGOBP2c exhibits high specific expression in wings, suggesting a potential divergence in their functions. Recombinant proteins of CpomGOBP2a, CpomGOBP2b, and CpomGOBP2c were successfully expressed and purified, enabling an in-depth exploration of their functions. Competitive binding assays with 20 host plant volatiles and the sex pheromone (codlemone) demonstrated that CpomGOBP2a exhibits strong binding to four compounds, namely butyl octanoate, ethyl (2E,4Z)-deca-2,4-dienoate (pear ester), codlemone, and geranylacetone, with corresponding dissolution constants (Ki) of 8.59993 μM, 9.14704 μM, 22.66298 μM, and 22.86923 μM, respectively. CpomGOBP2b showed specific binding to pear ester (Ki = 17.37481 μM), while CpomGOBP2c did not exhibit binding to any tested compounds. In conclusion, our results indicate a functional divergence among CpomGOBP2a, CpomGOBP2b, and CpomGOBP2c. These findings contribute valuable insights for the development of novel prevention and control technologies and enhance our understanding of the evolutionary mechanisms of olfactory genes in C. pomonella.

The binding affinity of two general odorant binding proteins in Spodoptera frugiperda to general volatiles and insecticides

Spodoptera frugiperda is a kind of polyphagous pest, and can damage a large number different host plants around the worldwide. The molecular mechanisms of two general odorant binding proteins (GOBPs) binding with general volatiles and insecticides are still blank. In this study, we investigated the function of two GOBPs in S. frugiperda, by expressing two SfruGOBPs and tested the binding affinities by the fluorescence competition binding assays. The results exhibited that SfruGOBP1 has binding affinities to 4 of 38 general volatiles and 3 of 7 insecticides. In contrast, SfruGOBP2 showed a broader ligand-binding spectrum to 21 volatiles and 4 insecticides, suggesting SfruGOBP2 may plays a more important role in perceiving host volatiles than SfruGOBP1. Furthermore, we used molecular docking and site-directed mutagenesis assay to explored the key amino acid residues of two SfruGOBP to insecticides ligand. This study provides some valuable information to exploring the olfactory mechanism of two GOBPs bound the host plant volatiles and insecticides in S. frugiperda.