Publications

• Functional characterization of myrcene hydroxylases from two geographically distinct Ips pini populations.

  Song M., Kim A.C., Gorzalski A.J., MacLean M., Young S., Ginzel M.D., Blomquist G.J., Tittiger C.

  Ips pini bark beetles use myrcene hydroxylases to produce the aggregation pheromone component, ipsdienol, from myrcene. The enantiomeric ratio of pheromonal ipsdienol is an important prezygotic mating isolation mechanism of I. pini and differs among geographically distinct populations. We explored ... >> More

  Ips pini bark beetles use myrcene hydroxylases to produce the aggregation pheromone component, ipsdienol, from myrcene. The enantiomeric ratio of pheromonal ipsdienol is an important prezygotic mating isolation mechanism of I. pini and differs among geographically distinct populations. We explored the substrate and product ranges of myrcene hydroxylases (CYP9T2 and CYP9T3) from reproductively-isolated western and eastern I. pini. The two cytochromes P450 share 94% amino acid identity. CYP9T2 mRNA levels were not induced in adults exposed to myrcene-saturated atmosphere. Functional assays of recombinant enzymes showed both hydroxylated myrcene, (+)- and (-)-α-pinene, 3-carene, and R-(+)-limonene, but not α-phellandrene, (-)-β-pinene, γ-terpinene, or terpinolene, with evidence that CYP9T2 strongly preferred myrcene over other substrates. They differed in the enantiomeric ratios of ipsdienol produced from myrcene, and in the products resulting from different α-pinene enantiomers. These data provide new information regarding bark beetle pheromone evolution and factors affecting cytochrome P450 structure-function relationships. << Less

  Insect Biochem Mol Biol 43:336-343(2013) [PubMed] [EuropePMC]

• Functional expression of a bark beetle cytochrome P450 that hydroxylates myrcene to ipsdienol.

  Sandstrom P., Welch W.H., Blomquist G.J., Tittiger C.

  The final steps in the pheromone-biosynthetic pathway of the pine engraver beetle, Ips pini (Say) (Coleoptera: Scolytidae) are unknown, but likely involve myrcene (7-methyl-3-methylene-1,6-octadiene) hydroxylation to produce the aggregation pheromone component, ipsdienol (2-methyl-6-methylene-2,7- ... >> More

  The final steps in the pheromone-biosynthetic pathway of the pine engraver beetle, Ips pini (Say) (Coleoptera: Scolytidae) are unknown, but likely involve myrcene (7-methyl-3-methylene-1,6-octadiene) hydroxylation to produce the aggregation pheromone component, ipsdienol (2-methyl-6-methylene-2,7-octadien-4-ol). We have isolated a full-length I. pini cDNA encoding a cytochrome P450, CYP9T2. The recovered cDNA is 1.83kb and the open reading frame encodes a 532 amino acid protein. CYP9T2 is regulated by the same physiological factors that induce pheromone production. Quantitative real-time PCR experiments showed that feeding on host phloem induced CYP9T2 expression in males, but not females, and that basal expression levels are highest in male midguts, similar to other I. pini pheromone-biosynthetic genes. Microsomes prepared from Sf9 cells co-expressing baculoviral-mediated recombinant CYP9T2 and housefly (Musca domestica) NADPH-cytochrome P450 reductase converted myrcene to ipsdienol. The product identified by coupled GC-MS was mostly (4R)-(-)-ipsdienol, an important aggregation pheromone component for western North American I. pini. These results are consistent with CYP9T2 encoding a myrcene hydroxylase that functions near the end of the pheromone-biosynthetic pathway. << Less

  Insect Biochem Mol Biol 36:835-845(2006) [PubMed] [EuropePMC]