Vitamin C (ascorbic acid) is an essential component for collagen biosynthesis and also for the proper
functioning of the cardiovascular system in humans. Unlike most of the animals, humans lack the ability
to synthesize ascorbic acid on their own due to a mutation in the gene encoding the last enzyme of
ascorbate biosynthesis. As a result, vitamin C must be obtained from dietary sources like plants. In this
study, we have developed transgenic potato plants (Solanum tuberosum L. cv. Taedong Valley) overexpressing
strawberry GalUR gene under the control of CaMV 35S promoter with increased ascorbic acid
levels. Integration of the GalUR gene in the plant genome was confirmed by PCR and Southern blotting.
Ascorbic acid (AsA) levels in transgenic tubers were determined by high-performance liquid
chromatography (HPLC). The over-expression of GalUR resulted in 1.6–2-fold increase in AsA in
transgenic potato and the levels of AsA were positively correlated with increased GalUR activity. The
transgenic lines with enhanced vitamin C content showed enhanced tolerance to abiotic stresses
induced by methyl viologen (MV), NaCl or mannitol as compared to untransformed control plants. The
leaf disc senescence assay showed better tolerance in transgenic lines by retaining higher chlorophyll as
compared to the untransformed control plants. Present study demonstrated that the over-expression of
GalUR gene enhanced the level of AsA in potato tubers and these transgenics performed better under
different abiotic stresses as compared to untransformed control