Effects Of1-MCP On Ripening And Softening Of Papaya Fruit And Cloning, Expression Analysis Of Key Genes

Softening of postharvest fruit is one of the key factors which affect fruit storage life and quality in transportation. Delaying softening applicated by exogenous substances is the main trend for preservation. It is observed that1-MCP has good effects on many fruits and vegetables. The papaya fruit is one of the most widely cultivars in Hainan Province. But it belongs to climacteric fruit, so it is easily to turn yellow and softening, and cause postharvest losses. Effects of1-MCP on ripening and storage quality of'Risheng'papaya fruit was studied, and the key genes related to softening were also cloned and the expression level was investigated, the main results were shown as follows:1. Compared with the control fruit,1-MCP inhibited the degradation of chlorophyll, dalayed color changes of papaya peel, retarded the ethylene peak significantly, and suppressed fruit ripening; inhibited the activity of PG and Cx and PME, delayed fruit softening. However, ethephon accelerated the chlorophyll degradation and color change, promoted fruit softening; advanced ethylene peak, thus speeded up the maturity and softening process of the fruit. The relation analysis between fruit softening and enzyme activity changes shown that PG and Cx played an important role in ripening and softening of papaya.2. PG and Cx gene fragments were cloned from'Risheng' papaya flesh. The amino acid sequence of Cx gene fragment were highly similar with those of populus trichocarpa and fragariax ananassa. The result of blast suggested that Cx-cp has96%and95%sequence similarity with both Populus trichocarpa and Fragaria x ananassa. The amino acid sequence of PG gene fragment were highly similar with populus trichocarpa, vitis vinifera, oryza sativa Japonica Group. PG-cp has85%,84%,81%sequence similarity with Vitis vinifera, Oryza Sativa Japonica Group and Populus trichocarpa.3. The results shown that:the Cx gene expression increased firstly and then decreased with semi-quantitative PCR analysis on PG and Cx of papaya pulp with different treatment and in different storage time, Cx gene of papaya fruits treated with ethephon started a large number of expression in the first0.5days, and then decreased. Compared with control, the expression of Cx gene in fruits treated with1-MCP advanced0.5days and9days. A large number of expression in fruit treated with1-MCP was observed in the13th days, Cx gene expression of the control fruits expressed less at this time. For PG gene, large expression was presented in fruits treated with ethephon in the first day, however, there was almost no expression of PG genes in control fruits and the fruits treated with1-MCP during the all storage period.