Effect of nitric oxide on sugar metabolism in peach fruit (cv. Xiahui 6) during cold storage

The influence of exogenous nitric oxide (NO) on the sucrose metabolism of peach fruit (cv. Xiahui 6) under cold storage was investigated. Peach fruit were treated with 10 mu L L-1 of NO at 25 +/- 1 degrees C for 3 h and then placed at 4 degrees C for twenty four days. The results showed that the ethylene production of the fruit treated with NO was inhibited significantly and the fruit had a higher firmness. Meanwhile, NO treatment could increase the activity of sucrose phosphate synthase (SPS) by enhancing the expression level of PpaSPS1/2. Similarly, as a sucrosecleaving enzyme gene, PpaAI1 encoding level reduced significantly compared to control fruit, resulting in lower sucrose-cleaving enzyme activity. Thus, NO also maintained higher sucrose content, but decreased glucose and fructose to lower levels during the late storage. We proposed that NO treatment may delay the senescence of fruit and sustain a higher sucrose content of peach fruit during cold condition.