Table 1: Approaches to increase ascorbic acid content through increasing ascorbate biosynthesis.

SpeciesEnzymeTissueGene sourceFold increase in AscComments Reference

TobaccoL-Galactose dehydrogenaseLeavesArabidopsisNo changeAntisense suppression resulted in lower Asc [37]
TobaccoGDP-L-galactose phosphorylaseLeavesKiwifruit3Transient overexpression by agroinfection [29]
ArabidopsisGDP-L-galactose phosphorylaseLeavesKiwifruit4Stable transformant [29]
TobaccoGDP- L-galactose phosphorylase and GDP-mannose-3′,5′-epimeraseLeaves Kiwifruit7Transient overexpression by agroinfection [29]
ArabidopsisD-Galacturonic acid reductaseLeavesStrawberry2 to 3Enzyme is from the D-galacturonate pathway [35]
TobaccoL-Gulono-1,4-lactone oxidase LeavesRat7No clear evidence that the animal Asc biosynthetic pathway exists in plants [38]
LettuceL-gulono-1,4-lactone oxidaseLeavesRat4 to 7No clear evidence that the animal Asc biosynthetic pathway exists in plants [38]
Arabidopsismyo-inositol oxygenaseLeavesArabidopsis2 to 3myo-inositol/D-glucuronate pathway [39]