Characterization of Ipsdienol Dehydrogenase in an Eastern Population of Ips pini.
AdvisorBlomquist, Gary J
Biochemistry and Molecular Biology
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Bark beetles are a major group of pest insects in North America. Each year, they destroy millions of acres of trees in the United States resulting in a huge economic loss. The objective of this study is to understand pheromone production in Ips spp.; specifically, how the stereochemistry of ipsdienol is achieved in an eastern population of Ips pini, which will be referred to as eastern I. pini The pheromone of eastern I. pini consists of an approximately 35:65 (R)-(-):(S)-(+). We hypothesized that the ipsdienol dehydrogenase in eastern I. pini, which will be referred to as eastern IDOL-DH, catalyzes the final step that determines ipsdienol stereochemistry. Eastern IDOL-DH was cloned and expressed in a baculovirus system. The enzyme was assayed by measuring the change in absorption at 340 nm, and its products analyzed by GC-MS on a chiral column to determine its role in achieving the final (R)-(-)/(S)-(+) ratio of ipsdienol. The results showed that recombinant eastern IDOL-DH interconverts (R)-(-) ipsdienol and ipsdienone and only produces the (R)-(-) ipsdienol from ipsdienone. The data suggest the final step to the natural occurring ratio of ipsdienol enantiomers was not carried out by eastern IDOL-DH. However, eastern IDOL-DH may play a role in the production of anti-aggregation pheromone, ipsenol, as it readily converted ipsenone to (S)-(-) ipsenol.