HORMONAL-REGULATION OF PHEROMONE BIOSYNTHESIS IN THE SILKWORM MOTH, BOMBYX-MORI (LEPIDOPTERA, BOMBYCIDAE)

In the silkworm moth (Bombyx mori L.), the sex pheromone [bombykol, (10E, 12Z)-10, 12-hexadecadien-1-ol] became undetectable 24 hr after decapitation, but its production was restored by the injection of a brain hormone (pheromone biosynthesis activating neuropeptide, PBAN). In order to understand the mode of action of this hormone, C-14-incorporation into pheromone precursors and related compounds was examined by treating the pheromone glands of normal, decapitated, and decapitated and hormone-injected virgin females with C-14-hexadecanoic acid. In the decapitated female moth, conversion of the C-14-acid into bombykol as well as other C16-fatty alcohols was very low. The levels of C-14-incorporation observed in normal females were partially recovered in the decapitated female by hormone injection. However, the amount of unsaturated C16-fatty acyl moieties and their levels of C-14-incorporation was not decreased as much by decapitation. This suggests that the main regulatory role of PBAN is in the reduction of an acyl moiety in the bombykol biosynthetic pathway rather than effecting unsaturation steps. Further, when the gland, which was removed from the decapitated female, was incubated in a Grace's medium with PBAN, the pheromone was again produced indicating the direct regulation of the pheromone gland by this hormone.