Functional Characteristics, Electrophysiological and Antennal Immunolocalization of General Odorant-Binding Protein 2 in Tea Geometrid, Ectropis obliqua.

Ya-Li Zhang,Ji-Zhong Yu,Hong-Chun Cui,Xiao-Bin Fu,Lei Zhao,Hong-Liang Li

doi:10.3390/ijms19030875

Abstract

As one of the main lepidopteran pests in Chinese tea plantations, Ectropis obliqua Warren (tea geometrids) can severely decrease yields of tea products. The olfactory system of the adult tea geometrid plays a significant role in seeking behaviors, influencing their search for food, mating partners, and even spawning grounds. In this study, a general odorant-binding protein (OBP) gene, EoblGOBP2, was identified in the antennae of E. obliqua using reverse transcription quantification PCR (RT-qPCR). Results showed that EoblGOBP2 was more highly expressed in the antennae of males than in females relative to other tissues. The recombinant EoblGOBP2 protein was prepared in Escherichia coli and then purified through affinity chromatography. Ligand-binding assays showed that EoblGOBP2 had a strong binding affinity for some carbonyl-containing tea leaf volatiles (e.g., (E)-2-hexenal, methyl salicylate, and acetophenone). Electrophysiological tests confirmed that the male moths were more sensitive to these candidate tea plant volatiles than the female moths. Immunolocalization results indicated that EoblGOBP2 was regionally confined to the sensilla trichoid type-II in the male antennae. These results indicate that EoblGOBP2 may be primarily involved in the olfactory activity of male E. obliqua moths, influencing their ability to sense tea leaf volatiles. This study provides a new perspective of insect GOBPs and implies that olfactory function can be used to prevent and control the tea geometrid.

Highlights

Insects sense semiochemicals emanating from host plants through their olfactory systems [1]
We found that EoblGOBP2 had between 61.9 and 98.1% homologies to other GOBP2s
Pyralidae moths (e.g., L. sticticalis) and Tortricidae moths (e.g., Argyresthia conjugella) were divided into another branch in the phylogenetic tree (Figure 2). This indicates that EoblGOBP2 is a conservative gene within most of the lepidopteran family

Summary

Introduction

Insects sense semiochemicals emanating from host plants through their olfactory systems [1]. This plays an important role in the survival and reproduction of insect species in the natural environment, influencing behaviors such as feeding, courtship, and locating spawning sites [2]. Olfactory systems of insects are mainly composed of soluble binding proteins, olfactory receptors, and odor-degrading enzymes [3]. Soluble odorant-binding proteins (OBPs) (mainly existing in the antennal sensillar lymph of insects) are involved in odor reception and are thought to carry lipophilic odorants to the olfactory receptor cells through hydrophilic surroundings [4,5]. According to amino acids’ sequence homologies, distribution patterns, and binding ligand category, insect OBPs are generally divided into three subfamilies, including general OBPs (GOBPs), pheromone-binding proteins (PBPs), and antennal specific proteins (ASPs) [11]

Methods

Results

Conclusion