LAUSR

BACKGROUND Biological control of pest insects by parasitoid wasps is an effective and environmentally friendly strategy comparing to synthetic pesticides. Successful courtship and host search of parasitoid wasps are important to the biological control efficiency and are often mediated by chemically odorant cues. Odorant receptor co-receptor (Orco) gene plays an essential role in the perception of odors in insects. However, the functions of Orco in mating and host searching behaviors of parasitoid wasps remain underexplored. RESULTS We identified the full-length Orco genes of four Drosophila parasitoid species in Leptopilina genus, including L. heterotoma, L. boulardi, L. syphax and L. drosophilae. The results of sequence alignment and membrane-topology analysis showed that Leptopilina Orcos had similar amino acid sequences and topology structures. Phylogenetic analysis revealed that Leptopilina Orcos were highly conserved. Furthermore, the results of quantitative real-time PCR showed that all four Orco genes had a typical antennae-biased tissue expression pattern. After knocking down Orco in these different parasitoid species, we found Orco-deficient male parasitoid wasps lost the courtship ability but not the females. Moreover, the Orco-deficient female parasitoid wasps presented impaired host searching performance and decreased oviposition rates. CONCLUSION Our study demonstrates that Orcos are essential in mating and host searching behaviors of parasitoid wasps. To our knowledge, this is the first time that the functions of Orco genes are characterized in parasitoid wasps, which broadens our understanding of the chemoreception basis of parasitoid wasps and contributes to developing advanced pest management strategies. This article is protected by copyright. All rights reserved.