EXPRESSION OF A BORAGE DESATURASE CDNA CONTAINING AN N-TERMINAL CYTOCHROME B(5) DOMAIN RESULTS IN THE ACCUMULATION OF HIGH-LEVELS OF DELTA(6)-DESATURATED FATTY-ACIDS IN TRANSGENIC TOBACCO

gamma-linolenic acid (GLA; C18:3 Delta(6,7,12)) is a component of the seed oils of evening primrose (Oenothera spp.), borage (Borago officin alis L.), and some other plants. It is widely used as a dietary supple ment and for treatment of various medical conditions. GLA is synthesiz ed by a Delta(6)-fatty acid desaturase using linoleic acid (C18:2 Delt a(9,12)) as a substrate. To enable the production of GLA in convention al oilseeds, we have isolated a cDNA encoding the Delta(6) fatty acid desaturase from developing seeds of borage and confirmed its function by expression in transgenic tobacco plants. Analysis of leaf lipids fr om a transformed plant demonstrated the accumulation of GLA and octade catetraenoic acid (C18:4 Delta(6,9,12,15)) to levels of 13.2% and 9.6% of the total fatty acids, respectively. The borage Delta(6)-fatty aci d desaturase differs from other desaturase enzymes, characterized from higher plants previously, by the presence of an N-terminal domain rel ated to cytochrome b(5).