Molecular basis of (E)-β-farnesene-mediated aphid location in the predator Eupeodes corollae.

(E)-β-farnesene (EBF) is an important chemical cue mediating interactions between plants, aphids, and natural enemies. This chemical has two origins, being secreted by aphid as an alarm pheromone and also produced by the attacked plants as a semiochemical attracting natural enemies. Despite the important role of this volatile chemical, little is known on the molecular mechanisms mediating the attraction of natural enemies to EBF. Here, we first verified that the larvae and adults of aphid predator hoverfly Eupeodes corollae detect and are attracted to EBF. Then, we found a neuron housed in type III basiconic sensilla of adult antenna responding to EBF. We further verified that in both adults and larvae odorant receptor EcorOR3 and odorant-binding protein EcorOBP15 mediate detection of EBF and structurally similar volatiles. Finally, we provide evidence that larvae of E. corollae may use aphid-derived EBF for prey location in the short-range, whereas adults could detect plant-derived EBF to find attacked plants from longer distances. Thus, while dissecting the molecular basis for attraction to EBF produced by two different sources, our results may find potential applications in integrated aphid management approaches.