The effects of topical application of various fatty acids on pheromone and glandular lipid biosynthesis in the moth Heliothis virescens

Abstract

Binary mixtures of deuterium-labeled palmitic acid and an excess of different fatty acids were applied to the sex pheromone gland of female Heliothis virescens and the effects on the terminal steps of pheromone biosynthesis, including incorporation of fatty acids into the glandular lipids, observed. Relative to labeled palmitic acid applied alone, application of all the binary mixtures resulted in decreased levels of the labeled pheromone component, ( Z)-11-hexadecenyl acetate (Z11-16:OAc), but there was generally no decrease in the amounts of labeled pheromone precursor, ( Z)-11-hexadecenoate, nor labeled palmitate in the glandular lipids. These data suggest that the excess of fatty acid in the gland inhibits Δ11-desaturation. However, in the case of excess myristoleic acid, the amount of labeled ( Z)-11-hexadecenoate increased significantly, suggesting that this acid inhibited fatty acid reduction. Dose–response tests with certain of the fatty acids were consistent with the above interpretations and further indicated that the gland had a high capacity for rapidly activating and incorporating excess fatty acids into the glandular lipids. Finally, application of the various fatty acids resulted in increased levels of these acids in the gland and, in the cases of myristoleic, palmitoleic and myristic acids, it also resulted in increased levels of the corresponding aldehydes, which had previously been detected in the gland of female H. virescens. This suggests that the fatty acid reductase in H. virescens is not highly specific for the major component, and that the final ratio of pheromone components is determined in part by the availability of their corresponding fatty acids in the gland.