Regulation Pheromone biosynthesis

Fig. (7) shows pheromone biosynthesis regulated by JH in production of a number of cockroach and beetle species [80-84]. 20-... 

Abstract Pheromones are utilized by many insects in a complex chemical communication system. This review will look at the biosynthesis of sex and aggregation pheromones in the model insects, moths, flies, cockroaches, and beetles. The biosynthetic pathways involve altered pathways of normal metabolism of fatty acids and isoprenoids. Endocrine regulation of the biosynthetic pathways will also be reviewed for the model insects. A neuropeptide named pheromone biosynthesis activating neuropeptide regulates sex pheromone biosynthesis in moths. Juvenile hormone regulates pheromone production in the beetles and cockroaches, while 20-hydroxyecdysone regulates pheromone production in the flies. 

The role of the nervous system in pheromone biosynthesis in moths is not clearly understood. Christensen and co-workers [208-211] proposed that the neurotransmitter octopamine may be involved as an intermediate messenger during the stimulation of sex pheromone production in H. virescens. These workers suggested that octopamine was involved in the regulation of pheromone production and that PBAN s role lies in the stimulation of octopamine release at nerve endings. However, contradicting results concerning octopa-mine-stimulated pheromone production were reported in the same species as well as other moth species [163,172,212-214]. 

Additional evidence came from the finding that sex pheromone production could be stimulated in male houseflies that do not normally produce detectable sex pheromone components. Male houseflies were found to have longer chain alkenes, Z9-27 H,but did not have Z9-23 H. Implantation of ovaries into male houseflies resulted in a change in hydrocarbon biosynthesis such that the longer chain alkenes were not made but rather they produced the shorter chain length Z9-23 H [240]. Likewise, injection of 20-hydroxyecdysone into males induced sex pheromone production in a dose-dependent manner. These studies demonstrated that males possess the biosynthetic capability to produce sex pheromone, but normally do not produce the 20-hydroxyecdysone necessary to induce sex pheromone production. Males became an excellent model in which to study the hormonal regulation of pheromone biosynthesis in the housefly. 

In moths, it was discovered in Helicoverpa zea that a peptide produced in the subesophageal ganglion portion of the brain complex regulates pheromone production in female moths (19). This factor has been purified and characterized in three species, Helicoverpa zea (20), Bombyx mori (21, 22), and Lymantria dispar (23). They are all a 33- or 34-amino acid peptide (named pheromone biosynthesis activating neuropeptide, PBAN) and have in common an amidated C-terminal 5-amino acid sequence (FXPRL-amide), which is the minimum peptide fragment required for pheromon-tropic activity. In the redbanded leafroller moth, it was shown that PBAN from the brain stimulates the release of a different peptide from the bursae copulatrix that is used to stimulate pheromone production in the pheromone gland found at the posterior tip of the abdomen (24). 

Schal, C., Fan, Y. and Blomquist, G. J. (2003). Regulation of pheromone biosynthesis, transport, and emission in cockroaches. In Insect Pheromones Biochemistry and Molecular Biology, eds. G. J. Blomquist and R. Vogt, pp. 283-322. New York Academic Press. 

Boppre, M. and Schneider, D. (1985). Pyrrolizidine alkaloids quantitatively regulate both scent organ morphogenesis and pheromone biosynthesis in male Creatonotos moths (Lepidoptera Arctiidae). Journal of Comparative Physiology A 157 569-577. 

In no model pheromone biosynthetic system is the molecular mechanism of hormonal regulation completely understood. The mechanism of action of JH and the nature of its receptor remain one of the mysteries of insect science, and the clear-cut action of JH by itself in inducing specific genes in pheromone production in bark beetles offers an excellent model for study. A better understanding of the PBAN receptor and the second messenger system it triggers as well as the steps regulated in pheromone biosynthesis is also needed. The next several years should see some of the key questions answered in model insects. 

This book is designed as a sourcebook for the next decade of research, and we hope it fills this expectation. Chapters have been assembled from experts who are at the frontiers of pheromone physiology, biochemistry, morphology, neurobiology and molecular biology. Ultimately, just as behavioral chemicals themselves have been extended to pest management, research on pheromone biosynthesis, hormonal regulation and reception may be directed toward application and ultimately used in insect control. 

Another technique that is utilized to help ensure that label is incorporated into the pheromone is to apply the precursor at the same time as pheromone biosynthesis activating neuropeptide (PBAN). PBAN is a peptide hormone that regulates pheromone biosynthesis in most, but not all, moths. So, first it must be demonstrated that PBAN regulates pheromone production. In the case of the cabbage looper,... 

Zhu J. W., Zhao C. H., Lu F., Bengtsson M. and Lofstedt C. (1996) Reductase specificity and the ratio regulation of E/Z isomers in pheromone biosynthesis of the European corn borer, Ostrinia nubilalis (Lepidoptera Pyralidae). Insect Biochem. Mol. Biol. 26, 171-176. 

PBAN regulation of pheromone biosynthesis in female moths... 

In this chapter we will review the current state of knowledge about how pheromone production is regulated in female moths. Discussion of PBAN identification and localization within the nervous system will be followed by how PBAN acts to stimulate pheromone biosynthesis. The final major topic will be a discussion of mediators and inhibitors of PBAN action. A considerable amount of information has accumulated with regard to regulation of pheromone biosynthesis in moths since Pheromone Biochemistry (Prestwich and Blomquist, 1987) was first published, and this chapter is not all inclusive. Further information can also be obtained in several reviews (Raina, 1993 Jurenka, 1996 Teal et al., 1996 Rafaeli et al., 1997b Raina, 1997 Rafaeli, 2002). 

Once it was established that pheromone biosynthesis was regulated by a peptide produced in the SEG, the next goal was to identify the peptide. In the purification of any biologically active factor, each purification step requires a sensitive bioassay to measure the active material. In the purification of PBAN, the bioassay consisted of head ligated females that were injected with bioactive fractions. After a 1-3 h period of incubation, the pheromone gland was excised and titers of pheromone determined by gas chromatography (GC). The first PBAN was purified and identified from H. zea (Raina el ah, 1989). Dissection of about 5000 brain-SEG complexes followed by several steps of HPLC purification resulted in a pure peptide that could be sequenced. It was found to be a 33 amino acid peptide with a C-terminal amide (Table 5.1). The peptide was synthesized and was shown to be active in the bioassay in a dose as low as 2 pmol (Raina et al., 1989). In the same year, a PBAN from B. mori was purified and sequenced (Kitamura et al.,... 

Arima R., Takahara K., Kadoshima T., Numazaki F., Ando T., Uchiyama M., Nagasawa H., KitamuraA. and Suzuki A. (1991) Hormonal regulation of pheromone biosynthesis in the silkworm moth, Bombyx mori (Lepidoptera Bombycidae). Appl. Entomol. Zool. 26, 137-147. 

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