Identification of Candidate Chemosensory Receptors in the Antennae of the Variegated Cutworm, Peridroma saucia Hübner, Based on a Transcriptome Analysis.

Ya-Lan Sun,Shao-Li Wang,Nan Gu,Jun-Feng Dong

doi:10.3389/fphys.2020.00039

Abstract

Insect chemoreception, including olfaction and gustation, involves several families of genes, including odorant receptors (ORs), ionotropic receptors (IRs), and gustatory receptors (GRs). The variegated cutworm Peridroma saucia Hübner (Lepidoptera: Noctuidae) is a worldwide agricultural pest that causes serious damage to many crops. To identify such olfactory and gustatory receptors in P. saucia, we performed a systematic analysis of the antennal transcriptome of adult P. saucia through Illumina sequencing. A total of 103 candidate chemosensory receptor genes were identified, including 63 putative ORs, 10 GRs, 24 IRs, and 6 ionotropic glutamate receptors (iGluRs). Phylogenetic relationships of these genes with those from other species were predicted, and specific chemosensory receptor genes were analyzed, including ORco, pheromone receptors (PRs), sugar receptors, CO2 receptors, and IR co-receptors. RT-qPCR analyses of these annotated genes revealed that 6 PRs were predominantly expressed in male antennae; 3 ORs, 1 GR, 2 IRs, and 2 iGluRs had higher expression levels in male than in female antennae; and 14 ORs, 1 GR, and 3 IRs had higher expression levels in female than in male antennae. This research increases the understanding of olfactory and gustatory systems in the antennae of P. saucia and facilitates the discovery of novel strategies for controlling this pest.

Highlights

Insects rely on chemoreception to recognize and discriminate chemical cues in the external environment in order to mate, oviposit, locate hosts, and avoid predators (Hansson and Stensmyr, 2011; Leal, 2013)
We reported on the sequencing, assembly, and annotation of the antennal transcriptome of the polyphagous crop pest P. saucia
The number of identified chemoreceptor genes is comparable to that reported for the lepidopteran antennal transcriptomes of Spodoptera littoralis (60 odorant receptors (ORs), 17 gustatory receptors (GRs), and 17 ionotropic receptors (IRs)) and Galleria mellonella (46 ORs and 25 IRs) (Walker et al, 2019; Zhao et al, 2019)

Summary

Introduction

Insects rely on chemoreception to recognize and discriminate chemical cues in the external environment in order to mate, oviposit, locate hosts, and avoid predators (Hansson and Stensmyr, 2011; Leal, 2013). Insect chemosensation is mainly mediated by three families of chemosensory receptor genes including odorant receptors (ORs) (Clyne et al, 1999; Vosshall et al, 1999), gustatory receptors (GRs) (Clyne et al, 2000), and ionotropic receptors (IRs) (Benton et al, 2009). These genes are usually expressed in the primary olfactory appendages, the antennae. Genes in the OR family differ greatly among insect species (except for ORco), both in sequence and in the total number of ORs expressed (Engsontia et al, 2008; Zhou et al, 2015)

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