Functional Analysis of Two Odorant-Binding Proteins, MaltOBP9 and MaltOBP10, in Monochamus alternatus Hope.

Dong-Zhen Li,Rui-Nan Yang,Xiao-Feng Huang,Man-Qun Wang,Jing-Yuan Chen

doi:10.3389/fphys.2020.00317

Dong-Zhen Li, Rui-Nan Yang + Show 3 more

Open Access

https://doi.org/10.3389/fphys.2020.00317

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Abstract

Odorant-binding proteins (OBPs) are important for the perception of chemical signals by insects. Effective pest management strategies can be developed by understanding the host location mechanism and the physiological functions of OBPs in olfactory detection. In this study, we cloned two OBPs from Monochamus alternatus, where MaltOBP9 was highly expressed in multiple insect tissues and MaltOBP10 was highly expressed in the female antenna according to the results of qRT-PCR. The recombinant proteins were successfully purified in vitro. Immunocytochemistry indicated the high expression of MaltOBP9 and MaltOBP10 in the sensillum lymph of sensilla basiconica, sensilla trichodea, sensilla auricillica, and sensilla chaetica, thereby demonstrating their broad participation in semiochemical detection. Both proteins were localized in the inner cavity of mechanoreceptors and they exhibited broad binding abilities with volatiles from pine bark according to fluorescence competitive binding assays. Due to its broad binding ability and distribution, MaltOBP9 may be involved in various physiological processes as well as olfactory detection. MaltOBP10 appears to play a role in the fundamental olfactory recognition process of female adults according to its broad binding ability. These findings suggest that OBPs may have various physiological functions in insects, thereby providing novel insights into the olfactory receptive mechanism.

Highlights

The special and sensitive olfactory system of insects perceives infochemicals in the environment, such as plant volatiles and pheromones, and it affects the lifecycle of insects by regulating behaviors, such as foraging, aggregation, mating, spawning, dispersion, and defense (Zwiebel and Takken, 2004; Leal, 2013; Brito et al, 2016)
Based on the antennal transcriptome, specific primers were designed for MaltOBP9 and MaltOBP10, and applied in PCR (Supplementary Figure S1)
BLAST analyses showed that MaltOBP9 has four Cys residues and it is a minus-C Odorant-binding proteins (OBPs) whereas MaltOBP10 has six Cys residues and it is a classic OBP (Supplementary Figure S2)

Summary

Introduction

The special and sensitive olfactory system of insects perceives infochemicals in the environment, such as plant volatiles and pheromones, and it affects the lifecycle of insects by regulating behaviors, such as foraging, aggregation, mating, spawning, dispersion, and defense (Zwiebel and Takken, 2004; Leal, 2013; Brito et al, 2016). Olfactory sensation is an extremely complicated pathway that involves diverse proteins, including odorant-binding proteins (OBPs), chemosensory proteins (CSPs), odorant degrading enzymes (ODEs), odorant receptors (ORs), and sensory neuron. Functions of MaltOBPs From Monochamus alternatus membrane proteins (SNMPs) (Meiners et al, 2003; Benton et al, 2007; Jin et al, 2008; Venthur et al, 2015; Zheng et al, 2016). OBPs are considered to operate in the first step of chemical cue reception by combining and transporting lipophilic odorants across the sensillum lymph to ORs in the dendritic membranes of olfactory receptor neurons (Krieger et al, 1996; Laughlin et al, 2008; Brito et al, 2016). The signature of the classic OBPs is a pattern comprising of six cysteines in conserved positions, which are connected in the native protein by three interlocking disulfide bridges (Lescop et al, 2009; Zhuang et al, 2014; Brito et al, 2016). Other non-classical OBPs have been identified, including minus-C OBPs, which contain only four conserved cysteines, and plus-C OBPs, which contain more than six conserved cysteines (Zhou et al, 2004; Forêt and Maleszka, 2006; He et al, 2016)

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