Identification and characterization of the bombykal receptor in the hawkmoth <i>Manduca sexta</i>

Abstract

<i>Manduca sexta</i> females attract their mates with the release of a species-specific sex-pheromone blend, with bombykal (<i>E</i>,<i>Z</i>)-10,12-hexadecadienal and (<i>E</i>,<i>E</i>,<i>Z</i>)-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 <i>Xenopus</i> 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 <i>Bombyx mori</i> 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 (<i>E</i>,<i>E</i>,<i>Z</i>)-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.