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Title: CO-EXPRESSION OF THE BORAGE DELTA-6 DESATURASE AND THE ARABIDOPSIS DELTA-15 DESATURASE RESULTS IN HIGH ACCUMULATION OF STEARIDONIC ACID IN THE SEEDS OF TRANSGENIC SOYBEAN

Author
item ECKERT, HELENE - UNIVERSITY OF NEBRASKA
item LAVALLEE, BRAD - UNIVERSITY OF NEBRASKA
item SCHWEIGER, BRUCE - DUPONT
item KINNEY, ANTHONY - DUPONT
item CAHOON, EDGAR
item CLEMENTE, TOM - UNIVERSITY OF NEBRASKA

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2006
Publication Date: 5/23/2006
Citation: Eckert, H., Lavallee, B., Schweiger, B.J., Kinney, A.J., Cahoon, E.B., Clemente, T. 2006. Co-expression of the borage delta-6 desaturase and the Arabidopsis delta-15 desaturase results in high accumulation of stearidonic acid in the seeds of transgenic soybean. Planta (online) http://www.springerlink.com/content/u723701867067850/.

Interpretive Summary: Soybean oil is a rich source of omega-6 polyunsaturated fatty acids, which have limited nutritional value for food and animal feed. Metabolic engineering studies were conducted to enhance the composition of soybean oil. These studies resulted in the production of soybean seeds with oils enriched in the more nutritious omega-3 polyunsaturated fatty acids alpha-linolenic acid and steridonic acid. The soybean seeds generated in these studies will provide valuable research material for evaluation by nutritionists and animal scientists, especially those involved in the development of vegetable-based aquaculture feed. This research will ultimately increase the value of soybeans for US farmers and processors and will lead to more nutritious, heart-healthy vegetable oils for consumers.

Technical Abstract: Two relatively rare fatty acids, gamma-linolenic acid (GLA) and stearidonic acid (STA) have attracted much interest due to their nutraceutical and pharmaceutical potential. STA, in particular, has been considered a valuable alternative source for omega-3 fatty acids due to its enhanced conversion efficiency in animals to eicosapentaenoic acid when compared with the more widely consumer omega-3 fatty acid, alpha-linolenic acid, present in most vegetable oils. Exploiting the wealth of information currently available in planta oil biosynthesis and coupling this information with the tool of genetic engineering, it is now feasible to deliberately perturb fatty acid pools to generate unique oils in commodity crops. In an attempt to maximize the STA content of soybean oil, a borage delta-6 desaturase and an Arabidopsis delta-15 desaturase were pyramided by either sexual crossing of transgenic events, re-transformation of a delta-6 desaturase event with the delta-15 desaturase, or co-transformation of both desaturases. Soybean events that carried only the delta-15 desaturase displayed a significant elevation of alpha-linolenic acid content, while events with both desaturases displayed a relative STA abundance greater than 29 percent, creating a soybean with omega-3 fatty acids representing over 60 percent of the fatty acid profile. Analyses of the membrane lipds in a subset of the transgenic events suggest that soybean seeds compensate for enhanced production of polyunsaturated fatty acids by increasing the relative content of palmitic acid in phosphatidylcholine and other phospholipids.