November 25, 2014

Seminar: Conifer terpenes: Engineering an Ancient Plant Defense Pathway for Renewable Chemicals and Biofuels

This week we were paid a visit by Prof. Gary F. Peter from the University of Florida. Despite a bizarre series of technical hangups, fire alarms, and presentation snafus, Prof. Peter demonstrated great composure and provided us with an excellent summary on the current state of knowledge regarding the metabolic engineering of Loblolly and Slash pine to increase the terpenoid content of trees as a source of biofuels. Unlike cellulosic based biofuels, the largely reduced nature of olefinic terpene hydrocarbons make them a superior source of fuel that does not have the same fermentation requirements of cellulosic starting material. Terpene resins, as Prof. Peter described them, are "cheap enough to burn". In this presentation, he describes a statistical approach to identifying traits linked to higher accumulations of terpene resins in pine using association genetics, functional genomics, and metabolic engineering.

I admit a personal bias on this research topic since I wrote my dissertation on terpene synthases of Loblolly pine. Nonetheless, Prof. Peter did an excellent job of illustrating the need to de-regulate outplanting of transgenic trees for biofuel production, a sustainable solution to providing reliable, carbon neutral energy sources from renewable materials. Interestingly, his research group has made excellent progress on engineering the "motor" of plastidial isoprenoid biosynthesis, the 2C-methylerythritol 4-phosphate (or MEP) pathway. In particular, in collaboration with Jay Keasling and Jack Kirby from the Joint Bioenergy Institute in Berkeley, California, his group has found that upregulation of rate controlling enzymes of the MEP pathway, such as 1-deoxyxylulose 5-phosphate synthase (DXS), is just as effective at increasing terpene accumulation as is the introduction of MEP pathway intermediates through alternative entry point using intermediates common to photosynthesis. One example is a modified form of the E. coli protein RibB, which converts ribulose 5-phosphate into 1-deoxyxylulose 5-phosphate, providing the first committed intermediate of the MEP (at least in plants) from common metabolic intermediates in the plastid without the loss of carbon associated with the DXS reaction, which is partially powered through the elimination of the stable leaving group CO2. This alternative entry point into the MEP pathway represents an improvement on the efficiency of this step and paves the way for future improvements of terpene production in pine. When combined with the considerable genetic resources and traditional breeding programs available in this species, pine is becoming a more and more attractive platform for sustainable, carbon neutral energy production. Everyone at our institute was happy to meet Gary and ask him questions following his presentation. Let's hope the public resistance to using genetically modified organisms to meet our environmental challenges can be overcome by better education so that we can take advantage of these exciting new technologies to make the world a better and cleaner place to live in. Thanks for an excellent presentation, Gary.

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