Identification and characterization of the bombykal receptor in the hawkmoth Manduca sexta

Manduca sexta females attract their mates with the release of a species-specific sex-pheromone blend, with bombykal (E,Z)-10,12-hexadecadienal and (E,E,Z)-10,12,14-hexadecatrienal being the two major components. Here, we searched for the hawkmoth bombykal receptor in heterologous expression systems. The putative pheromone receptor MsexOr1 coexpressed with MsexOrco in Xenopus oocytes elicited dose-dependent inward currents upon bombykal application (10-300 μmol l^-1), and coexpressed in HEK293 and CHO cells caused bombykal-dependent increases in the intracellular free Ca²⁺ concentration. In addition, the bombykal receptor of Bombyx mori BmOr3 coexpressed with MsexOrco responded to bombykal (30-100 μmol l^-1) with inward currents. In contrast, MsexOr4 coexpressed with MsexOrco responded neither to bombykal (30-100 μmol l^-1) nor to the (E,E,Z)-10,12,14-hexadecatrienal mimic. Thus, MsexOr1, but not MsexOrco and probably not MsexOr4, is the bombykal-binding pheromone receptor in the hawkmoth. Finally, we obtained evidence that phospholipase C and protein kinase C activity are involved in the hawkmoth's bombykal-receptor-mediated Ca²⁺ signals in HEK293 and CHO cells.