Ips paraconfusus

P-A50 converts a-plnene to several oxidized products after Induction by a-plnene, and to at least one oxidized product without prior Induction (36). Rat liver cytochrome P-A50 also converts a-plnene to oxidation products (36) and this activity Is Induced by phenobarbltol and 3-naphthoflavone. There Is also the Interesting possibility that the bacterial flora In the bark beetles may contribute to the oxidation of a-plnene to trans- and cls-verbenol, A bacterium, Bacclllus cereus. Isolated from the hind-gut of Ips paraconfusus catalyses these oxidations (37). 

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. 

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. 

Figure 6.11 Biosyntheses of isoprenoid pheromone components by bark and ambrosia beetles from host conifer monoterpenes. (A) Conversion by the male California fivespined ips, Ips paraconfusus Lanier (Coleoptera Scolytidae), of myrcene from the xylem and phloem oleoresin of ponderosa pine, Pinus ponderosa Laws., to (4S)-(+)-ipsdienol and (4S)-(-)-ipsenol, components of the aggregation pheromone (Hendry et al., 1980). (B) Conversion by male and female I. paraconfusus of (1 S,5S)-(-)-a-pinene (2,6,6-trimethyl-bicyclo[3.1,1]hept-2-ene) from the xylem and phloem oleoresin of P. ponderosa to (1 S,2S,5S)-(+)-c/s-verbenol (c/s-4,6,6-trimethyl-bicyclo[3.1,1]hept-3-en-2-ol), an aggregation pheromone synergist and of (1 R,5R)-(+)-a-pinene to (1 fl,2S,5fl)-(+)-frans-verbenol (frans-4,6,6-trimethyl-bicyclo[3.1,1]hept-3-en-2-ol), a compound of unknown behavioral activity for /. paraconfusus. Male and female western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera Scolytidae), convert (1 S,5S)-(-)-a-pinene to (1S,2ft,5S)-(-)-frans-verbenol, an aggregation pheromone interruptant and (1R,5R)-(+)-a-pinene to (1 R,2S,5R)-(+)-frans-verbenol, a compound of...

Figure 6.13 Examples of the application of normal-phase, radio-HPLC to the analysis of de novo biosynthetic pathways in bark beetles (Scolytidae). Demonstration of sex-specific de novo biosynthesis of ipsenol, ipsdienol, and amitinol through radio-HPLC analysis of pentane extracts of Porapak-trapped volatiles from (A) male and (B) female Ips paraconfusus Lanier feeding for 168 h in Pinus ponderosa and (C) male and (D) female Ips pini (Say) feeding for 168 h in Pinus jeffreyi (Seybold et al., 1995b). Demonstration of sex-specific de novo biosynthesis of frontalin through radio-HPLC analysis of pentane extracts of Porapak-trapped volatiles from (E) male and (F) female...

Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, which had been previously treated with juvenile hormone III (JH III, 2.2 pg/beetle in acetone) and then placed in an aeration tube for 25 to 30 h. Ips paraconfusus and I. pini were each injected with 0.2 pCi of sodium [1-14C]acetate prior to placement in cut pine logs and volatile collection, while D. jeffreyi were each injected with 3.8 (male) and 3.7 (female) pCi of sodium [1-14C]acetate 6.4 (male) and 10.7 (female) h after JH application. (G) The role of the mevalonate pathway in frontalin biosynthesis is supported by the incorporation of radiolabel from [2-14C]mevalonolactone into frontalin by male D. jeffreyi (2.2 pg JH 11 l/beetle in acetone, 10 h incubation and volatile collection, 1.1 pCi of [2 14C] mevalonolactone injected, 20 h volatile collection). Figures adapted from Seybold et al. (1995b) and Barkawi (2002). 

Figure 6.15 Hypothetical alternative late stages of enantiospecific de novo biosynthesis of ipsenol and ipsdienol in male Ips paraconfusus and Ips pini. Biosynthesis may proceed from geranyl diphosphate to myrcene as catalyzed by a sex-specific monoterpene synthase. Terpene synthases (including a myrcene synthase) have been characterized from conifers (Bohlmann et al. 1997, 1998). Alternatively, biosynthesis may proceed from geranyl diphosphate to 5-hydroxygeranyl diphosphate (W. Francke, personal communication).

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.

Byers J. A. (1983b) Influence of sex, maturity and host substances on pheromones in the guts of the bark beetles, Ips paraconfusus and Dendroctonus brevicomis. J. Insect Physiol. 29, 5-13. 

Chen N. M., Borden J. H. and Pierce H. D., Jr (1988) Effect of juvenile hormone analog, fenoxycarb, on pheromone production by Ips paraconfusus (Coleoptera Scolytidae). J. Chem. Ecol. 14, 1087-1098. 

Fish R. H., Browne L. E., Wood D. L. and Hendry L. B. (1979) Pheromone biosynthetic pathways conversions of deuterium-labelled ipsdienol with sexual and enantioselectivity in Ips paraconfusus. Tetrahedron Lett. 17, 1465-1468. 

Fish R. H., Browne L. E. and Bergot B. J. (1984) Pheromone biosynthetic pathways conversion of ipsdienone to (-)-ipsdienol, a mechanism for enantioselective reduction in the male bark beetle, Ips paraconfusus. J. Chem. Ecol. 10, 1057-1064. 

Ivarsson P., Tittiger C., Blomquist C., Borgeson C. E., Seybold S. J., Blomquist G. J. and Hogberg H.-E. (1998) Pheromone precursor synthesis is localized in the metathorax of Ips paraconfusus Lanier (Coleoptera Scolytidae). Naturwissenschaften 85, 507-511. 

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. 

Addition of an allylsilane to acid chlorides has been used to synthesize ipsenol and ipsdienol, principal components of the aggregation pheromone of the bark beetle Ips paraconfusus (Figure Si6.3). It is of note that the allylsilane used in these syntheses is a versatile source of the isoprene unit. 

However, whereas the silkworm female appears to attract males with a single sex pheromone, many other insects use blends of pheromones as chemical releasers of behavior. This phenomenon is strikingly illustrated in the case of males of the bark beetle Ips paraconfusus (=Ips confusus) which utilize three monoterpene alcohols as an aggregation pheromone (11). Maximum attraction of beetles in the field was exhibited in the presence of a mixture of all three compounds, whereas single or pairs of compounds were considerably less active (12). Similarly, in laboratory bioassays, mixtures of compounds were vastly superior to single constituents as attractants (13). 

Scolytidae. The worldwide ranges of bark beetles have made them ideal candidates for research directed toward the isolation and identification of pheromones that can be used for population monitoring and regulation. A decade ago, the aggregative pheromone liberated by males of Ips paraconfusus (=confusus) was identified as a mixture of (-)-2-methyl-6-methylene-7-octen-4-ol (ipsenol) (XVI), (+)-cis-verbenol (XVII), and (+)-2-methyl-6-methylene-2,7-octadien-4-ol (ipsdienol) (XVIII)... 

The faecal pellets of the bark beetle Ips paraconfusus which had fed on the phloem of Pinus ponderosa contained large quantities of the aggregation pheromones cis-verbenol (24), ipsenol (25), and ipsdienol (26). The pheromones originate in the hindgut, but, although there is a precursor-product correlation between a-pinene or myrcene from the phloem and the pheromone terpenoids, the biosynthetic site is unclear. The demonstration68 of the conversion of a-pinene into cis- and trans-verbenol (27) by Bacillus cereus found in the gut of I. paraconfusus has led to the... 

Bark beetles are of great economic importance, which is one of the reasons more research has been done on the pheromones of the Scolytidae than on those of any other family of Coleoptera. Their pheromone systems also seem to be typical of the Coleoptera in that while there is considerable diversity in pheromone structure within this family, there also seems to be a pattern of structures, particularly within a genus. The first pheromone identified from a coleopterous species was from Ips paraconfusus Lanier (then I. confusus) by Silverstein et al. (13). Three compounds — ipsenol (I), ipsdienol (II), and cis-verbenol (III)... 

The first insect sex pheromone to be identified was bombykol, (E,Z)-10,12-hexadecadien-l-ol [58]. The elucidation of the structure spanned 20 years and required half a million female abdomens. A few years later, (Z)-7-dodecenyl acetate was identified as the sex pheromone of the cabbage looper, Trichoplusia ni [59]. Silverstein worked on bark beetles, in which three terpenes were identified as a synergistic pheromone blend for Ips paraconfusus [60], and it became reeognised that most insect pheromones consisted of multicomponent blends. 

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