Jeffreyi pheromone biosynthesis

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. 

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. 

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