Redirection of metabolic flux for high levels of omega-7 monounsaturated fatty acid accumulation in camelina seeds.

Seed oils enriched in omega-7 monounsaturated fatty acids, including palmitoleic acid (16:1∆9) and cis-vaccenic acid (18:1∆11), 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 ∆9 desaturation of stearoyl (18:0)-acyl carrier protein (ACP) to ∆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 ∆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 fatty acid accumulation to 60-65% 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 ∆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 nontransformed 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.

[1]  V. Shulaev,et al.  Imaging heterogeneity of membrane and storage lipids in transgenic Camelina sativa seeds with altered fatty acid profiles. , 2013, The Plant journal : for cell and molecular biology.

[2]  K. Mockaitis,et al.  Camelina seed transcriptome: a tool for meal and oil improvement and translational research. , 2013, Plant biotechnology journal.

[3]  J. Browse,et al.  Reducing saturated fatty acids in Arabidopsis seeds by expression of a Caenorhabditis elegans 16:0-specific desaturase. , 2013, Plant biotechnology journal.

[4]  M. Ramos,et al.  Biodiesel from Camelina sativa: A comprehensive characterisation , 2013 .

[5]  E. Cahoon,et al.  Genetic and biochemical basis for alternative routes of tocotrienol biosynthesis for enhanced vitamin E antioxidant production. , 2013, The Plant journal : for cell and molecular biology.

[6]  A. Hatanaka,et al.  Chronic administration of palmitoleic acid reduces insulin resistance and hepatic lipid accumulation in KK-Ay Mice with genetic type 2 diabetes , 2011, Lipids in Health and Disease.

[7]  D. Mozaffarian,et al.  Trans-Palmitoleic Acid, Metabolic Risk Factors, and New-Onset Diabetes in U.S. Adults , 2010, Annals of Internal Medicine.

[8]  T. A. Walsh,et al.  Metabolic Engineering of Seeds Can Achieve Levels of ω-7 Fatty Acids Comparable with the Highest Levels Found in Natural Plant Sources1[OA] , 2010, Plant Physiology.

[9]  M. Meier.  Metathesis with Oleochemicals: New Approaches for the Utilization of Plant Oils as Renewable Resources in Polymer Science , 2009 .

[10]  G. Knothe,et al.  A Comprehensive Evaluation of the Melting Points of Fatty Acids and Esters Determined by Differential Scanning Calorimetry , 2009 .

[11]  A. Ribeiro,et al.  Instrumental Methods for the Evaluation of Interesterified Fats , 2009 .

[12]  M. Meier,et al.  Metathesis as a versatile tool in oleochemistry , 2008 .

[13]  Christoph Benning,et al.  Plant triacylglycerols as feedstocks for the production of biofuels. , 2008, The Plant journal : for cell and molecular biology.

[14]  Chaofu Lu,et al.  Generation of transgenic plants of a potential oilseed crop Camelina sativa by Agrobacterium-mediated transformation , 2008, Plant Cell Reports.

[15]  J. Shanklin,et al.  Modulating seed β-ketoacyl-acyl carrier protein synthase II level converts the composition of a temperate seed oil to that of a palm-like tropical oil , 2007, Proceedings of the National Academy of Sciences.

[16]  A. Kinney,et al.  Conjugated fatty acids accumulate to high levels in phospholipids of metabolically engineered soybean and Arabidopsis seeds. , 2006, Phytochemistry.

[17]  Jürgen Krahl,et al.  The Biodiesel Handbook , 2005 .

[18]  Y. Man,et al.  Recent developments in differential scanning calorimetry for assessing oxidative deterioration of vegetable oils , 2002 .

[19]  Baoru Yang,et al.  Triacylglycerols, glycerophospholipids, tocopherols, and tocotrienols in berries and seeds of two subspecies (ssp. sinensis and mongolica) of Sea Buckthorn (Hippophaë rhamnoides). , 2002, Journal of agricultural and food chemistry.

[20]  E. Cahoon,et al.  Substrate-dependent mutant complementation to select fatty acid desaturase variants for metabolic engineering of plant seed oils. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[21]  J. Watts,et al.  A palmitoyl-CoA-specific Δ9 fatty acid desaturase from Caenorhabditis elegans. , 2000 .

[22]  R. Abbott,et al.  Serum lipid effects of a high-monounsaturated fat diet based on macadamia nuts. , 2000, Archives of internal medicine.

[23]  C. P. Tan,et al.  Differential scanning calorimetric analysis of edible oils: Comparison of thermal properties and chemical composition , 2000 .

[24]  K. Feldmann,et al.  Arabidopsis FAD2 gene encodes the enzyme that is essential for polyunsaturated lipid synthesis. , 1994, The Plant cell.

[25]  A. Shibahara,et al.  Determination of double-bond positions in methylene-interrupted dienoic fatty acids by GC-MS as their dimethyl disulfide adducts , 1991 .

[26]  D. Yermanos,et al.  The Oil and Protein in Nuts of Macadamia tetraphylla L. Johnson, Macadamia integrifolia Maiden and Betche, and Their F1 Hybrid1 , 1973, Journal of the American Society for Horticultural Science.

[27]  W. J. Dyer,et al.  A rapid method of total lipid extraction and purification. , 1959, Canadian journal of biochemistry and physiology.

[28]  T. Clemente,et al.  The use of glufosinate as a selective agent in Agrobacterium-mediated transformation of soybean , 2004, Plant Cell, Tissue and Organ Culture.

[29]  W. Butte.  Rapid method for the determination of fatty acid profiles from fats and oils using trimethylsulphonium hydroxide for transesterification , 1983 .

[30]  M. Chisholm,et al.  Fatty acids of doxantha seed oil , 1965 .

[31]  T. Hilditch,et al.  492. The seed fat of Macadamia ternifolia , 1950 .