Resin Detoxification in Dendroctonus ponderosae: Functional Characterizations of Cytochrome P450 Proteins

Abstract

A growing epidemic of pine tree deforestation in North America can largely be attributed to a particular pest, the Mountain Pine Beetle (MPB, Dendroctonus ponderosae). Coupling pheromone-coordinated mass attacks with an ability to resist the trees’ natural defenses allows the beetles to overwhelm their targets and burrow beneath the tree bark to reproduce. MPB use cytochrome P450 enzymes to both detoxify toxic monoterpene compounds present in tree resin as well as synthesize the pheromones used during tree invasion, suggesting an evolutionary link between the P450 proteins involved in the two processes. This study attempts to contribute to the understanding of this evolutionary link by examining CYP6DH3, a P450 closely related to a known MPB resin detoxifier CYP6DH2. To do so, microsomal CYP6DH3 was expressed in Sf9 insect cells before being separated and incubated with various monoterpene substrates. GC screening revealed that no products could consistently be formed, which suggested an issue with the assay protocol. Various adjustments to the procedure have allowed the results of a previous study (Song et al., 2013) to be replicated, though further testing must be done to confirm whether these reaction conditions apply to CYP6DH3.