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 omega3/6 Delta(8)-desaturation biosynthetic pathways for the formation of C20 polyunsaturated fatty acids. Arabidopsis thaliana was transformed sequentially with genes encoding a Delta(9)-specific elongating activity from Isochrysis galbana, a Delta(8)-desaturase from Euglena gracilis and a Delta(5)-desaturase from Mortierella alpina. Instrumental in the successful reconstitution of these C20 polyunsaturated fatty acid biosynthetic pathways was the I. galbana C18-Delta(9)-elongating activity, which may bypass rate-limiting steps present in the conventional Delta(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.