Engineering increased vitamin C levels in plants by overexpression of a D-galacturonic acid reductase

Nat Biotechnol. 2003 Feb;21(2):177-81. doi: 10.1038/nbt777. Epub 2003 Jan 13.


L-Ascorbic acid (vitamin C) in fruits and vegetables is an essential component of human nutrition. Surprisingly, only limited information is available about the pathway(s) leading to its biosynthesis in plants. Here, we report the isolation and characterization of GalUR, a gene from strawberry that encodes an NADPH-dependent D-galacturonate reductase. We provide evidence that the biosynthesis of L-ascorbic acid in strawberry fruit occurs through D-galacturonic acid, a principal component of cell wall pectins. Expression of GalUR correlated with changing ascorbic acid content in strawberry fruit during ripening and with variations in ascorbic acid content in fruit of different species of the genus Fragaria. Reduced pectin solubilization in cell walls of transgenic strawberry fruit with decreased expression of an endogenous pectate lyase gene resulted in lower ascorbic acid content. Overexpression of GalUR in Arabidopsis thaliana enhanced vitamin C content two- to threefold, demonstrating the feasibility of engineering increased vitamin C levels in plants using this gene.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alcohol Oxidoreductases / biosynthesis*
  • Alcohol Oxidoreductases / genetics
  • Arabidopsis / genetics*
  • Arabidopsis / metabolism*
  • Ascorbic Acid / biosynthesis*
  • Ascorbic Acid / genetics
  • Cloning, Molecular
  • Energy Metabolism
  • Feasibility Studies
  • Fragaria / genetics
  • Fragaria / metabolism
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Plant
  • Hexuronic Acids / metabolism
  • Multienzyme Complexes / genetics
  • Multienzyme Complexes / metabolism
  • NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases
  • NADP / metabolism
  • Plants, Genetically Modified / enzymology
  • Plants, Genetically Modified / metabolism*
  • Protein Engineering / methods*
  • Species Specificity


  • Hexuronic Acids
  • Multienzyme Complexes
  • galacturonic acid
  • NADP
  • Alcohol Oxidoreductases
  • NAD (+) and NADP (+) Dependent Alcohol Oxidoreductases
  • D-galacturonate reductase
  • Ascorbic Acid