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

Abstract

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 (ii) 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 ofthe 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.Recent research in moths has greatly advanced our understanding of the endogenous control mechanisms responsible for sex pheromone production and release. Female moths emit pheromone only when they call, a behavior that requires input from the brain or other higher nervous centers (1-4). Production of pheromone, on the other hand, is under neuroendocrine control by a peptide localized in the subesophageal ganglion portion of the brain complex (5-7).Several lines of evidence support the existence of a brain hormone that controls pheromone production. After neckligation or decapitation, females exhibited a decrease in pheromone titer (5, 6). A subsequent increase in titer was induced by injection of brain extract. Since hemolymph showed pheromonotropic activity only during periods when a female was producing pheromone, it was concluded that control of pheromone production was mediated by release of the brain hormone into the hemolymph at specific times of the day (5). The presence of functionally similar pheromonotropic factors in several families of moths has been demonstrated (5, 7) as well as from brains of insects from other orders-e.g., a cockroach, Periplaneta americana, and a cricket, Gryllus bimaculatus (L.S. and W.L.R., unpublished results).The biosynthetic pathways ofpheromone production for the two species examined in the present study, the redbanded leafroller moth (RBLR), Argyrotaenia velutinana, and the cabbage looper moth (CL), Trichoplusia ni, are depicted in

Innervation and neural regulation of the sex pheromone gland in female Heliothis moths.

“…In repeated trials, neither octopamine nor PBAN induced consistent, significant increases in pheromone levels in H. virescens or H. zea females under our experimental conditions. This may be due to the absence of a tissue such as fat body that provides pheromone precursors to the PG (18).…”

“…Although it is clear that pheromone production is not controlled by the same mechanisms in all species, a major development was the demonstration that pheromone biosynthesis in certain species of moths can be stimulated by the injection of brain homogenates into intact females (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). Two structurally related pheromone biosynthesis activating neuropeptides (PBANs) were isolated and identified from homogenates of brains and subesophageal ganglia from the corn earworm moth Helicoverpa zea (formerly Heliothis zea and abbreviated H. zea in this report; see refs.…”

Stimulation of pheromone biosynthesis in the moth Helicoverpa zea: action of a brain hormone on pheromone glands involves Ca2+ and cAMP as second messengers.

“…However, there is no evidence to suggest PBAN control of pheromone production in female gypsy moths (R. E. Charlton and W.L.R., unpublished results), and another mechanism is probably acting to control pheromone biosynthesis. Other mechanisms implicated in the control ofpheromone biosynthesis in other moths include juvenile hormone control of PBAN release in a migratory moth, Psuedaletia unipuncta (14), and the apparent lack of PBAN control in the cabbage looper, Trichoplusia ni (15). In the latter case there is evidence for ecdysone regulation of gland competency during the pupal stage (16).…”

Molecular cloning of the pheromone biosynthesis-activating neuropeptide in Helicoverpa zea.

“…The pheromone biosynthesis-activating neuropeptide (PBAN) of the corn earworm Helicoverpa (Heliothis) zea, Hez-PBAN, is a 33-amino acid neurohormone that controls sex pheromone biosynthesis in females of many species of moths (1)(2)(3)(4)(5)(6)(7)(8). The amino acid sequence of Hez-PBAN is as follows: Leu-Ser-Asp-Asp-Met-Pro-Ala-Thr-Pro-Ala-AspGln-Glu-Met-Tyr-Arg-Gln-Asp-Pro-Glu-Gln-Ile-Asp-SerArg-Thr-Lys-Tyr-Phe-Ser-Pro-Arg-Leu-NH2.…”