Hormonal regulation of sex pheromone biosynthesis in the turnip moth, Agrotis segetum

Abstract

Pheromone production in the female turnip moth, Agrotis segetum, is under the control of a brain factor. This factor was demonstrated to be a proteinaceous substance termed pheromone biosynthesis activating neuropeptide-like substance (PBAN-like substance). The sex pheromone of Swedish A. segetum includes (d-5-decenyl acetate, (d-7-dodecenyl acetate, and (a-9-tetradecenyl acetate as major components. Decapitation of a female decreased pheromone production significantly. Pheromone production was restored by injection of homogenates of either male or female brain-suboesophageal ganglion or the corpora cardiaca alone. Pheromonotropic activity was also found in homogenates of the female thoracic ganglion and abdominal ganglion that were obtained during scotophase. Injection of female brain and thoracic ganglion homogenates made from insects during the scotophase induced two and four times as much 27-1 2:OAc, respectively, as injection with similar homogenates from photophase. As little as one-eighth female equivalent (FE) brain homogenate was sufficient to increase the amount of Z7-12:OAc. The effect of brain homogenate on pheromone titer reached its maximum after 30 min. The activity of the PBAN-like substance present in female brain extracts was not correlated to the age of the donor. Injection of hemolymph collected during either photophase or scotophase into decapitated females did not increase the pheromone titer. The target site of the PBAN-like substance was not the pheromone gland, and the ventral nerve cord was not involved in the transportation of the PBAN-like substance, which implies a mode of action different from what has been reported in other moths. Brain homogenates obtained during photophase from females of African A. segetum, Spodoptera littoralis, or Ostrinia nubilalis as well as synthetic Bombyx-PBAN also induced pheromone production in de-

Physiological control of pheromone production inChoristoneura fumiferana andC. Rosaceana

“…Such hormonal cross-reactivity has been reported for several other lepidopteran species (Raina et al, 1987;Rafaeli and Soroker, 1989;Qiu and Cao, 1989;Gazit et al, 1992;Picimbon et al, 1995;Zhu et al, 1995). Interestingly, the level of pheromonotropic activity did not differ between intra-and inter-Br-SEG treatments, probably because both species are of similar size (Raina et al, 1987) and/or their brain factors are structurally very similar (Gazit et al, 1992).…”

Endogenous control of circadian rhythms of pheromone production in the turnip moth, Agrotis segetum

“…The pheromonotropic activity in hemolymph in A. segetum was much lower than that in Br-SOG or VNC. Zhu et al (1995) did not find any pheromonotropic activity in hemolymph in the scotophase. In the present study, a low but significant pheromonotropic activity was detected in the hemolymph during the scotophase.…”

“…Furthermore, pheromonotropic activity was detected in both hemolymph and VNC at certain photoperiod in the present study. Zhu et al (1995) also showed that severing VNC had no effect on the PBAN-induced pheromone production by injecting Br-SOG homogenates into decapitated female turnip moths. However, neither Zhu et al (1995) nor the present study observed any significant pheromone production when isolated pheromone glands were incubated with PBAN.…”

“…It has been demonstrated that a PBAN-like substance is involved in the control of sex pheromone production in A. segetum (Zhu et al, 1995). If PBAN is involved in the circadian regulation of pheromone production, PBAN-like activity itself must exhibit a circadian rhythm.…”

Regulation of sex pheromone biosynthesis in two noctuid species,S. littoralis andM. brassicae, may involve both PBAN and the ventral nerve cord

“…Other experiments aimed at determining the role of the VNC on pheromone production involve injection of PBAN into whole females or incubation with PBAN of isolated abdomens either intact or devoid of the VNC and the TAG (Jacquin et al, 1994;Jurenka et al, 1991;Ramaswamy et al, 1995;Teal et al, 1989;Zhu et al, 1995). As indicated above, when the abdomen incubation bioassay was performed with S. littoralis, it became clear, in agreement with all cases previously described in other species, including M. brassicae (Jacquin et al, 1994;Jurenka et al, 1991;Teal et al, 1989;Zhu et al, 1995), that PBAN stimulated pheromone production in the absence of the VNC and the TAG.…”