Regulatory Mechanisms By Nitric Oxide On Energy Metabolism And Cbf Depended Chilling Resistance In Postharvest Feicoeng Peach Fruit

The peach is one of the most popular fruit to the consumer,but peach fruits are difficult to store after harvest.Cold storage is a traditional and widely used method to retain freshness of peach fruits.However,the peach is chilling sensitive fruit.Cold storage usually leads to chilling injury and reduces the economic benefits of peach fruits.As an active small gas molecule,nitric oxide(NO)can alleviate the chilling injury and enhance the chilling resistance of postharvest peach fruits,but its regulation mechanism is unclear.Therefore,ascertaining the regulation mechanism by NO is of great significance to provide the theoretical basis for the fresh-keeping application of NO to peach fruits.The processes of ripening,senescence and physiological disorder of various types of postharvest fruit are associated with energy status.To explore the energy regulation mechanism by NO to ‘Feicheng' peach fruits during cold storage,‘Feicheng' peach fruits were picked at physiological mature,and treated with deionized water(as the control);5,15,30 ?mol L-1 NO and 5 ?mol L-1 c-PTIO solution.After treatment,the fruits were stored at 0 °C.The chilling injury index,firmness,the activities of H+-ATPase,Ca2+-ATPase,succinate dehydrogenase(SDH),cytochrome oxidase(CCO),and the contents of malondialdehyde(MDA),hydrogen peroxide,adenosine triphosphate(ATP),adenosine diphosphate(ADP),adenosine monophosphate(AMP)and the changes in energy charge in ‘Feicheng' peach fruits were measured at 0 d,1,2,3,4,5 weeks during storage.The results showed that,the contents of ATP,ADP,energy charge and the activities of SDH,CCO,H+-ATPase,Ca2+-ATPase decreased and the contents of AMP,H2O2 and MDA increased in peach fruits during storage.Compared to the control,NO treatment significantly restrained the decrease of ATP content,energy charge and the enzyme activities of SDH,CCO,H+-ATPase,Ca2+-ATPase and the increase of the contents of AMP,H2O2 and MDA in peach fruits during cold storage.Treatment with 15?mol L-1 NO showed the best effect.However,treatment with c-PTIO intensify the decrease of ATP content,energy charge and the enzyme activities of SDH,CCO,H+-ATPase,Ca2+-ATPase and the increase of the contents of AMP,MDA and H2O2 in peach fruits during cold storage.These results suggested that NO could effectively maintain the energy metabolism of peach fruits during storage.However,c-PTIO inhibited the energy metabolism of peach fruit.Plants can receive cold stimulation signal and adjust their own anti-cold system to resist cold.The cold signal is transmitted through the pathway: membrane protein receptor ? the second messenger(Ca2+)? protein kinase ? transcription factors ? cold resistance gene.The CBF gene is the core of botanic CBF anti-cold pathway.In this research,CBF family genes of “Feicheng” fruit were cloned through the correlation sequences in GDR.The CBF genes were sequenced,and finally the sequences of CBF1~6 were got.The fluorescence quantitative analysis results of CBF genes showed that the gene expression quantity of CBF1/5/6 in peach fruits rose rapidly and were maintained at a high level during cold storage.Compared with the control,treatment with NO significantly improved the expression level of CBF1/5/6.However,treatment wtih c-PTIO inhibited the expression of CBF1/5/6.The results proved the regulatory effect by NO on CBF depended cold resistance pathway.According to the CBF sequences,pET30a-CBF expression vectors were constructed,and the CBF1~3 proteins were expressed in vitro.The results laid the foundation for the further study about the anti-cold mechanism of NO.