Molecular Modification Of Triacylglycerol Accumulation By Over-Expression Of Dgat1 To Produce Canola With Increased Seed Oil Content Under Field Conditions1

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Molecular modification of triacylglycerol accumulation by over-expression of DGAT1 to produce canola with increased seed oil content under field conditions1
David C. Taylor, Yan Zhang, Arvind Kumar, Tammy Francis, E. Michael Giblin, ´ Dennis L. Barton, James R. Ferrie, Andre Laroche, Saleh Shah, Weiming Zhu, Crystal L. Snyder, Linda Hall, Gerhard Rakow, John L. Harwood, and Randall J.Weselake

Abstract: 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 seedspecific promoter, napin. DGAT1 from A. thalianawas 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, in2006 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 seeddevelopment in an oilseed crop can have a substantial effect on the flow of carbon into seed oil. Therefore, the overexpression of DGAT1 is a positive strategy for increasing oil content and cultivar performance in canola. Key words: cultivar improvement, Acyl-CoA:diacylglycerol acyltransferase 1, DGAT1, Arabidopsis, Brassica napus, double haploid (DH), seed oil content, field trials. ´ ´ ´ ` ´ ´ ´Resume : L’acyltranferase du diacylglycerol acyl-CoA-dependant, DGATI (EC.2.3.1.20) catalyse la derniere etape du sen` ´ ´ ` tier de Kennedy pour la synthese des huiles seminales. Les auteurs ont clone les genes DGATI de l’Arabidopsis thaliana ´ ´ ˆ (L.) Heynh. ecotype Columbia et du Brassica napus ‘Jet Neuf,’ et les ont surexprimes dans le canola sous le controle du ´ ´ ´ promoteur napin,specifique aux semences. Ils ont insere le DGATI de l’A. thaliana dans le B. napus ‘Quantum,’ et ont in¨ troduit le DGATI du B. napus dans la ligne de croisement double haploıde du B. napus DH12075. Les deux ensembles de ´ ´ plantes transgeniques ont montre une teneur accrue en huile dans les essais en serres aussi bien qu’aux champs, allant de ` ´ ´ ´ 2,5 a 7 % en poids sec sur une base absolue. Ils ontessaye en parcelles aux champs, les lignees transgeniques du ` ´ ` ´ ‘Quantum,’ a Watrous en Saskatchewan, en 2006 et 2007. Ils ont conduit des experiences a plus grande echelle avec les ´ ` ` ´ ` plantes transgeniques DH12075 en 2007 a Ellerslie et Vegreville en Alberta. Il s’agit de la premiere etude completement ´ ´ ` ´ ´ dediee a la surexpression du DGATI et des augmentations de la teneur enhuile qui en resulte chez le canola lors d’expe` ` ´ riences aux champs. Dans leur ensemble, les essais de terrain supportent fortement l’hypothese a l’effet que le degre d’ac´ ´ ´ tivite du DGATI au cours du developpement de la graine chez une oleagineuse peut avoir des effets substantiels sur le ´ ´ ´ flux de carbone vers les huiles seminales. Consequemment, la surexpression du DGATI constitueune strategie positive Received 12 May 2008. Published on the NRC Research Press Web site at botany.nrc.ca on 9 June 2009. This work is dedicated to the memory of our friend and colleague, Dr. Philip Raney. D.C. Taylor,2 Y. Zhang, A. Kumar, T. Francis, E.M. Giblin, and D.L. Barton. Plant Biotechnology Institute, National Research Council, Saskatoon, SK S7N 0W9, Canada. J.R. Ferrie. Viterra...