Poster: Metabolic engineering

Abs # 289: Production of γ -linolenic acid and stearidonic acid in marker-free transgenic soybean

Presenter:	Howe, Arlene R, ahowe2@unlnotes.unl.edu
Authors	Howe, Arlene R (A) (B)  Eckert, Helene  (A) (C)  Sato, Shirley  (A) (B)  LaVallee, Brad  (A) (B)  Schoneweis, Susan  (A) (C)  Graef, George  (A) (C)  Clemente, Tom  (A) (D)
Affiliations:	(A): University of Nebraska (B): Center for Biotechnology (C): Dept. of Argronomy & Horticulture (D): Plant Science Initiative

Polyunsaturated fatty acids (PUFAs) have attracted much interest because of their increasing number of nutraceutical and pharmaceutical applications. Two examples of PUFAs used in this way are γ-linolenic acid (GLA) and stearidonic acid (STA). GLA and STA are the delta-6 desaturation products of linoleic acid and α-linolenic acid, respectively. We recently introduced the Borago officinalis L.Δ6 desaturase gene, under the control of the seed-specific promoter β-conglycinin, into soybean via Agrobacterium-mediated transformation utilizing a two T-DNA binary system. This strategy permitted the recovery of marker-free transgenic soybean lines that harbored only the Δ6 desaturase cassette. A T₃ homozygous, marker-free transgenic line designated 420-5, grown under greenhouse conditions, was evaluated in the T₄ generation under field conditions. Average GLA levels of T₃ seeds in the greenhouse ranged from 29.8% to 34.1% and STA levels ranged from 3.7% to 5.1%. Under field conditions, at the T₄ generation, GLA levels averaged 23.7% to 30.4%, while average STA levels were observed at 2.1% to 2.9%. The Δ6 desaturase T-DNA element within line 420-5 appears to be a simple integration event with 1 to 2 copies based on Southern hybridization. Soybean sequence proximal to the right border element has been analyzed. We are currently exploring avenues to enhance the STA component of the seed storage lipids by dual expression of the B. officinalis L. δ6 desaturase combined with an Arabidopsis Ω-3 desaturase (FAD3) gene.