XVI International Botanical Congess

One of the most powerful antioxidants is ascorbic acid (Vitamin C, AsA). Recently progress has been made towards understanding plant AsA biosynthesis. Several AsA-deficient Arabidopsis mutants have been isolated. These mutants (vtc, vitamin c) represent four loci. The vtc mutants have varied sensitivities to oxidative stress. Two mutant alleles cause an altered AsA developmental phenotype. The vtc mutants are being used to identify genes involved in AsA biosynthesis. Evidence that the gene VTC1 encodes GDP-mannose pyrophosphorylase, an enzyme in a recently proposed AsA biosynthetic pathway will be presented. Three additional VTC genes are currently being cloned. We have biochemical evidence that suggests two of these VTC genes also encode proteins involved in AsA biosynthesis.