An Antennae-Specific Odorant-Binding Protein Is Involved in Bactrocera dorsalis Olfaction

Zhao Liu,Ian W Keesey,Jin-Jun Wang,Xiao-Fei Liang,Li Xu,Guy Smagghe,Zhong-Ren Lei

doi:10.3389/fevo.2020.00063

Abstract

Insect antennae are important olfactory organs that house high concentrations of odorant-binding proteins (OBPs) in the sensillum lymph. Previous studies in other insects have shown that OBPs play important roles in transporting odorants and enhancing the sensitivity of the olfactory system. However, the functions of OBPs in the oriental fruit fly, Bactrocera dorsalis, especially those specifically expressed in antennae, have not been fully elucidated. In this study, cDNA libraries were constructed from both the male and female antennal transcriptome, and twenty OBPs were identified in total. The expression profiles of these OBPs were examined in the adult antenna, head, thorax, leg, and abdomen of both sexes. Seven of the identified OBP genes had significantly higher expression in both the male and female antennae than in other tissues, while the transcript levels of the remaining OBPs varied across different tissues. Regarding the function of antenna-specific OBPs, we targeted Bdorsobp2 as a representative for further RNA interference (RNAi) and identified via electrophysiology a decrease in detection of a potential species-specific a potent attractant, methyl eugenol. Moreover, subsequent behavioral assay data showed that the behavioral response of B. dorsalis toward this odorant decreased when Bdorobp2 was silenced with injection of double-stranded RNA (dsRNA). Combined, these results support our initial hypothesis that antennae-specific OBPs are of critical importance for insect odorant detection, sensitivity, and behavior.

Highlights

Antennae are the most important olfactory organs for insects to detect chemosensory compounds from the environment and to regulate their behaviors, including sexual attraction, mating or courtship, aggregation, host plant orientation, and the selection of oviposition sites
20 previously identified odorant-binding proteins (OBPs) candidate sequences were obtained from the B. dorsalis antennae transcriptome, including 16 sequences that had the full length of open reading frames (ORFs) and the hallmarks of the classic OBP subfamily: a signal peptide and six conserve cysteine residues (Figure 1)
Starting with the hypothesis that OBPs are vital for insect olfaction, and should be abundantly or exclusively expressed in olfactory tissues, the transcript levels of these candidate OBP genes were examined in different tissues, including the antennae, heads, thoraxes, legs, and abdomens of both male and female adults by quantitative polymerase chain reaction (qPCR) experiments

Summary

Introduction

Antennae are the most important olfactory organs for insects to detect chemosensory compounds from the environment and to regulate their behaviors, including sexual attraction, mating or courtship, aggregation, host plant orientation, and the selection of oviposition sites These semiochemicals enter the antennae via pores on the olfactory sensilla, which contain high concentrations of odorant-binding proteins (OBPs) in the sensillum lymph. Bdorobp Regulates Bactrocera dorsalis Olfaction olfaction, OBPs have been thoroughly studied in various insect orders, including Lepidoptera, Coleoptera, and Diptera (especially the genus Drosophila) (Leal, 2005; Pelosi et al, 2006) Both physiological and behavioral evidence has shown that insect OBPs were important for odorant recognition and sensitivity. These characteristics make OBPs potential candidates for insect pest management (IPM), and provide potential applications that offer more environmentally friendly solutions than insecticides

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Results

Conclusion