Sanding the Rough Edges: In Search of Enhanced Performance of Engineered Enzymes in Transgenic Systems

Nature contains dozens of exotic seed oils containing high levels of unusual fatty acids that contain useful functionalities, such as epoxy and hydroxyl groups, or acetylenic and conjugated double bonds.  Produced at sufficient purity, these oils can be used as feedstocks in the production of variety of bio-based products.  Many of the basic biotechnological tools for engineering temperate oilseed crops are available, and many modest successes have been achieved. However, marketable success will require discovery of new genes and better understanding of their respective roles in lipid metabolism, as well as improvements in the techniques that we use to drive transgenic gene expression.  Diverged fatty acid desaturases (FADs) and diacylglycerol acyltransferases (DGATs) catalyze the first and last steps in the complex process of novel fatty acid synthesis and packaging, respectively.  In recent years, the tung tree (Vernicia fordii) FADX and DGAT2 genes have been studied with regard to its ability to enhance accumulation of alpha-eleostearic acid, a novel conjugated trienoic fatty acid. The expression of FADX in transgenic Arabidopsis has been optimized, and mutational analysis of tung DGAT2 revealed forms of the enzyme that outperform the native enzyme.  These findings, and a discussion of the additional challenges and bottlenecks that we now face, will be presented.