Change of energy level and gene expression of NADP-dependent malic enzyme in apple fruit during refrigerated storage

In order to investigate the change of energy level and gene expression of NADP-dependent malic enzyme during storage, ‘Changfu 2'apple fruits were taken as experimental material. Fruit firmness, total soluble solid ( TSS) , the activity of NADP-dependent malic enzyme ( NADP-ME) and SDH, contents of ATP, ADP, AMP and energy charge were determined during storage.The results showed that the ATP content in apple fruit during storage period declined for the first 60 days thereafter recovering to storage beginning level, while the ADP and AMP content in fruit declined slightly for the first 60 days thereafter increased significantly. Both activities of NADP-ME and SDH declined gradually during whole storage period. The content of NADP+and NADPH in apple fruit performed similar trend with the energy charge that all increased obviously for the first 120 days then declined in the last 60 days.Although there was some difference on the time course, the gene expression of Mdcy ME1-Mdcy ME3 performed similar trend that they all increased during the early storage and then declined. These results demonstrated the energy levels and efficiency in apple fruits changed during storage and energy level has relevance with the activities and gene expression of NADP-ME.