Pheromone binding proteins enhance the sensitivity of olfactory receptors to sex pheromones in Chilo suppressalis

Hetan Chang,Paolo Pelosi,Yang Liu,Shuanglin Dong,Guirong Wang,Ting Yang

doi:10.1038/srep13093

Abstract

Sexual communication in moths offers a simplified scenario to model and investigate insect sensory perception. Both PBPs (pheromone-binding proteins) and PRs (pheromone receptors) are involved in the detection of sex pheromones, but the interplay between them still remains largely unknown. In this study, we have measured the binding affinities of the four recombinant PBPs of Chilo suppressalis (CsupPBPs) to pheromone components and analogs and characterized the six PRs using the Xenopus oocytes expression system. Interestingly, when the responses of PRs were recorded in the presence of PBPs, we measured in several combinations a dramatic increase in signals as well as in sensitivity of such combined systems. Furthermore, the discrimination ability of appropriate combinations of PRs and PBPs was improved compared with the performance of PBPs or PRs alone. Besides further supporting a role of PBPs in the pheromone detection and discrimination, our data shows for the first time that appropriate combinations of PRs and PBPs improved the discrimination ability of PBPs or PRs alone. The variety of responses measured with different pairing of PBPs and PRs indicates the complexity of the olfaction system, which, even for the relatively simple task of detecting sex pheromones, utilises a highly sophisticated combinatorial approach.

Highlights

Insect OBPs are folded into a very compact and conserved structure made of six a-helices enveloping a hydrophobic binding pocket[18,19]
In order to investigate the functional relationships between the six PRs and the four PBPs in the complex process of detecting and discriminating the specific sex pheromones in C. suppressalis, we first mapped the expression of their genes in antennae and other parts of the body of adult females
The results here reported can provide a contribution towards understanding the complex interplay between pheromones, receptors and binding proteins and the specific roles played by these three partners

Summary

Introduction

Insect OBPs are folded into a very compact and conserved structure made of six a-helices enveloping a hydrophobic binding pocket[18,19]. As observed for the family of OBPs, within the large repertoire of ORs a subset of few members can be identified in Lepidoptera on the basis of sequence analysis as putative receptors for sex pheromones (PRs: pheromone receptors) Such assumption is mainly based on the identification of the first lepidopteran member of this sub-group in Bombyx mori[27]. Using the robust system of Xenopus oocytes to functionally characterise ORs, recent studies have addressed the question on the role of OBPs by adding this proteins to the test and recording responses to pheromones in their presence In experiments of this type, performed with the PRs of B. mori, Antheraea polyphemus and the diamond back moth Plutella xylostella, a stronger and more specific electrophysiological response was measured when the pheromone was applied together with the appropriate PBP26,32,33. A classification of these proteins into long, medium and short OBPs has been suggested based on such considerations[19]

Methods

Results

Conclusion