Pheromone biosynthesis males

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. 

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. 

Figure 6.16 Model illustrating interspecific regulatory differences in an early-stage reaction in isoprenoid pheromone biosynthesis between male Ips paraconfusus Lanier and Ips pini (Say). Feeding on host phloem results in synthesis of the full amount of the major pheromone component and full activity of HMG-R for both species. The impact of feeding on HMG-R transcript levels is yet to be determined. Topical treatment of male I. pini with JH III mimics feeding nearly completely in terms of pheromone mass and HMG-R activity. Topical treatment of male I. paraconfusus with JH III does not mimic feeding in terms of pheromone mass or HMG-R activity. Topical treatment of both species with JH III results in significantly enhanced levels of HMG-R transcript. One hypothetical explanation for the interspecific difference is that a second hormone (SH) or factor may be associated with the synthesis, stability, and/or activity of HMG-R in I. paraconfusus.

Wiygul et al. (1982) reported the site of pheromone biosynthesis in male boll weevils as the fat body. To date this is the only insect where the fat body has been proposed as a site for pheromone biosynthesis, and it is an obvious contradiction that in most species of the closely related Scolytidae, isoprenoid pheromone biosynthesis has been reported to occur in the alimentary canal (see section 6.6.2). Wiygul et al. (1982) observed that the level of pheromone production... 

Tittiger C., Blomquist G. J., Ivarsson P., Borgeson C. E. and Seybold S. J. (1999) Juvenile hormone regulation of HMG-R gene expression in the bark beetle, Ips paraconfusus (Coleoptera Scolytidae) implications for male aggregation pheromone biosynthesis. Cell. Mol. Life Sci. 55, 121-127. 

Coleoptera Scolytidae) implications for male aggregation pheromone biosynthesis. Cell. Mol. Life Sci. 55, 121-127. 

Table 4.5 Number of transcripts reported for some elongase genes probably involved in pheromone biosynthesis. The cytological localization (cyt) of the genes is reported. Relative male vs. female expression is indicated (Parisi et al., 2004 Mackay et al., 2005).

Pheromone production in females of many species of moths is controlled by a hormone, the pheromone biosynthesis activating neuropeptide (PBAN). PBAN was isolated from Helicoverpa Heliothls ) zea and identified as a 33 amino acid peptide. Amidation of the C-terminus is important for the biological activity of this hormone. Oxidation of two Met residues at postitions 5 and 14 enhanced pheromonotropic activity of PBAN. Stability of PBAN in saline can be increased by the substitution of Nle for Met at positions 5 and 14. Biological activity is mostly associated with brain-suboesophageal ganglion and corpora cardiaca of both female and male moths. Terminal abdominal ganglion does not appear to be directly involved in the control of pheromone production. PBAN is slowly degraded in hemolymph. Future possibilities of research on PBAN are discussed. 

Evidence accumulated for and against the paradigm that bark beetle pheromone biosynthesis involved direct modification of host precursor monoterpenes. For 1. pini, the issue was laid to rest with the demonstration that male tissues incorporate radio-labeled acetate into ipsdienol in a manner consistent with pheromone production. Similar experiments proved the de novo biosynthesis of frontalin, an important isoprenoid-derived semiochemical produced by male Dendroctonus jeffreyi It is probable that other Coleoptera can also synthesize monoterpenes, either as pheromone components " or defensive compounds. Despite the capacity for de novo biosynthesis, plant precursor modification is likely an important source of pheromone components for some species. In these cases, plant chemicals could enter the pheromone biosynthetic pathway at later steps. 

Reproductive Behavior. Male accessory glands contain peptides which affect female reproductive behavior. Female sexual receptivity is diminished after mating (22) and oviposition is stimulated (22). Peptides responsible for these behaviors have been isolated from Drosophila species (22,23) and sequenced. In addition, a peptide with similar behavioral influences in a lepidopteran has been isolated from Helicoverpa zea (24). Miller (this volume) discusses the potential of these "sex peptides" in the development of unique insect control strategies. While males influence female reproductive behavior via the action of "sex peptides", females, especially in the Lepidop-tera, influence male behavior through the release of pheromone. The production of pheromone, in turn, is controlled by the pheromone biosynthesis activating neuropeptide (PBAN for a comprehensive review see 25). PBAN-like activity has been observed in more than 20 insect species (25) and offers another avenue for exploitation of neuropeptides in insect control. 

Macrolide aggregation pheromones produced by male cucujid beetles are derived from fatty acids. Feeding experiments with labeled oleic, linoleic, and palmitic acids indicate incorporation into the macrolide pheromone component [ 117 ]. The biosynthesis of another group of beetle pheromones, the lactones, involves fatty acid biosynthetic pathways. Japonilure and buibuilactone biosynthesized by the female scarab, Anomalajaponica, involves A9 desaturation of 16 and 18 carbon fatty acids to produce Z9-16 CoA and Z9-18 CoA,hydroxylation at carbon 8 followed by two rounds of limited chain shortening and cyclization to the lactone [118]. The hydroxylation step appears to be stereospecific [118]. 

Some male arctiid moths produce their courtship pheromone from dietary pyrrolizidine alkaloids acquired during feeding by the larvae [ 126]. Conversion of monocrotaline to hydroxydanaidal by males is accomplished by aromatiza-tion, ester hydrolysis and oxidation of an alcohol to the aldehyde [7]. In the case of Utetheisa ornatirx the stereo-configuration at C7 of the dietary alkaloid is the same as the pheromone released (R). In contrast, another arctiid, Creatono-tos transiens, can convert a dietary precursor alkaloid with the (S) configuration at C7 (heliotrine) to (l )-hydroxydanaidal. The biosynthesis occurs by first oxidation-reduction at C7 to convert the stereochemistry and then proceeds through aromatization, hydrolysis, and oxidation [7]. 

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