Characterization of blueberry monodehydroascorbate reductase gene and changes in levels of ascorbic acid and the antioxidative capacity of water soluble antioxidants upon storage of fruits under various conditions

Blueberry (Vaccinium corymbosum) is among the richest fruits in ascorbic acid (AA), which is the most important antioxidant involved in the ascorbate–glutathione cycle. In this cycle monodehydroascorbate reductase (MDAR) is the enzymatic component involved in the regeneration of reduced ascorbate. Here we report on the isolation of a full-length cDNA from blueberry encoding a protein of 433 amino acids homologous to the MDARs of Pisum sativum and Vitis vinifera. To assess changes in the expression of blueberry MDAR after harvest, a storage trial was initiated, and the major results were: (1) A dramatic loss in AA occurred under all storage conditions. However, storing fruit under low O2, combined with high CO2 level (up to 18%) resulted in better preservation of AA. (2) The antioxidative capacity of water soluble antioxidants (ACW) decreased under all storage conditions, even after 3 weeks storage time, and decreasing O2 levels did not result in preservation of the ACW. The northern blot hybridization showed a clear differential expression between freshly harvested and stored fruits as well as between fruits stored under various storage condition, in accordance with the above-mentioned changes.In conclusion, this study clearly indicates that consumption of freshly harvested blueberries is highly recommended over the stored berries. Moreover, further work is needed to elucidate reasons for the quality loss over the storage period, in particular at the molecular level.