Inhibition of polyunsaturated fatty acid accumulation in plants expressing a fatty acid epoxygenase

Earlier, we described the isolation of a Crepis palaestina cDNA (Cpal2) which encoded a Δ12-epoxygenase that could catalyse the synthesis of 12,13-epoxy-cis-9-octadecenoic acid (18:1E) from linoleic acid (18:2). When the Cpal2 gene was expressed under the control of a seed-specific promoter in Arabidopsis plants were able to accumulate small amounts 18:1E and 12,13-epoxy-cis-9,15-octadec-2-enoic acid in their seed lipids. In this report we give results obtained from a detailed analysis of transgenic Arabidopsis plants containing the Cpal2 gene. The seeds from these plants accumulate varying levels of 18:1E, but show a marked increase in 18:1 and equivalent decrease in 18:2 and 18:3. We further observed that the co-expression of a C. palaestina Δ12-desaturase in Arabidopsis appears to return the relative proportions of the C₁₈ seed fatty acids to normal levels and results in a 2-fold increase in total epoxy fatty acids.