Journal of Advanced Research

Journal of Advanced Research

Volume 43, January 2023, Pages 1-12
Journal of Advanced Research

Original Article
A female-biased odorant receptor tuned to the lepidopteran sex pheromone in parasitoid Microplitis mediator guiding habitat of host insects

https://doi.org/10.1016/j.jare.2022.03.006Get rights and content
Under a Creative Commons license
open access

Highlights

  • Female parasitoid wasps (Microplitis mediator) are attracted by the sex pheromone of the turnip moth (Agrotis segetum).

  • The female-biased odorant receptor MmedOR49 tuned to the Z5-10:Ac (the main sex pheromone component of the turnip moth) in vitro.

  • Z5-10: Ac strongly binds to MmedOR49 by the formation of hydrogen bonds with the key residues (His 80, Ile 81, and Arg 84).

  • The behavioral response of female M. mediator to Z5-10:Ac was strongly diminished when MmedOR49 was downregulated by RNAi.

  • MmedOR49 is involved in the locating of parasitic wasp host habitats using the perception of host sex pheromone.

Abstract

Introduction

The parasitoid wasp Microplitis mediator is an important natural enemy of the turnip moth Agrotis segetum and other Noctuidae pests. In our field observation, it was fortuitously discovered that sex pheromone traps used for A. segetum also attract female wasps, verified by a simulated field condition dual-choice laboratory assay. Therefore, it was hypothesized that olfactory recognition could be crucial in this process. In this regard, a female-biased odorant receptor of the wasp, MmedOR49, attracted our attention.

Objectives

To unravel the significance of the female-biased MmedOR49 regulating host pheromone recognition.

Methods

Expression analysis (fluorescence in situ hybridization; quantitative realtime PCR), in vitro (two-electrode voltage-clamp recordings) and in vivo (RNAi combined with behavioral assessments) functional studies, and bioinformatics (structural modeling and molecular docking) were carried out to investigate the characteristics of MmedOR49.

Results

MmedOR49 expression was detected in the antennae of females by FISH. Quantification indicated that the expression level of MmedOR49 increased significantly after adult emergence. In vitro functional study revealed that MmedOR49 was specifically tuned to cis-5-decenyl acetate (Z5-10:Ac), the major sex pheromone component of A. segetum. Molecular docking showed that Z5-10:Ac strongly bound to the key amino acid residues His 80, Ile 81, and Arg 84 of MmedOR49 through hydrogen bonding. Behavioral assays indicated that female wasps were significantly attracted by Z5-10:Ac in a three-cage olfactometer. RNAi targeting further confirmed that MmedOR49 was necessary to recognize Z5-10:Ac, as female wasps lost their original behavioral responses to Z5-10:Ac after down-regulation of the MmedOR49 transcript.

Conclusion

Although M. mediator is a larval endoparasitoid, female wasps have a behavioral preference for a sex pheromone component of lepidopteran hosts. In this behavior, for female M. mediator, MmedOR49 plays an important role in guiding the habitat of host insects. These data provide a potential target for enhancing natural enemy utilization and pest control.

Keywords

Microplitis mediator
Lepidopteran pest
Odorant receptor
Sex pheromone
Z5-10:Ac
Host habitat location

Cited by (0)

Peer review under responsibility of Cairo University.

1

These authors contributed equally to this work.