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  • Open Access

Metabolic engineering of hydroxy fatty acid production in plants: RcDGAT2 drives dramatic increases in ricinoleate levels in seed oil

Authors

  • Julie Burgal,

    1. Institute of Biological Chemistry, Clark Hall, Washington State University, Pullman, WA 99164-6340, USA
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    • These authors contributed equally to this work.

  • Jay Shockey,

    1. Institute of Biological Chemistry, Clark Hall, Washington State University, Pullman, WA 99164-6340, USA
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    • These authors contributed equally to this work.

    • Present address: Southern Regional Research Center, United States Department of Agriculture-Agricultural Research Service, 1100 Robert E. Lee Blvd., New Orleans, LA 70124, USA

  • Chaofu Lu,

    1. Institute of Biological Chemistry, Clark Hall, Washington State University, Pullman, WA 99164-6340, USA
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    • §

      Present address: Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA

  • John Dyer,

    1. USDA-ARS, US Arid-Land Agricultural Research Center, 21881 North Cardon Lane, Maricopa, AZ 85238, USA
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  • Tony Larson,

    1. Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5YW, UK
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  • Ian Graham,

    1. Centre for Novel Agricultural Products, Department of Biology, University of York, York YO10 5YW, UK
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  • John Browse

    Corresponding author
    1. Institute of Biological Chemistry, Clark Hall, Washington State University, Pullman, WA 99164-6340, USA
      * Correspondence (fax 509-335-7643; e-mail jab@wsu.edu)
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* Correspondence (fax 509-335-7643; e-mail jab@wsu.edu)

Summary

A central goal of green chemistry is to produce industrially useful fatty acids in oilseed crops. Although genes encoding suitable fatty acid-modifying enzymes are available from many wild species, progress has been limited because the expression of these genes in transgenic plants produces low yields of the desired products. For example, Ricinus communis fatty acid hydroxylase 12 (FAH12) produces a maximum of only 17% hydroxy fatty acids (HFAs) when expressed in Arabidopsis. cDNA clones encoding R. communis enzymes for additional steps in the seed oil biosynthetic pathway were identified. Expression of these cDNAs in FAH12 transgenic plants revealed that the R. communis type-2 acyl-coenzyme A:diacylglycerol acyltransferase (RcDGAT2) could increase HFAs from 17% to nearly 30%. Detailed comparisons of seed neutral lipids from the single- and double-transgenic lines indicated that RcDGAT2 substantially modified the triacylglycerol (TAG) pool, with significant increases in most of the major TAG species observed in native castor bean oil. These data suggest that RcDGAT2 prefers acyl-coenzyme A and diacylglycerol substrates containing HFAs, and biochemical analyses of RcDGAT2 expressed in yeast cells confirmed a strong preference for HFA-containing diacylglycerol substrates. Our results demonstrate that pathway engineering approaches can be used successfully to increase the yields of industrial feedstocks in plants, and that members of the DGAT2 gene family probably play a key role in this process.

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