Abstract

Olfaction is crucial in many insects for critical behaviors, including those regulating survival and reproduction. Insect odorant-binding proteins (OBPs) function in the first step of the olfactory system and play an essential role in the perception of odorants, such as pheromones and host chemicals. The oriental fruit fly, Bactrocera dorsalis, is a destructive fruit-eating pest, due to its wide host range of up to 250 different types of fruits and vegetables, and this fly causes severe economic damage to the fruit and vegetable industry. However, OBP genes have not been largely identified in B. dorsalis. Based on our previously constructed B. dorsalis cDNA library, ten OBP genes were identified in B. dorsalis for the first time. A phylogenetic tree was generated to show the relationships among the 10 OBPs of B. dorsalis to OBP sequences of two other Dipteran species, including Drosophila melanogaster and the mosquito Anopheles gambiae. The expression profiles of the ten OBPs in different tissues (heads, thoraxes, abdomens, legs, wings, male antennae and female antenna) of the mated adults were analyzed by real-time PCR. The results showed that nine of them are highly expressed in the antenna of both sexes, except BdorOBP7. Four OBPs (BdorOBP1, BdorOBP4, BdorOBP8, and BdorOBP10) are also enriched in the abdomen, and BdorOBP7 is specifically expressed in leg, indicating that it may function in other biological processes. This work will provide insight into the roles of OBPs in chemoreception and help develop new pest-control strategies.

Highlights

  • Olfaction is essential for insects in the location of hosts and the detection of pheromones during the recognition and location of mates

  • We report for the first time the large identification and tissue distribution of odorant binding proteins (OBPs) in Tephritid fruit flies. qRT-PCR revealed that each of the ten OBPs had abundant expression in antenna, except BdorOBP7, suggesting that the B. dorsalis OBP genes identified in the current study may play an important part in insect olfaction (Figure 4)

  • This work presents for the first time a study on the OBPs in Tephritid fruit flies, which are of major economic importance in agriculture

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Summary

Introduction

Olfaction is essential for insects in the location of hosts and the detection of pheromones during the recognition and location of mates. The olfactory system in insects consists of three main types of proteins: odorant binding proteins (OBPs), odorant receptors (ORs) and odorant-degrading esterases (ODEs) [1]. Insect OBPs are water-soluble proteins that often consist of 120–150 amino acids present in the chemosensory organs of insects These proteins are able to bind various hydrophobic odorant molecules in the environment and transport them through the hemolymph to the ORs at the dendrite membrane of the olfactory sensory neurons with antennae. It has been demonstrated that different OBPs display distinct odorant-binding specificity in a single moth species [15,19,20] All of these studies revealed that OBPs play significant roles in insect olfactory systems. This work presents for the first time a study of the OBPs of the invasive agricultural pest B. dorsalis, which may provide more molecular targets for B. dorsalis control and insight into insect olfaction research, providing an essential foundation for the development of efficient, simple, green and sustainable pest control strategies

Results and Discussion
Phylogenetic Analysis of Dipteran OBPs
Tissue Expression Pattern of the OBP Genes
Insect Rearing
Identification of the OBP Genes and Sequence Analysis
Phylogenetic Analysis
Total RNA Isolation and cDNA Synthesis
Expression Pattern Analysis of OBPs by Quantitative Real-time PCR
Conclusions
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