Molecular modification of triacylglycerol accumulation by over-expression of DGAT1 to produce canola with increased seed oil content under field conditions

The final step in the Kennedy pathway for seed oil synthesis is catalyzed by an acyl-CoA-dependent diacylglycerol acyltransferase, DGAT1 (EC. 2.3.1.20). We have cloned DGAT1 genes from both Arabidopsis thaliana (L.) Heynh ecotype Columbia and Brassica napus 'Jet Neuf' and over-expressed them in canola under the control of the seed-specific promoter, napin. DGAT1 from A. thaliana was inserted into B. napus 'Quantum,' whereas DGAT1 from B. napus was introduced into the B. napus double haploid breeding line DH12075. Both sets of transgenic plants exhibited increased seed oil content in both greenhouse and in field trial settings, ranging from 2.5% to 7% of dried mass on an absolute basis. The 'Quantum' transgenic lines were field-tested in plots at Watrous, Saskatchewan, in 2006 and 2007. Larger scale field trials of the DH12075 transgenics were carried out in 2007 at Ellerslie and Vegreville, Alberta. This is the first study wholly dedicated to DGAT1 over-expression and the resultant oil-content increases in transgenic canola under field conditions. Collectively, the field trial results strongly support the hypothesis that the level of DGAT1 activity during seed development in an oilseed crop can have a substantial effect on the flow of carbon into seed oil. Therefore, the over-expression of DGAT1 is a positive strategy for increasing oil content and cultivar performance in canola.