Production of γ-linolenic acid in Lotus japonicus and Vigna angularis by expression of the Δ6-fatty-acid desaturase gene isolated from Mortierella alpina

The Δ6-fatty-acid desaturase gene isolated from Mortierella alpina 1S-4 was introduced into Lotus japonicus and Vigna angularis by Agrobacterium-mediated transformation and constitutively expressed. Two transgenic L. japonicus lines accumulated γ-linolenic acid (GLA, C18:3, n-6), which was not found in the host, at levels of up to 11.34 and 9.66% of the total fatty acids in the leaves, respectively. These results indicate that the legume plant can synthesize GLA by expressing the fungus gene. The ability to synthesize GLA was also inherited by their progenies, which accumulated levels of up to 12.82 and 13.75% of the total fatty acids in the leaves, and 2.39 and 2.65% of those in the seeds. The GLA also accumulated at levels of up to 0.44 and 1.26% of the total fatty acids in the leaves and seeds, respectively, of a transgenic V. angularis line and at 0.69% in the leaves of its progeny. These findings reveal that the modification of the fatty-acid biosynthetic pathway by genetic manipulation in order to produce specific polyunsaturated fatty acids in grain legume crops is a promising technique.