Improving erucic acid content in rapeseed through biotechnology : What can the Arabidopsis FAE1 and the yeast SLC1-1 genes contribute ?

The main goal of our research is to produce, by genetic manipulation, Brassica napus L. cultivars with higher amounts of 22:1 in their seed oil than in present Canadian high erucic acid rapeseed (HEAR) cultivars developed through traditional breeding, ideally with proportions of 22:1 approaching 80 mol% (828 g [kg.sup.-1]). To probe some rate-limiting steps in the accumulation of triacylglycerols containing very long chain fatty acids (VLCFAs), particularly erucic acid (22:1), we have taken a transgenic approach, studying the effect of expressing two target genes in HEAR B. napus cv. Hero. To study the role of the elongase complex, involved in elongation of [C.sub.18] fatty acid moieties to produce VLCFAs, we expressed the Arabidopsis thaliana L., fatty acid elongase 1 (FAE1) gene under the control of a seed-specific promoter (napin), in Hero. This resulted in increased proportions of 22:1 in the seed oil, rising from 430 g [kg.sup.-1] in non-transformed controls to 480 to 530 g [kg.sup.-1] 22:1 in FAE1 transgenic Hero lines. The FAE1 lines exhibited higher elongase activity in vitro compared to control lines. These data suggest that the level of active condensing enzyme in the native elongase complex is somewhat rate limiting for synthesis of erucic acid and other VLCFAs in HEAR. In small scale field trials, the VLCFA and 22:1 content of FAE1 transgenic lines were superior to field-grown control lines. We report that in field plot trials, the progeny of our best [T.sub.4] B. napus cv. Hero SLC1-1 transgenic lines clearly out-performed controls in terms of 22:1, oil content, and yield.