ENZYMATIC PROCESSES FOR INCREASING INDUSTRIAL UTILIZATION OF VEGETABLE OILS
Location: Commodity Utilization Research
Title: Type 1 and Type 2 Diacylglycerol Acyltransferases from Developing Seeds of Tung (Vernicia Fordii) Display Different Affinities for Eleostearic Acid-Containing Substrates.
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2005
Publication Date: June 10, 2005
Citation: Shockey, J.M., Gidda, S., Chapital, D.C., Kuan, J.-C.W., Rothstein, S.J., Mullen, R.T., and Dyer, J.M. 2005. Type 1 and type 2 diacylglycerol acyltransferases from developing seeds of tung (Vernicia fordii) display different affinities for eleostearic acid-containing substrates (abstract). 2005 Biochemistry and Molecular Biology of Plant Fatty Acids and Glycerolipids Symposium, Abstract C3, page 11, June 10-14, Fallen Leaf Lake, CA. 2005:22
Tung is one of many oilseed plants that accumulate high levels of unusual fatty acids in the triacylglycerol fraction of seed lipids. Unlike the phospholipids, which contain the typical 16- and 18-carbon fatty acids common to most plants, tung triacylglycerols contain approximately 80% eleostearic acid (18:3 delta9cis,11trans,13trans). The oxidative properties of eleostearic acid make tung oil one of the best drying oils known to man. However, like many other exotic oilseeds, tung has poor agronomic traits that hinder widespread cultivation in North America. Our group seeks to engineer tung-like oils in transgenic plants and microbes by reconstitution of the complete tung oil biosynthetic pathway. Toward this end, we have focused on diacylglycerol acyltransferase (DGAT), an enzyme that catalyzes the committed step in triacylglycerol biosynthesis, and is widely considered to be a potential regulatory point for control of both the quantitative and qualitative flux through this pathway. Interpretation of the importance of DGAT is complicated by the fact that at least two types of DGAT enzymes exist in most plant species. Full-length cDNAs for type 1 and type 2 DGATs and the single-copy genes that encode them have been isolated from tung and characterized. Northern blot analyses revealed that the two genes were differentially regulated in a temporal manner; DGAT1 is expressed at relatively constant levels throughout seed development, while DGAT2 is strongly upregulated coincident with the onset of oil deposition. DGAT2 also displays a 5-fold greater ability to synthesize trieleostearin in a yeast functionality assay, compared to DGAT1. These results suggest that the two DGAT enzymes fulfill distinctly different roles in developing tung seed, and indicate that tung DGAT2 may be more useful in future microbial and oilseed engineering programs.