Dendroctonus jeffreyi

Evidence for de novo synthesis of pheromone components was obtained by showing that labeled acetate and mevalonate were incorporated into ipsdienol by male Ips pini [103,104]. Similarly, labeled acetate and other labeled intermediates were shown to be incorporated into frontalin in a number of Dendroctonus species [105]. Possible precursors to frontalin include 6-methyl-6-hep-ten-2-one, which was incorporated into frontalin by D. ruffipennis [106]. The precursor 6-methyl-6-hepten-2-one also was shown to be converted to bre-vicomin in the bark beetle, Dendroctonus ponderosae [107]. In addition, the expression patterns of HMG-CoA reductase and HMG-CoA synthase are tightly correlated with frontalin production in Dendroctonus jeffreyi [108, 109]. A geranyl diphosphate synthase cDNA from I. pini was also isolated, functionally expressed, and modeled [110]. These data indicate that the de novo isoprenoid biosynthetic pathway is present in bark beetles. A variety of other monoterpene alcohols such as myrcenol, pityol, and sulcitol are probably synthesized through similar pathways [111]... 

Hall G. M., Tittiger C., Blomquist G. J., Andrews G., Mastick G., Barkawi L. A., Bengoa C. S. and Seybold S. J. (2002b) Male Jeffrey Pine Beetles, Dendroctonus jeffreyi, synthesize the pheromone component frontalin in anterior midgut tissue. Insect Biochem. Mol. Biol. 32, 1525-1532. 

Nardi J. B., Gilg Young A., Ujhelyi E., Tittiger C., Lehane M. J. and Blomquist G. J. (2002) Specialization of midgut cells for synthesis of male isoprenoid pheromone in two scolytid beetles, Dendroctonus jeffreyi and Ips pini. Tissue and Cell. 226, 221— 231. 

Specialization of midgut cells for synthesis of male isoprenoid pheromone components in two scolytid beetles, Dendroctonus jeffreyi and Ips pini. Tissue Cell. (in press). 

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). 

Barkawi L. S. (2002) Biochemical and molecular studies of aggregation pheromones of bark beetles in the genus Dendroctonus (Coleoptera Scolytidae), with special reference to the Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins. PhD thesis. Univ. Nevada, Reno, 193 pp. 

Paine T. D., Millar J. G., Hanlon C. C. and Hwang J.-S. (1999) Identification of semiochemicals associated with Jeffrey pine beetle, Dendroctonus jeffreyi. J. Chem. Ecol. 25, 433 153. 

Renwick J. A. A. and Pitman G. B. (1979) An attractant isolated from female Jeffrey pine beetles, Dendroctonus jeffreyi. Environ. Entomol. 8, 40-41. 

Figure 7.4 Regulation of HMG-R and HMG-S expression in male Dendroctonus jeffreyi by JH III. The time course (A, B) and dose response (C) for each gene in mature (emerged) males was investigated by northern blotting. All values are relative to starved, untreated males. Each point represents the mean +/- standard error of three replicates, five isolated thoraces/sample. Reproduced from Tittiger et al. (2000, 2003) with permission.

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. 

TITTIGER, C., BARKAWI, L.S., BENGOA, C.S., BLOMQUIST, G.J., SEYBOLD, S.J., Structure and juvenile hormone-mediated regulation of the HMG-CoA reductase gene from the Jeffrey pine beetle, Dendroctonus jeffreyi, Molec. Cell Endocrinol, 2003,199, 11-21. 

SIX, D.L., PAINE, T.D., Allozyme diversity and gene flow in Ophiostoma clavigerum (Ophiostomatales Ophiostomataceae), the mycangial fungus of the Jeffrey pine beetle, Dendroctonus jeffreyi (Coleoptera Scolytidae), Can. J. For. Res., 1999, 29, 324-331. 

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