Binding characteristics of odor binding protein EsigOBP8 from Endoclita signifier and volatile compounds from Eucalyptus spp.

Objective Endoclita signifier is one of the most serious borer pests that has been found in Guangxi and Guangdong regions of southern China in recent years, causing damage to eucalyptus. To develop efficient prevention and control techniques, this paper aims to find key olfactory recognition genes of E. signifier and analyze the structural features and binding characteristics the key olfactory gene of EsigOBP8 providing theoretical support for developing new prevention and control strategies.

Method EsigOBP8 sequence based on transcriptome screening was obtained using RACE. Its three-dimensional structure was constructed using SWISS-MODEL, and its quality was evaluated using evaluation software such as Procheck. Molecular docking experiments between EsigOBP8 and 64 main volatiles of eucalyptus were conducted using AutoDock Tools software.

Result The full length of EsigOBP8 mRNA was 805 bp, full length of ORF was 549 bp, encoding 182 amino acids, 5′ non-coding region 108 bp, with eukaryotic cap structure (m7GPPPN), 3′ non-coding region 148 bp, with ployA tail structure. The similarity between EsigOBP8 and Anopheles gambiae OBP47 (NT_078266.2) was 33%. The results of molecular docking showed that EsigOBP8 had the strongest binding ability with (−)-fenchone, followed by thujopsene, (+)-aromadendrene, (−)-camphor and eucalyptol. The key binding sites for 5 eucalyptus volatiles were identified as ALA-126, ILE-25, and PHE-129 residues, with hydrophobic interactions serving as the predominant binding force.

Conclusion As the predominant volatile compoundin eucalyptus, eucalyptol serves as the primary ligand that binds to the odorant-binding protein EsigOBP8. This interaction can induce electrophysiological responses in E. signifer larvae, and such olfactory recognition plays a crucial role in host location by 3rd instar E. signifer larvae. Additionally, although (−)-camphor, (+)-aromadendrene and thujopsene are trace volatiles in the affected trunks of eucalyptus trees, they are usually attractant to insects and may also be involved in olfactory recognition process of larvae of E. signifier. In conclusion, it is suggested that EsigOBP8 is a key protein involved in host recognition of the 3rd instar larvae, especially in recognition of eucalyptol.