Analysis of Flesh Browning, Expression Characteristics of Aquaporin Genes in ‘Yali’ Pear during Chilling Injury Induced by 1-MCP and MAP
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Abstract:
Fruit quality, flesh browning, expression characteristics of aquaporin genes in ‘Yali’ pear were analyzed during long-term cold storage. The ‘Yali’ fruit was treated with 1.0 μL/L of 1-methylcyclopropene (1-MCP), packaged with polyethylene film as modified atmosphere packaging (MAP), then was stored at 0 ℃ for 180 d and 20 ℃ for 7 d. During storage, fruit firmness, soluble solid contents (SSC) was analyzed, and gas (O2, CO2, ethylene) contents were measured; flesh browning rates, chlorogenic acid contents, polyphenol oxidase (PPO) and peroxidase (POD) activities in the flesh were measured. Expression characteristics of PbPIPs and PbTIPs were analyzed by Real-time PCR. The results showed that fruit firmness reduced and SSC increased during cold storage. The ethylene production in MAP was effectively restrained by 1-MCP treatment, and the peak ethylene content of 1-MCP+MAP-treated fruit was 17.30 μL/L. Fruit firmness was maintained by 1-MAP treatment and MAP respectively, whereas flesh browning was more serious. During long-term cold storage, the flesh browning rates and chlorogenic acid contents were higher in 1-MCP and MAP fruits, especially in 1-MCP+MAP treated fruit, the flesh browning rate was 25.78%. In addition, PPO and POD activities were high as well. During cold storage, the expression levels of PbPIP1;1 and PbTIP2;1 were down-regulated, while the expression levels of PbPIP1;4, PbPIP2;1, PbPIP2;2, PbPIP2;5 and PbTIP1;1 were up-regulated. The expressions of PbPIPs and PbTIPs tested were regulated by 1-MCP and 1-MCP+MAP. In conclusion, 1-MCP and MAP treatment could maintain fruit firmness and SSC in ‘Yali’ pear during long term storage, but caused serious flesh browning, which might be a consequence of high concentration CO2 and chilling injury. PbPIP2;1 and PbPIP2;5 participated the process of chilling injury, and could be regulated by low temperature and ethylene.
