Production of very long chain polyunsaturated omega-3 and omega-6 fatty acids in plants

We report the production of two very long chain polyunsaturated fatty acids, arachidonic acid (AA) and eicosapentaenoic acid (EPA), in substantial quantities in a higher plant. This was achieved using genes encoding enzymes participating in the ω3/6 Δ 8 -desaturation biosynthetic pathways for the formation of C20 polyunsaturated fatty acids. Arabidopsis thaliana was transformed sequentially with genes encoding a Δ 9 -specific elongating activity from Isochrysis galbana , a Δ 8 -desaturase from Euglena gracilis and a Δ 5 -desaturase from Mortierella alpina . Instrumental in the successful reconstitution of these C20 polyunsaturated fatty acid biosynthetic pathways was the I. galbana C18-Δ 9 -elongating activity, which may bypass rate-limiting steps present in the conventional Δ 6 -desaturase/elongase pathways. The accumulation of EPA and AA in transgenic plants is a breakthrough in the search for alternative sustainable sources of fish oils.