Paraconfusus pheromone biosynthesis

Byers J. A. (1981) Pheromone biosynthesis in the bark beetle, Ips paraconfusus, during feeding or exposure to vapours of host plant precursors. Insect Biochem. 11, 563-569. 

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.

Lu F. (1999) Origin and endocrine regulation of pheromone biosynthesis in the pine bark beetles, Ips pini (Say) and Ips paraconfusus Lanier (Coleoptera Scolytidae). PhD thesis. Univ. of Reno, Nevada, 152 pp. 

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. 

JH III is sufficient to induce pheromone biosynthesis in starved I. pini and D. jeffreyi, suggesting a relatively simple endocrine regulation. However, starved I. paraconfusus cannot be induced to synthesize pheromone by JH III, despite the fact that HMG-R expression rises with JH III treatment. Pheromone biosynthesis in I. paraconfusus requires feeding (Seybold et al., 2000 Tillman et al., in preparation). Since HMG-R expression is apparently regulated similarly in both species, I. paraconfusus must require an additional signal in order to activate pheromone biosynthesis. The necessary factors are likely to act post-transcriptionally or post-translationally on HMG-R. These studies show that extending information from one species to another must be done with caution, as even closely related bark beetles seem to have very different regulatory schema. 

HUGHES, P.R., RENWICK, A.A., Neural and hormonal control of pheromone biosynthesis in the bark beetle, Ips paraconfusus. Physiol. Entomol., 1977, 2, 117-123. 

Seybold S. J., Quilici D. R., Tillman J. A., Vanderwel D., Wood D. L. and Blomquist G. J. (1995) De novo biosynthesis of the aggregation pheromone components ipsenol and ipsdienol by the pine bark beetles Ips paraconfusus Lanier and Ipspini (Say) (Coleoptera Scolytidae). Proc. Natl. Acad. Sci. USA 92, 8393-8397. 

QUILICI, D.R., De novo biosynthesis of aggregation pheromone components by the pine bark beetles, Ips paraconfusus (Lanier) and Ips pini (Say) (Coleoptera Scolytidae), and identification of an interruptant and a synergist produced by Ips pini., Ph.D., 1997, University of Nevada, Reno. 

Fig. 12.3 Biosynthesis of the components of the aggregation pheromone of Ips paraconfusus by simple conversion from the host tree terpenes myrcene and a-pinene.

This chapter has described what has been learned about bark beetle aggregation behavior in the 15 years since the first pheromone was identified from /. paraconfusus. It has also indicated how little we yet know about many of the behavioral aspects of aggregation. Our ability to make highly resolved enantiomers of pheromones opens the way to analyse these behaviors more precisely. Similarly, the biosynthesis of pheromones from host compounds, the orientation mechanisms used by beetles in flight, the pheromone production of individual beetles, and their interaction with sonic and visual stimuli can now all be used to understand the many behavioral steps taken by individual beetles from eclosion to mating and egg laying, which will result in a composite picture of tree colonization built up from information rather than intuitive assumptions. 

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