AbstractAlthough the primary biochemical pathway for L-ascorbic acid (AsA) biosynthesis was elucidated some years ago, there is still little information regarding either the molecular mechanisms controlling pathway flux or the factors controlling AsA accumulation in specific tissues. In order to increase understanding of these processes, we undertook a physiological, biochemical and molecular study of AsA accumulation in fruit of blackcurrant varieties representing low, medium and high fruit AsA phenotypes.
AsA accumulated early in fruit development in all three varieties and then remained constant. There was little evidence of significant transport of AsA from source tissues or storage reserves. The degree of AsA accumulation in each variety correlated with differences in fruit biosynthetic capacity. In all varieties, cessation of AsA accumulation correlated with a marked decrease in biosynthesis and increased rates of turnover. Current efforts are focussed on the analysis of biosynthetic gene expression in ripening blackcurrant fruit.