Chemosensory Gene Families in Ectropis grisescens and Candidates for Detection of Type-II Sex Pheromones

Abstract

Tea grey geometrid (Ectropis grisescens), a devastating chewing pest in tea plantations throughout China, produces Type-II pheromone components. Little is known about the genes encoding proteins involved in the perception of Type-II sex pheromone components. To investigate the olfaction genes involved in E. grisescens sex pheromones and plant volatiles perception, we sequenced female and male antennae transcriptomes of E. grisescens. After assembly and annotation, we identified 153 candidate chemoreception genes in E. grisescens, including 40 odorant-binding proteins (OBPs), 30 chemosensory proteins (CSPs), 59 odorant receptors (ORs), and 24 ionotropic receptors (IRs). The results of phylogenetic, qPCR, and mRNA abundance analyses suggested that three candidate pheromone-binding proteins (EgriOBP2, 3, and 25), two candidate general odorant-binding proteins (EgriOBP1 and 29), six pheromone receptors (EgriOR24, 25, 28, 31, 37, and 44), and EgriCSP8 may be involved in the detection of Type-II sex pheromone components. Functional investigation by heterologous expression in Xenopus oocytes revealed that EgriOR31 was robustly tuned to the E. grisescens sex pheromone component (Z,Z,Z)-3,6,9-octadecatriene and weakly to the other sex pheromone component (Z,Z)-3,9-6,7-epoxyoctadecadiene. Our results represent a systematic functional analysis of the molecular mechanism of olfaction perception in E. grisescens with an emphasis on gene encoding proteins involved in perception of Type-II sex pheromones, and provide information that will be relevant to other Lepidoptera species.

A novel lineage of candidate pheromone receptors for sex communication in moths

“…Here, we evidence that SlitOR5 is a new type I PR that belongs to a distinct early diverging lineage for which a role in pheromone detection had never been demonstrated. Together with the findings that PRs for Type 0 (Yuvaraj et al, 2017) and one PR for type II pheromones (Li et al, 2017) group in distinct paralogous lineages also unrelated to the PR clade, our data suggest that lepidopteran PRs have evolved four times in four paralogous lineages. Whether the SlitOR5 lineage has evolved from ORs that detected structurallyrelated plant volatiles -as has been proposed for type 0 (Yuvaraj et al, 2017) and classical type I PRs -remains elusive.…”

Comparison of male antennal morphology and sensilla physiology for sex pheromone olfactory sensing between sibling moth species: Ectropis grisescens and Ectropis obliqua (Geometridae)

“…We consider that the OSNs population coding accounts for OR function and expression. However, to date, only a few studies of the expression of relevant candidate olfactory genes have been carried out in E. grisescens and E. obliqua (Li et al, ; Sun et al, ). Further comparative studies of function, response profiles, and expression patterns of ORs between the two species are required.…”

“…For E. obliqua , the components are Z3,epo6,Z9–18:H, Z3,Z6,Z9–18:H, and (Z,Z)‐3,9‐ cis ‐6,7‐epoxy‐nonadecadiene (Z3,epo6,Z9–19:H) at a ratio of 4:2:4 (Luo, Li, Cai, Bian, & Chen, ). Several studies have focused on volatile analytical chemistry, behavior, antennal morphology, and molecular biology of olfactory receptors (ORs) and genetic analysis of candidate olfactory binding proteins of the two species (Li et al, ; Luo et al, ; Ma, Bian, et al, ; Ma, Xiao, et al, ; Sun et al, ; Zhang et al, ), but no experiments have investigated sensillum physiology.…”

Functional Characteristics, Electrophysiological and Antennal Immunolocalization of General Odorant-Binding Protein 2 in Tea Geometrid, Ectropis obliqua

“…Both are from the Japanese giant looper moth, Ascotis selenaria cretacea [ 23 ]. By using transcriptome analysis, some other PBPs have also been recently found in the legs [ 24 ], and whole bodies of third-instar E. obliqua larvae [ 25 ], and in the antennae of Ectropis grisescens [ 26 ]. However, limited studies have focused on characterizing the olfactory system and functional characteristics of E. obliqua .…”