Identification of odorant binding proteins and chemosensory proteins in Microplitis mediator as well as functional characterization of chemosensory protein 3.

Yong Peng,Yao Zheng,Ye-Qing Yang,Ke-Ming Li,Jing-Tao Liu,Yong-Jun Zhang,Shan-Ning Wang,Shuang Shan,Yu-Yuan Guo,Rui-Jun Li

doi:10.1371/journal.pone.0180775

Abstract

Odorant binding proteins (OBPs) and chemosensory proteins (CSPs) play important roles in transporting semiochemicals through the sensillar lymph to olfactory receptors in insect antennae. In the present study, twenty OBPs and three CSPs were identified from the antennal transcriptome of Microplitis mediator. Ten OBPs (MmedOBP11–20) and two CSPs (MmedCSP2–3) were newly identified. The expression patterns of these new genes in olfactory and non-olfactory tissues were investigated by real-time quantitative PCR (qPCR) measurement. The results indicated that MmedOBP14, MmedOBP18, MmedCSP2 and MmedCSP3 were primarily expressed in antennae suggesting potential olfactory roles in M. mediator. However, other genes including MmedOBP11–13, 15–17, 19–20 appeared to be expressed at higher levels in body parts than in antennae. Focusing on the functional characterization of MmedCSP3, immunocytochemistry and fluorescent competitive binding assays were conducted indoors. It was found that MmedCSP3 was specifically located in the sensillum lymph of olfactory sensilla basiconca type 2. The recombinant MmedCSP3 could bind several types of host insects odors and plant volatiles. Interestingly, three sex pheromone components of Noctuidae insects, cis-11-hexadecenyl aldehyde (Z11-16: Ald), cis-11-hexadecanol (Z11-16: OH), and trans-11-tetradecenyl acetate (E11-14: Ac), showed high binding affinities (Ki = 17.24–18.77 μM). The MmedCSP3 may be involved in locating host insects. Our data provide a base for further investigating the physiological roles of OBPs and CSPs in M. mediator, and extend the function of MmedCSP3 in chemoreception of M. mediator.

Highlights

In insects, behaviors of host identification, mating-partners, and locating oviposition sites are regulated largely by volatile chemical cues [1, 2]
The results indicated that MmedOBP14, MmedOBP18, MmedCSP2 and MmedCSP3 were primarily expressed in antennae suggesting potential olfactory roles in M. mediator
The BLASTx results indicated that ten odorant binding proteins (OBPs) and two chemosensory proteins (CSPs) were newly identified (Table 2), which were named as MmedOBP11–20 and MmedCSP2–3, respectively, based on our previous work [20]

Summary

Introduction

Behaviors of host identification, mating-partners, and locating oviposition sites are regulated largely by volatile chemical cues [1, 2]. These odor molecules are usually perceived by chemosensory sensilla located on their antennae [3]. OBPs and CSPs were synthesized in non-neuronal support cells and secreted in the lymph of chemosensilla at extraordinarily high concentrations [8]. Both OBPs and CSPs are small (12–18 kDa) and soluble proteins which have capacities to bind reversibly small molecules [9, 10]. Most of OBPs are considered to be antenna-specific, whereas CSPs are more widely distributed in different tissues of the insect body suggesting their multi-roles [15,16,17]

Methods

Results

Conclusion