Functional characterization of sex pheromone receptors in Spodoptera frugiperda, S. exigua, and S. litura moths

Abstract

Moths possess an extremely sensitive and diverse sex pheromone processing system, in which pheromone receptors (PRs) are essential to ensure communication between mating partners. Functional properties of some PRs are conserved among species, which is important for reproduction. However, functional differentiation has occurred in some homologous PR genes, which may drive species divergence. Here, using genome analysis, 17 PR genes were identified from Spodoptera frugiperda, S. exigua, and S. litura, which belong to 6 homologous groups (odorant receptor [OR]6, 11, 13, 16, 56, and 62); of which 6 PR genes (OR6, OR11, OR13, OR16, OR56, and OR62) were identified in S. frugiperda and S. exigua, and 5 PR genes were identified in S. litura, excluding OR62. Using heterologous expression in Xenopus oocytes, we characterized the functions of PR orthologs including OR6, OR56, and OR62, which have not been clarified in previous studies. OR6 orthologs were specifically tuned to (Z,E)-9,12-tetradecadienyl acetate (Z9,E12-14:OAc), and OR62 orthologs were robustly tuned to Z7-12:OAc in S. frugiperda and S. exigua. The optimal ligand for OR56 was Z7-12:OAc in S. frugiperda, but responses were minimal in S. exigua and S. litura. In addition, SfruOR6 was male antennae-specific, whereas SfruOR56 and SfruOR62 were male antennae-biased. Our study further clarified the functional properties of PRs in 3 Spodoptera moth species, providing a comprehensive understanding of the mechanisms of intraspecific communication and interspecific isolation in Spodoptera.

Conserved Odorant Receptors Involved in Nonanal-Induced Female Attractive Behavior in Two Spodoptera Species

“…frugiperda and S. litura, except for those responding to sex pheromones, − , and SlituOR12 exclusively responded to cis-3-hexenyl acetate . In the present study, we identified a conserved OR clade (SfruOR47 clade) including eight members from eight moth species.…”

“…39 For S. frugiperda and S. litura, nonanal may serve as a signal indicating the presence of flowers, as females require nectar consumption to ensure proper ovary development. Although a wide range of ORs from S. littoralis have been functionally characterized, 10 little is known about the function of ORs in S. frugiperda and S. litura, except for those responding to sex pheromones, [11][12][13]21 and SlituOR12 exclusively responded to cis-3-hexenyl acetate. 40 In the present study, we identified a conserved OR clade (SfruOR47 clade) including eight members from eight moth species.…”

“…frugiperda and S. litura has primarily focused on the ORs that respond to sex pheromones, − little is known about the molecular mechanisms underlying detecting plant volatiles in these two Spodoptera species.…”

Molecular mechanism of sex pheromone perception in male Mythimna loreyi revealed by in vitro system

“…First, 5 M. loreyi PRs in traditional PR clade (branch 1–7) all grouped most closely with the M. separate homologs, reflecting a close evolutionary relationship between the two congeneric species. Second, branch 1 and 2 were conserved for Spodoptera genus, in which PRs were correspondingly able to sense acetates and alcohol pheromones, 37,68 and branches 4 and 5 were specific for two Mythimna species; while branches 3, 6 and 7 were formed by PRs of both genera. Third, no ligand has been identified for PRs in branch 6, suggesting that these PRs might be conserved in function for some special ligands, which needs to be identified by expanding the chemicals tested.…”

“…The upper part shows the sex pheromone components of each species, with stars indicating the major pheromone components, while check marks indicating the minor components. [69][70][71][72][73] Moth species and the PR ligand profiles included Mythimna loreyi (Mlor) (this study), Spodoptera frugiperda (Sfru), 35,37,68 Mythimna separata (Msep), 66,67 Spodoptera litura (Slitu) 35,68,74 and Spodoptera exigua (Sexi), 68,75 Spodoptera littoralis (Slitt). 35,76,77 The dots represent the responses obtained by the Xenolus oocyte system, and the triangles represent responses by in vivo heterologous expression in Drosophila OSNs.…”