Neural regulation of sex pheromone biosynthesis in Heliothis moths

Abstract

Pheromone biosynthesis in females of Heliothis zea is regulated endogenously by a neuropeptide produced in the subesophageal ganglion. We have found that the ventral nerve cord must be intact for normal induction of pheromone biosynthesis and that pheromonotropic activity is associated with extracts of the abdominal nerve cord, but only during the period when pheromone is produced. We did not find evidence of pheromonotropic activity in hemolymph obtained from females that were producing pheromone. Extracts of the brain-subesophageal ganglion complex, which contain pheromone biosynthesis activating neuropeptide (PBAN), induced pheromone biosynthesis when applied to the terminal abdominal ganglion only if nerves from this ganglion to the pheromone gland were intact. Brain-subesophageal ganglion extracts did not induce biosynthesis when applied directly to the pheromone glands in vitro. From our results, we conclude that the target site of PBAN is not the pheromone gland but the terminal abdominal ganglion, and we hypothesize that the abdominal nerve cord transports PBAN to the terminal abdominal ganglion.Endogenous regulation of reproductive physiology and behavior associated with pheromone production and release in many insects results from the action of nervous, neuroendocrine, and/or endocrine stimulation (1-4). However, while the chemistry and biological effects of sex pheromones are understood more fully for moth species than for other groups of insects (5), the endogenous mechanisms that regulate the initiation and inhibition of pheromone biosynthesis by moths remain largely unexplored. Neural, neurohormonal, and hormonal regulators effectively control the periodicity of sexual signaling and are thus of prime importance for the reproductive success of moth species. Although these processes are tightly coordinated, no single neural, neuroendocrine, or endocrine factor regulates the complete system. In fact, there are conflicting reports (6-11) regarding the endogenous mechanisms that control even a single aspect of the pheromone communication system in moths: induction of pheromone biosynthesis.Studies on the corn earworm moth Heliothis zea (6-8) have firmly established that injection of extracts of the subesophageal ganglion induces pheromone biosynthesis. It was hypothesized that the neuropeptide responsible, pheromone biosynthesis activating neuropeptide (PBAN), was released from the corpora cardiaca, carried in the hemolymph, and acted directly on the cells of the pheromone gland (4, 6). However, gypsy moths, which also produce PBAN (6), do not require either the corpora allata or corpora cardiaca for production and release of the sex pheromone but do require that the ventral nerve cord be intact for production and release of normal amounts of pheromone (9-11). Thus, in this case neural rather than hormonal factors appear to be the main components regulating biosynthesis.These apparent discrepancies in the regulation of pheromone production caused us to investigate the mechanism by which PBAN ind...

The loss of female sex pheromone after mating in the corn earworm moth Helicoverpa zea: identification of a male pheromonostatic peptide.

“…While this Mating may shut off the release of pheromonotropic peptides, either into the hemolymph or from presumptive release sites in the VNC (19). An intact VNC was previously reported to be essential for pheromone production in H. zea (20); we found, however, that there was no apparent diminution of the pheromone present in the VNC-transected virgins (Fig. 6) (20).…”

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

“…Isolated glands (abdominal segments 8 and 9) of H. zea and H. armigera were also stimulated to produce pheromone when incubated with a brain homogenate or with synthetic PBAN (17)(18)(19). However, Teal et al (9) reported that isolated pheromone glands of H. zea were not stimulated by PBAN and presented evidence that intact nerves leading from the TAG are required for PBAN activity. They suggested that a second neurosecretory substance released from the TAG actually stimulated the pheromone gland.…”

“…One hypothesis suggests that PBAN is synthesized in the SEG, transported to the corpora cardiaca, and then released into the hemolymph, where it can act on the pheromone gland to induce pheromone biosynthesis (8). The second hypothesis suggests that PBAN is transported from the SEG through the ventral nerve chord (VNC) to the terminal abdominal ganglia (TAG), and then another neurosecretory substance acts on the pheromone gland to induce pheromone production (9). A recent study reported that the pheromone gland is innervated and that the biogenic amine octopamine stimulates pheromone production, suggesting neural regulation of pheromone biosynthesis (10).…”

Introgressing Pheromone QTL Between Species: Towards an Evolutionary Understanding of Differentiation in Sexual Communication

“…However, acetate esters can be converted back to the corresponding alcohols through acetate esterase (Figure 1). Teal et al (1989) found significantly higher acetate esterase activity in Hv pheromone glands, suggesting that any acetate esters produced by Hv would be immediately converted back to the corresponding alcohols. Thus, an alternative explanation for the differences between Hv and Hs might involve the presence or activity of acetate esterase.…”