Redirection of Metabolic Flux for High Levels of Omega-7 Monounsaturated Fatty Acid Accumulation... Print
Written by nguyen   
Monday, 05 May 2014 16:23
Plant Biotechnology Journal.
First published: 26 July 2014

Authors: Huu Tam Nguyen1, Hyunwoo Park2, Karen L. Koster3, Rebecca E. Cahoon1, Hanh TM Nguyen2, John Shanklin4, Thomas E. Clemente2, and Edgar B. Cahoon*1

Abstract

Seed oils enriched in omega-7 monounsaturated fatty acids, including palmitoleic acid (16:1D9) and cis-vaccenic acid (18:1D11), have nutraceutical and industrial value for polyethylene production and biofuels. Existing oilseed crops accumulate only small amounts (<2%) of these novel fatty acids in their seed oils. We demonstrate a strategy for enhanced production of omega-7 monounsaturated fatty acids in camelina (Camelina sativa) and soybean (Glycine max) that is dependent on redirection of metabolic flux from the typical delta 9 desaturation of stearoyl (18:0)-acyl carrier protein (ACP) to delta 9 desaturation of palmitoyl (16:0)-acyl carrier protein (ACP) and –coenzyme A (CoA). This was achieved by seed-specific co-expression of a mutant delta 9-acyl-ACP and an acyl-CoA desaturase with high specificity for 16:0-ACP and -CoA substrates, respectively. This strategy was most effective in camelina where seed oils with ~17% omega-7 monounsaturated fatty acids were obtained. Further increases in omega-7 monounsaturated fatty acid accumulation to ~ 65% of the total fatty acids in camelina seeds were achieved by inclusion of seed-specific suppression of 3-keto-acyl-ACP synthase II and the FatB 16:0-ACP thioesterase genes to increase substrate pool sizes of 16:0-ACP for the delta 9-acyl-ACP desaturase and by blocking C18 fatty acid elongation. Seeds from these lines also had total saturated fatty acids reduced to ~5% of the seed oil versus ~12% in seeds of non-transformed plants. Consistent with accumulation of triacylglycerol species with shorter fatty acid chain-lengths and increased monounsaturation, seed oils from engineered lines had marked shifts in thermotropic properties that may be of value for biofuel applications.

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1Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, 1901 Vine Street, Lincoln, NE 68588 USA

2Center for Plant Science Innovation and Department of Agronomy & Horticulture, University of Nebraska-Lincoln, 1901 Vine Street, Lincoln, NE 68588 USA

3Department of Biology, The University of South Dakota, 414 East Clark Street, Vermillion, SD 57069 USA

4Biosciences Department, Brookhaven National Laboratory, Upton, NY 11973 USA


T-DNAs used for generating high omega-7 unsaturated fatty acids in camelina seeds. 

Last Updated on Wednesday, 06 August 2014 22:16