Submitted to: Archives of Insect Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/2006
Publication Date: 3/1/2007
Citation: Eltahlawy, H., Buckner, J.S., Foster, S.P. 2007. Evidence for two-step regulation of pheromone biosynthesis by the pheromone biosynthesis-activating neuropeptide in the moth Heliothis virescens. Archives of Insect Biochemistry and Physiology. 64(3):120-130. Interpretive Summary: Sexual communication in moths is mediated mainly by sex pheromones, which are volatile compounds used by female moths to attract potential mates from long distances. Most moth sex pheromone compounds are derived from fatty acids. The female makes sex pheromone in a specialized gland, near the tip of the abdomen. Sex pheromone production in many moths is under the control of a pheromone biosynthesis activating neuropeptide (PBAN), a hormone produced in the brain. PBAN works by affecting one or more enzymatic steps in the pheromone biosynthetic pathway. The control of pheromone biosynthesis by PBAN was investigated in the moth, Heliothis virescens, using labeled fatty acid precursors. When decapitated females were injected with [2-14C] acetate, females co-injected with PBAN produced significantly greater quantities of radiolabeled fatty acids in their pheromone glands than females co-injected with saline. The results indicate that PBAN controls an enzyme involved in the synthesis of fatty acids, probably acetyl-CoA carboxylase. Additional experiments using labeled fatty acid precursors of the H. virescens sex pheromone and proper controls indicated that PBAN also controls a later step in pheromone biosynthesis. The control by PBAN of two enzymes, near the beginning and end of the biosynthetic process, would seem to allow for more efficient utilization of fatty acids and pheromone.
Technical Abstract: The control of pheromone biosynthesis by the neuropeptide PBAN was investigated in the moth Heliothis virescens. When decapitated females were injected with [2-14C] acetate, females co-injected with PBAN produced significantly greater quantities of radiolabeled fatty acids in their pheromone gland than females co-injected with saline. This indicates that PBAN controls an enzyme involved in the synthesis of fatty acids, probably acetyl CoA carboxylase. Decapitated females injected with PBAN showed a rapid increase in native pheromone, and a slower increase in the pheromone precursor, (Z)-11-hexadecenoate. Total native palmitate and stearate (both pheromone intermediates) showed a significant decrease after PBAN injection, before their titers were later restored to initial levels. In contrast, the acyl-CoA thioesters of these two saturated fatty acids increased during the period when their total titers decreased. When a mixture of labeled palmitic and heptadecanoic (an acid that cannot be converted to pheromone) acids was applied to the gland, PBAN-injected females produced greater quantities of labeled pheromone and precursor than did saline-injected ones. The two acids showed similar time-course patterns, with no difference in total titers of each of the respective acids between saline- and PBAN-injected females. When labeled heptadecanoic acid was applied to the gland alone, there was no difference in titers of either total heptadecanoate or of heptadecanoyl-CoA between PBAN- and saline-injected females, suggesting that PBAN does not directly control the storage or liberation of fatty acids in the gland, at least for this fatty acid. Overall, these data indicate that PBAN also controls a later step involved in pheromone biosynthesis, perhaps the reduction of acyl-CoA moieties. The control by PBAN of two enzymes, near the beginning and end of the pheromone biosynthetic process, would seem to allow for more efficient utilization of fatty acids and pheromone than control of only one enzyme.