Scientists have for the first time genetically modified plants to contain a particularly healthy kind of fatty acid in their seeds. The most beneficial of so-called omega-3 fatty acids are found only in fish, so growing omega-3-rich transgenic plants instead could increase public consumption while relieving pressure on fisheries, researchers say.
The oil and fat in food consist of fatty acids, which are chains of carbon and hydrogen atoms. The most healthy variety, polyunsaturated fatty acids, have two or more double bonds between the carbon atoms. Among these, omega-3 and omega-6 fatty acids--for example, docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)--confer the greatest benefit, lowering the risk of cardiovascular disease and other ills.
Fish are a good source of DHA and EPA. Plants don't contain either, but precursors of these fatty acids are fairly abundant in flaxseed, canola oil, soybeans, and walnuts. The human body can synthesize DHA from these precursors, although not efficiently. Because most people don't eat enough fish to get the recommended amount of EPA, and because fisheries are already in decline, researchers have been trying to engineer plants with enzymes to make EPA. In June, a group reported success with the model plant Arabidopsis; by adding three genes, researchers led by Baoxiu Qi of the University of Bath, U.K., created plants in which EPA made up 20% of the plant's oils.
Now, another group led by botanist Ernst Heinz of the University of Hamburg, Germany, has done the same in flax. This plant was a logical starting place, because its seeds have the highest levels of omega-3 precursors. Heinz, biochemist Amine Abbadi, and colleagues added a different trio of genes than Qi's team used. The genes introduced by the German group encode enzymes that add carbon double bonds to the precursors and tack on additional carbon atoms, creating a range of omega-3 and other fatty acids.
Omega-3 and omega-6 made up 3.6% of the fatty acids in the transgenic seeds, the team reports in the October issue of The Plant Cell. Although this is still less than a tenth of what's found in fish oil, Heinz says that a spoonful of transgenic linseed oil (made from crushed flaxseed) would provide most of what's recommended for good health. The team has also figured out which step in the reactions is limiting the amount of omega-3 and omega-6 and is working to improve the yield.
"It's a good step forward," Qi says, although she notes that the EPA in the seeds is scanty. Boosting that level probably won't be a major hurdle, notes Alan McHughen of the University of California, Riverside, who has worked on transgenic linseed. The bigger challenge, he and Heinz both say, will be winning public acceptance, especially in Europe. But because this transgenic crop would provide a health benefit for consumers, plus an environmental benefit, they and Qi are hopeful.