Exogenous Nitric Oxide Mediated Redox Metabolism And Regulation Mechanism Of Chilling Injury In Jujube Fruit

Chilling injury is the most important abiotic stress damage in the process of cold storage and transportation of postharvest fruits.In severe cases,it will cause cell death and aggravate microbial infection,and then lose the commercial value.Nitric oxide(NO)is a key signaling molecule in plants,and plays an important role in the response of fruits to abiotic stress.In this paper,sodium nitroprusside(SNP)was used as exogenous NO donor to soak jujube fruits(Ziziphus jujuba Mill.).The effects of chilling stress and exogenous NO on the storage quality of jujube fruit were studied.Quantitative proteomic and S-nitrosylation proteomic were used to analyze the differentially expressed proteins and S-nitrosylation differentially modified proteins in jujube fruit,and to further verify the gene expressions of key enzymes in the redox metabolic pathway of jujube fruit.The results are as follows:The chilling injury index and weight loss index of jujube fruit increased during cold storage.Exogenous NO inhibited the increase of chilling injury rate and weight loss rate of jujube fruit,and improved the quality of jujube fruit.Exogenous NO inhibited the decrease of L*,firmness,total phenolics and flavonoids content of jujube fruit under chilling stress during storage,and improved the storage quality and antioxidant capacity of jujube fruit under chilling stress.At the same time,the increase of electrolyte leakage and malondialdehyde content of jujube fruit was reduced,and the oxidative damage of jujube fruit was delayed under chilling stress.A total of 5,836 proteins were identified by TMT labeled quantitative proteomics,among which 143 proteins were up-regulated and 181 proteins were down-regulated under chilling stress.And exogenous NO significantly up-regulated 42 proteins and down-regulated 46 proteins.These differentially expressed proteins mainly involved cellular and metabolic processes,and their subcellular structure was mainly located in the nucleus,chloroplast and cytoplasm.In addition,1,045 S-nitrosylated proteins and1,653 S-nitrosylated sites were identified by S-nitrosylation proteomic.The differentially modified proteins of S-nitrosylation caused by chilling stress and exogenous NO mainly included cellular processes,metabolic processes and stimulus responses,and their subcellular structural localization was mainly in chloroplasts and cytoplasm.The contents of AsA and GSH in jujube fruit increased at the early stage of storage under chilling stress,and jujube fruit used AsA and GSH to resist chilling stress.With the increase of storage time,the contents of AsA and GSH decreased,and exogenous NO inhibited the decrease of ASA and GSH.The result of RT-qPCR showed that exogenous NO increased the expression of ZjSOD,ZjCAT,ZjAPX,ZjDHAR,ZjGPX and ZjGSNOR genes in redox metabolism of jujube fruit.The results showed that exogenous NO alleviated the occurrence of chilling injury and improved the quality of jujube fruit during storage.Both chilling stress and exogenous NO had significant effects on the protein expression and S-nitrosylation of jujube fruit,and the differential proteins were mainly involved in cellular and metabolic processes.The redox metabolism related proteins modified by S-nitrosylation maintained the redox homeostasis of cells and improved the quality of jujube fruits under chilling stress.This research provided a deep insight into the effect of exogenous NO in fruit chilling injury,and shed light on the application of exogenous NO on postharvest preservation.