Characterization of oil exhibiting high γ‐linolenic acid from a genetically transformed canola strain

Abstract

The seed oil from a genetically transformed canola (Brassica napus) containing 43% (w/w) of γ-linolenic acid (G, 18:3n-6), 22% linoleic acid (L, 18:2n-6), and 16% oleic acid (O, 18:1n-9) was evaluated. In this high γ-linolenic acid canola oil (HGCO), the predominant 18:3n-6-containing triacylglycerol (TG) molecular species were GGL (23%), GLO (20%), and GGG (11%). In the total TG, approximately 75% of the 18:3n-6 was located at the sn-1,3 positions, while only 34% of linoleic acid was at the sn-1,3 positions. The GGL molecular species of HGCO contained approximately equal amounts of GLG and GGL positional isomers, while the GLO molecular species had 95% GOL and 5% GLO isomers. The general characteristics and the tocopherol and phytosterol contents were mostly similar between HGCO and nontransformed canola oil. No detectable amounts of amino acids and nucleotides were observed in the HGCO.Dietary supplementation of γ-linolenic acid (G, or ∆6,9,12-18:3, or 18:3n-6) is beneficial in many physiological and pathological conditions such as inflammatory diseases, cancer, and diabetes (1-4). Gamma (γ)-linolenic acid is commercially available mainly from the seed oils of borage, black currant, and evening primrose. It is also found in some fungi and algae such as Mortierella spp. and Spirulina spp. However, γ-linolenic acid-containing oils are not widely used due to their high production cost, fluctuation in availability, or safety concerns. In order to develop an economical, reliable, and wholesome source of γ-linolenic acid, we have genetically transformed a low α-linolenic acid canola plant into strains that can produce high levels of γ-linolenic acid (5). The nontransformed canola plants produce seed oils with large amounts of oleic (O, 18:1n-9) and linoleic (L, ∆9,12-18:2) acids. By introducing the ∆6-desaturase (converts L to G) and the ∆12-desaturase (converts O to L) genes from the fungus M. alpina, within a seed-specific expression vector, into canola plant cells, a high level of 18:3n-6 was produced in seeds of the genetically transformed canola plant. The seeds from the fifth generation field trial were crushed, and the oil was extracted and refined in a commercial facility. The oil is the first kind of genetically transformed canola oil that contains a high level of 18:3n-6. In this study, we evaluated the fatty acid composition, triacylglycerol (TG) molecular species, positional distribution of n-6 fatty acids, unsaponifiable matter (phytosterols and tocopherols), general quality, and nonlipid constituents of this high-18:3n-6 canola oil (HGCO) and compared them with properties of the oils from borage, black currant, evening primrose, and the nontransformed canola. EXPERIMENTAL PROCEDURESCanola oils. In this study, the seed oils from transgenic and nontransformed canola (Brassica napus) were analyzed. The method of cloning ∆12-and ∆6-desaturases from M. alpina and recombinant production of 18:3n-6 in plants was previously reported (5). Briefly, two cDNA clones with homology to known desaturase genes were is...

Soybean Oil: Genetic Approaches for Modification of Functionality and Total Content

“…Liu et al (2001) stacked a D12 and a D6 desaturase gene from the fungus Mortierella alpina in canola. This led to the accumulation of GLA to over 40% and SDA of approximately 2% in seeds.…”

Comparison of growth, serum biochemistries and n−6 fatty acid metabolism in rats fed diets supplemented with high-gamma-linolenic acid safflower oil or borage oil for 90days

“…The chemical and physical characteristics of this novel oil have been evaluated (Liu et al, 2001) as well as a series of animal studies conducted showing the bioequivalence and safety of HGCO to borage oil which is normally consumed by humans (Tso et al, 2002; Palombo et al, 2000; Liu et al, 2004; Wainwright et al, 2003). Recently, Arcadia Biosciences, Inc. (Davis, CA) has taken the steps to further development toward increasing GLA concentration and lowered costs in plant seed oils by producing a high GLA safflower oil (HGSO) comprising >40% GLA with a significantly reduced level of linoleic acid.…”

Co-expression of the borage Δ6 desaturase and the Arabidopsis Δ15 desaturase results in high accumulation of stearidonic acid in the seeds of transgenic soybean

“…In canola (Brassica napus) introduction of the fungal (Mortierella alpina) 6 and 12 desaturase genes led to the production of GLA and STA at 43 and 5%, respectively (Liu et al 2001). In brown mustard (B. juncea), expression of a 6 desaturase from the fungus Pythium irregulare resulted in GLA and STA levels up to 40 and 10%, respectively (Hong et al 2002).…”