The synthesis and accumulation of stearidonic acid in transgenic plants: a novel source of ?￠????heart?￠????healthy?￠???? omega?￠????3 fatty acids

摘要

Dietary omega?￠????3 polyunsaturated fatty acids have a proven role in reducing the risk of cardiovascular disease and precursor disease states such as metabolic syndrome. Although most studies have focussed on the predominant omega?￠????3 fatty acids found in fish oils (eicosapentaenoic acid and docosahexaenoic acid), recent evidence suggests similar health benefits from their common precursor, stearidonic acid. Stearidonic acid is a ????6?￠????unsaturated C18 omega?￠????3 fatty acid present in a few plant species (mainly the Boraginaceae and Primulaceae ) reflecting the general absence of ????6?￠????desaturation from higher plants. Using a ????6?￠????desaturase from Primula vialii , we generated transgenic Arabidopsis and linseed lines accumulating stearidonic acid in their seed lipids. Significantly, the P. vialii ????6?￠????desaturase specifically only utilises ???±?￠????linolenic acid as a substrate, resulting in the accumulation of stearidonic acid but not omega?￠????6 ???3?￠????linolenic acid. Detailed lipid analysis revealed the accumulation of stearidonic acid in neutral lipids such as triacylglycerol but an absence from the acyl?￠????CoA pool. In the case of linseed, the achieved levels of stearidonic acid (13.4% of triacylglycerols) are very similar to those found in the sole natural commercial plant source ( Echium spp.) or transgenic soybean oil. However, both those latter oils contain ???3?￠????linolenic acid, which is not normally present in fish oils and considered undesirable for heart?￠????healthy applications. By contrast, the stearidonic acid?￠????enriched linseed oil is essentially devoid of this fatty acid. Moreover, the overall omega?￠????3/omega?￠????6 ratio for this modified linseed oil is also significantly higher. Thus, this nutritionally enhanced linseed oil may have superior health?￠????beneficial properties.