Characterization of antennal chemosensilla and associated odorant binding as well as chemosensory proteins in the parasitoid wasp Microplitis mediator (Hymenoptera: Braconidae)

Shan-Ning Wang,Rui-Jun Li,Jing-Tao Liu,Zi-Yun Lu,Khalid Hussain Dhiloo,Yong-Jun Zhang,Adel Khashaveh,Shuang Shan

doi:10.1038/s41598-018-25996-3

Abstract

Odorant binding proteins (OBPs) and chemosensory proteins (CSPs) expressed in antennal chemosensilla are believed to be important in insect chemoreception. In the current study, we fully described the morphological characteristics of the antennal sensilla in parasitoid wasp Microplitis mediator and analyzed the expression patterns of OBPs and CSPs within the antennae. In M. mediator, eight types of sensilla were observed on the antennae. Sensilla basiconica type 2 and s. placodea with wall pores may be involved in olfactory perception, whereas s. basiconica type 1 and type 3 with tip pores may play gustatory functions. Among the 18 OBPs and 3 CSPs in M. mediator, 10 OBPs and 2 CSPs were exclusively or primarily expressed in the antennae. In situ hybridization experiments indicated that the 12 antennae-enriched OBPs and CSPs were mapped to five morphological classes of antennal sensilla, including s. basiconica (type 1–3), s. placodea and s. coeloconica. Within the antennae, most of OBP and CSP genes were expressed only in one type of sensilla indicating their differentiated roles in detection of special type of chemical molecules. Our data will lay a foundation to further study the physiological roles of OBPs and CSPs in antennae of parasitoid wasps.

Highlights

Parasitoid wasps, known to locate their suitable hosts in a complex environment are mediated largely by chemical cues
The specific physiological roles of Odorant binding proteins (OBPs) and chemosensory proteins (CSPs) in olfaction and gustation are remained poorly understood, it is widely believed that they play essential roles in transferring semiochemicals across the aqueous sensillum lymph to chemoreceptors in the dendrites of the chemosensory neurons[13,14]
Since the first insect OBPs were reported in the Lepidoptera[16], a large number of OBP and CSP genes are being identified in different insect species

Summary

Introduction

Parasitoid wasps, known to locate their suitable hosts in a complex environment are mediated largely by chemical cues. Several studies showed that the chemosensory sensilla (olfaction and gustation) used by parasitoid wasps to locate and evaluate their hosts are mostly present on their antennae[4,5,6,7]. Two families of small soluble proteins, odorant binding proteins (OBPs) and chemosensory proteins (CSPs) are believed to be involved in the chemical communication and perception in insects[13,14]. Only a part of OBP and CSP genes have specific or enriched expression in the antennae[17,22,23], and different OBPs and CSPs are expressed in different antennal sensilla[24,25,26,27]. The antennae have been found to contain both olfactory and gustatory sensilla, little is known whether OBPs or CSPs are expressed in antennal gustatory sensilla. Our results will lay a key foundation to further investigate the physiological roles of OBPs and CSPs in parasitic wasp chemoreception

Methods

Results

Conclusion