Odorant receptor co-receptor Orco is upregulated by methyl eugenol in male Bactrocera dorsalis (Diptera: Tephritidae)

Bactrocera dorsalis is a destructive fruit-eating pest that causes severe economic damage to the fruit and vegetable industry. Methyl eugenol (ME) has been widely used as an effective sexual attractant for male fruit flies through olfactory perception. However, the molecular mechanism underlying the olfactory perception of ME remains unknown. Here, we report the characterization and functional analysis of a newly discovered cDNA that encodes a Drosophila melanogaster odorant receptor co-receptor Orco ortholog in B. dorsalis. qRT-PCR analysis revealed that it was abundantly expressed in the antenna of adult B. dorsalis. Notably, Orco was upregulated by ME in the antenna of male flies. Mature males of B. dorsalis showed significant taxis toward ME within 0.5 h, and Orco was significantly upregulated in the attracted adults within the same period. Silencing Orco through the ingestion of dsRNA reduced the attractive effects of ME. These data suggest that Orco may play an essential role in ME attraction in the olfactory signal transduction pathway.