Exogenous sucrose treatment accelerates postharvest tomato fruit ripening through the influence on its metabolism and enhancing ethylene biosynthesis and signaling

The role of sucrose as a signal molecule in plants was in debate for a long time, until recently, it gradually becomes more prominently accepted. Sucrose plays roles in a vast array of developmental processes in plants, however, its function in fruit ripening has not been well elucidated. In this study, the influence of exogenous sucrose treatment (500 mM) on postharvest tomato fruit ripening was investigated. It was found that, in comparison with mannitol treatment (500 mM, set as control), sucrose accelerated the ripening process with higher levels of respiration rate and ethylene production during the storage. Sucrose treatment up-regulated its biosynthetic genes, whilst stimulated expressions of genes encoding degradation related enzymes in the fruits. However, higher sucrose content was observed in sucrose-treated fruits only in the first few days. In addition, sucrose application had minor effect on the contents of its degrading products, glucose and fructose. Moreover, exogenous sucrose treatment up-regulated expressions of ethylene biosynthetic genes, and promoted ethylene signal transduction via influencing critical genes of the signaling pathway in different patterns. These results indicate that sucrose stimulates tomato fruit ripening may through mediating its own metabolism, which facilitates nutrients fluxes and metabolic signaling molecules activation, and also by enhancing ethylene biosynthesis and signal transduction.