Accumulation of γ-linolenic acid and stearidonic acid in rapeseeds that heterologously express the Phytophthora citrophthora Δ6 desaturase gene

Most oilseeds contain polyunsaturated fatty acids, such as linoleic acid (LA) and α-linolenic acid (ALA) that are important essential fatty acids for human health. γ-Linolenic acid (GLA) and stearidonic acid (SDA), synthesized from LA and ALA by Δ6 desaturase, respectively, are mainly obtained from algae and fish. Given the benefits of GLA and SDA to human health, many researchers have investigated ways to produce these fatty acids in oilseed crops. Canola-type oilseed rape (Brassica napus), widely cultivated in temperate and microthermal zones, accumulates oleic acid to a relatively greater extent (60–70% oleic acid content) than do other oilseed crops. We transformed the Phytophthora citrophthora Δ6 desaturase (PcD6DES) gene under the control of seed-specific vicilin into canola-type oilseed rape ‘Youngsan’. D6DES products (GLA, SDA, and 18:2Δ6,9) accumulated in mature PcD6DES-transformed rapeseeds and leaves. D6DES products of PcD6DES rapeseeds were over 20% in T1 and more than 25% in T2. Expression levels of the PcD6DES gene and the content of D6DES products coincided with each other and were related to expression levels and fatty acid composition in leaves and developing seeds 15, 25, 35, and 45 days after flowering. Seed weights of PcD6DES rapeseeds were not lower than those of Youngsan. In this study, PcD6DES oilseed rapes accumulated GLA, SDA, and putative 18:2Δ6,9 content to a maximum of 25% in the seed oil. Results show that PcD6DES rapeseed oil can potentially be used as a health food to improve human health.