Production of γ‐Linolenic Acid and Stearidonic Acid in Seeds of Marker‐Free Transgenic Soybean 1

Through a single desaturation step, the Borago officinalis L. Δ 6 desaturase can convert linoleic acid and α‐linolenic acid to γ‐linolenic acid (GLA) and stearidonic acid (STA), respectively. Both GLA and STA are of interest to the pharmaceutical and nutraceutical industries. Production of these fatty acids is costly. One potential strategy to reduce production cost would be to generate them in a major oilseed crop. To this end, a cDNA of the B. officinalis Δ 6 ‐desaturase gene was cloned downstream of the embryo‐specific promoter β‐conglycinin. The resultant cassette was assembled into a two T‐DNA binary vector, in which the second T‐DNA element harbored a selectable marker cassette. The final plasmid was subsequently used to transform soybean [ Glycine max (L.) Merr.]. The simultaneous delivery of two T‐DNA elements was used as a strategy to derive soybean progeny transgenic for the Δ 6 desaturase T‐DNA and free of the marker gene T‐DNA. Twenty‐nine transgenic soybean lines were recovered that harbored both T‐DNA elements, of which 17 produced GLA and STA in the seed storage lipids. Average GLA levels ranged from 3.4 up to 28.7%, while STA levels varied from just under 0.6 to 4.2% in the T 1 generation. Among the 17 lines that produced GLA and STA, four lines were identified that were free of the selectable marker T‐DNA element.