Identification and Expression Profile of Olfactory Receptor Genes Based on Apriona germari (Hope) Antennal Transcriptome.

Jia-Li Qian,Bo Chu,Guo-Chang Lv,Jia Ye,Long-Wa Zhang,Yu-Jun Liu,Long Sun,Zhao-Qun Li,Ding-Ze Mang

doi:10.3389/fphys.2020.00807

Abstract

Insects’ olfactory receptor plays a central role in detecting chemosensory information from the environment. Odorant receptors (ORs) and ionotropic receptors (IRs) are two types of olfactory receptors, and they are essential for the recognition of ligands at peripheral neurons. Apriona germari (Hope) (Coleoptera: Cerambycidae) is one of the most serious insect pests that cause damage to economic trees and landscaping trees, resulting in massive environmental damages and economic losses. Olfactory-based management strategy has been suggested as a promising strategy to control this wood-boring beetle. However, the olfactory perception mechanism in A. germari is now almost unknown. In the present study, RNA sequencing analysis was used to determine the transcriptomes of adult A. germari antennae. Among 36,834 unigenes derived from the antennal assembly, we identified 42 AgerORs and three AgerIRs. Based on the tissue expression pattern analysis, 27 AgerORs displayed a female-biased expression. Notably, AgerOR3, 5, 13, 33, and 40 showed a significant female-biased expression and were clustered with the pheromone receptors of Megacyllene caryae in the phylogenetic tree, suggesting that these AgerORs could be potential pheromone receptors for sensing male-produced sex pheromones in A. germari. The AgerIRs expression profile demonstrated that AgerIR2 had high expression levels in male labial palps, suggesting that this receptor may function to detect female-deposited trail-sex pheromone blend of A. germari. In addition, the phylogenetic tree showed that the Orco gene of five cerambycidae species was highly conservative. These results provide a foundation for further studies on the molecular mechanisms of olfactory chemoreception in A. germari apart from suggesting novel targets for the control of this pest in the future.

Highlights

Insects have developed a set of highly specialized and sensitive olfactory system that can accurately identify miniscule and highly specific odor substances in a complex natural environment and perform adaptive behaviors by long-term selective evolution (Jacquin-Joly and Merlin, 2005; Martin et al, 2011)
Less than one-fifth of short reads (500 bp) are more likely to be assembled into unigenes
Coleoptera is the first order of Insecta and one of the most important orders in forestry, and the longhorn beetle is one of the larger groups of Coleoptera, with 45,000 species in the world and more than 3,100 species known in China (Zhang, 2011)

Summary

Introduction

Insects have developed a set of highly specialized and sensitive olfactory system that can accurately identify miniscule and highly specific odor substances in a complex natural environment and perform adaptive behaviors by long-term selective evolution (Jacquin-Joly and Merlin, 2005; Martin et al, 2011). It is thought that olfactory recognition in insects is a complex process involving multiple chemosensory-associated proteins, including chemosensory proteins, odorant receptors (ORs), odorant-binding proteins, odorant-degrading enzymes, ionotropic receptors (IRs), and sensory neuron membrane proteins (Sato and Touhara, 2009; Leal, 2013). Since the discovery of olfactory receptors in Drosophila melanogaster in 1999, the olfactory receptor system has been a key link in understanding the molecular recognition mechanism of insects’ chemical signals. This provides the basis for the specific control of agricultural and forestry pests through insect smell

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