Regulation Of Pheromone Biosynthesis Research Articles

Regulation of pheromone biosynthesis in the “Z strain” of the European corn borer, Ostrinia nubilalis

The regulation of pheromone biosynthesis by the neuropeptide PBAN in the Z strain of the European corn borer, Ostrinia nubilalis, was investigated using labeled intermediates. Injection of radiolabeled acetate showed PBAN did not influence the de novo synthesis of saturated fatty acids in the gland. When deuterium-labeled myristic acid was topically applied to the gland, females injected with PBAN produced more labeled pheromone than did control females, indicating that PBAN controls one of the later steps of pheromone biosynthesis. Although more myristic acid was Delta11-desaturated in the gland in the presence of PBAN, this was counterbalanced by less Delta11-desaturation of palmitic acid, indicating that desaturase activity did not change overall. This change in flux of myristic acid through to pheromone was shown to be caused by increased reduction of fatty acid pheromone precursors occurring in the presence of PBAN.

Evidence for two‐step regulation of pheromone biosynthesis by the pheromone biosynthesis‐activating neuropeptide in the moth Heliothis virescens

The control of pheromone biosynthesis by the neuropeptide PBAN was investigated in the moth Heliothis virescens. When decapitated females were injected with [2-(14)C] 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.

Insect semiochemical research in Korea: Overview and prospects

Rapid progress has been made in research on insect pheromones and other semiochemicals in Korea during the last two decades. Sex pheromone compositions have been identified in several major orchard and other horticultural moth pest species and some other species in Korea, such as Helicoverpa assulta, Grapholita molesta, Carposina sasakii, Adoxophyes orana, Lyonetia prunifoliella, Phyllonorycter ringoniella, Dichocrocis punctiferalis, Ostrinia furnacalis and Peridroma saucia. Some of these identified sex pheromones have already been successfully incorporated into IPM systems, and are now being used as direct and indirect pest control means in Korea. Korean populations of many of these species showed significant differences in pheromone compositions from those reported in the neighboring countries of Japan and China, suggesting that such interpopulational pheromone polymorphism is more common across the insect world than previously thought. Sex pheromone compositions were also identified in some aphid species in Korea such as Aphis spiraecola and Tuberocephalus momonis, and it was soon found that the aphid sex pheromone components were highly attractive to their predator lacewings. The presence of kairomones responsible for attracting egg parasitoids was shown in a pheromone component, hot pepper odor and male scale factor for H. assulta, and in male accessory glands for Lymantria dispar. Studies on the regulation of pheromone biosynthesis and release were carried out simultaneously in some species in Korea, resulting in the characterization of PBAN (pheromone biosynthesis activating neuropeptide) in H. assulta and Adoxophyes sp. A semiochemical research system has been firmly established in Korea through these studies. In some areas, successful monitoring and mating disruption technology have been effectively transferred from researchers to the end users in Korea, which will soon be expanded to wider areas. Continuous attempts to identify and use semiochemicals as well as wider applications of semiochemicals in pest control are expected in Korea in the coming years. Since Korean research on semiochemicals does not cover vast areas due to limited resources, focused research and practical application will be needed for selected target insect species.

Down regulation of pheromone biosynthesis: Cellular mechanisms of pheromonostatic responses

The biochemical second messenger system during pheromonotropic and pheromonostatic activities was assessed and compared. The involvement of G-proteins was implicated by the stimulatory action of sodium fluoride (NaF), at a range of 1–2 mM, on both pheromone biosynthesis and intracellular cAMP levels in isolated intersegmental membranes of Helicoverpa armigera. However, cholera toxin did not mimic the pheromonotropic response of PBAN. The stimulatory action of NaF was significantly inhibited by adrenergic agonists (tyramine and clonidine) as was observed at low levels of PBAN. At high levels of PBAN, although cAMP production was inhibited, pheromone biosynthesis was unaffected by clonidine. A similar phenomenon was observed with the ionophore, thapsigargin, in which adrenergic agonists did not inhibit pheromone biosynthesis but reduced intracellular cAMP to basal levels. Thus pheromonotropic activity exhibited both cAMP-independent and cAMP-dependent stimulatory responses. The calcium calmodulin inhibitor, W7, inhibited pheromone biosynthesis and intracellular cAMP production which was induced either by Hez-PBAN, NaF or thapsigargin. The pheromonostatic activity by clonidine was prevented in the presence of pertussis toxin, thereby indicating the involvement of inhibitory G-protein (G i) in the inhibitory action of adrenergic agonists on the activity of Hez-PBAN. From the results we hypothesized that negative regulation of pheromonotropic activity occurs at the membrane receptor level by the interaction of an adrenergic receptor.

Sex pheromone biosynthesis in the tortricid moth, Ctenopseustis herana (Felder & Rogenhofer)

Biosynthesis of the unusual sex pheromone component (Z)-5-tetradecenyl acetate (Z5-14:OAc) was studied in the tortricid moth, Ctenopseustis herana (Felder & Rogenhofer), by fatty acid methyl ester (FAME) analysis of the pheromone gland, and topical application of various deuterium-labelled acids to the gland. The only unusual unsaturated FAME found in base-methanolyzed glands of females was the putative precursor of the pheromone, methyl (Z)-5-tetra-decenoate (Z5-14:Me). When deuterium-labelled, myristic, palmitic, stearic, lauric, and oleic acids were applied to the gland, label was incorporated into the pheromone component only from the first three acids (i.e., Z5-14:OAc could not be biosynthesized from lauric or oleic acids). Furthermore, the amount of label incorporated from the first three acids decreased in the order myristic > palmitic > stearic. Application of labelled myristic acid to the gland resulted in incorporation of label into Z5-14:Me. These data are consistent with the biosynthesis of Z5-14:OAc in C. herana resulting from Δ5-desaturation of myristic acid, a novel biosynthetic route for a moth sex pheromone component. Regulation of pheromone biosynthesis in this species was also investigated. Decapitation of female C. herana resulted in a significant decline in sex pheromone titre. Injection of female head extract or synthetic Bombyx mori pheromone biosynthesis-activating neuropeptide (PBAN) into decapitated female C. herana gave a significant increase in pheromone titre, suggesting that pheromone biosynthesis in this species is regulated by a PBAN or PBAN-like substance. © 1996 Wiley-Liss, Inc.

Sex pheromone biosynthesis in the tortricid moth,Ctenopseustis herana (Felder & Rogenhofer)

Biosynthesis of the unusual sex pheromone component (Z)-5-tetradecenyl acetate (Z5-14:OAc) was studied in the tortricid moth, Ctenopseustis herana (Felder & Rogenhofer), by fatty acid methyl ester (FAME) analysis of the pheromone gland, and topical application of various deuterium-labelled acids to the gland. The only unusual unsaturated FAME found in base-methanolyzed glands of females was the putative precursor of the pheromone, methyl (Z)-5-tetra-decenoate (Z5-14:Me). When deuterium-labelled, myristic, palmitic, stearic, lauric, and oleic acids were applied to the gland, label was incorporated into the pheromone component only from the first three acids (i.e., Z5-14:OAc could not be biosynthesized from lauric or oleic acids). Furthermore, the amount of label incorporated from the first three acids decreased in the order myristic > palmitic > stearic. Application of labelled myristic acid to the gland resulted in incorporation of label into Z5-14:Me. These data are consistent with the biosynthesis of Z5-14:OAc in C. herana resulting from Δ5-desaturation of myristic acid, a novel biosynthetic route for a moth sex pheromone component. Regulation of pheromone biosynthesis in this species was also investigated. Decapitation of female C. herana resulted in a significant decline in sex pheromone titre. Injection of female head extract or synthetic Bombyx mori pheromone biosynthesis-activating neuropeptide (PBAN) into decapitated female C. herana gave a significant increase in pheromone titre, suggesting that pheromone biosynthesis in this species is regulated by a PBAN or PBAN-like substance. © 1996 Wiley-Liss, Inc.

Neural regulation of sex-pheromone glands in Lepidoptera

Substantial progress has been made toward understanding the neuroendocrine regulation of sex-pheromone glands in Lepidoptera, but several recent studies have revealed that direct contact of the pheromone gland with blood-borne factors is not necessary to induce pheromone biosynthesis and release in some species. The nervous system provides an alternate route of activation. Evidence from several species indicates that the pheromone gland is innervated and regulated by neural activity. Electrical stimulation of efferent axons arising from the terminal abdominal ganglion results in a significant increase in pheromone production, and neural stimulation furthermore evokes the rapid release of pheromone into the surrounding air. In some heliothine moths, the biogenic monoamine octopamine stimulates pheromone production, and octopamine has also been isolated from pheromone gland tissue. Moreover, the critical period for maximal octopamine action mirrors the time when peak levels of octopamine are present in the gland. These findings suggest that octopamine is involved in the regulation of pheromone biosynthesis and/or release, but its actions depend on additional factors associated with age and photoperiod. The combined evidence using anatomical, electrophysiological, and biochemical methods indicates that the pheromone gland is innervated and regulated by neurons that arise in the terminal abdominal ganglion. Indirect evidence suggests that at least some of this innervation is octopaminergic. In these respects, the pheromone gland in Lepidoptera exhibits characteristics of other neuroeffector systems in insects.

Regulation of pheromone biosynthesis by a brain hormone in two moth species

Experiments were performed to characterize the action of a brain hormone on pheromone biosynthesis in female redbanded leafroller and cabbage looper moths. Results showed that the two species differed in their respective control mechanisms. In the cabbage looper, pheromone titer from decapitated females that received either saline or brain extract injections was not significantly different from control females, suggesting that pheromone biosynthesis was not dependent on the presence of the brain hormone. In contrast, with redbanded leafroller females, studies using radiolabeled acetate incorporation as well as incorporation of deuterium-labeled hexadecanoic acid showed that (i) the brain hormone was required for pheromone biosynthesis, (ii) the brain hormone regulated pheromone biosynthesis by activating synthesis of octadecanoyl and hexadecanoyl intermediates, and (iii) the brain hormone did not control other enzymes in the pathway. Regulation of fatty acid synthetase was unlikely since assays of the enzyme from decapitated and normal females showed no differences in the amount or distribution of the 18- and 16-carbon acyl end products. These results in conjunction with those from organ cultures of the pheromone gland suggest that the brain hormone acts by increasing the substrate supply for fatty acid synthesis.

Biosynthesis of the acetate ester precursor of the spruce budworm sex pheromone by an acetyl CoA: Fatty alcohol acetyltransferase

The biosynthesis of 11-tetradecenyl acetate, the major storage precursor of the aldehyde pheromone of Choristoneura fumiferana, the eastern spruce budworm, has been found to be catalyzed by an acetyl-CoA: fatty alcohol acetyltransferase. In vitro, acetyltransferase activity was found almost exclusively in extracts from the pheromone producing gland, and could be demonstrated in vivo by topical application of [ 14C]tetradecanol to the glands. Moreover, the activity was under developmental regulation, being low before and immediately after emergence of the moths from the pupal stage, and rising to a maximum in concert with the increase in glandular pheromone levels. Maximum activity with saturated alcohols was observed for acceptors of 12 to 15 carbons in chain length, with higher activities being found for the cis or trans monounsaturated analogs. The specificity of this enzyme with respect to substrate, morphological location and developmental regulation, indicates that it plays a key role in regulation of pheromone biosynthesis.