Studies On Regulation And Molecular Mechanism Of Gibberellin Treatment On Ripening Of Postharvest Kiwifruit

Fruit ripening and maturation is a genetically programmed event that is complicated through complex metabolic processes,such as pigment accumulation,softening,aroma and flavor characteristics.As a typical climacteric fruit,kiwifruit ripening and softening are important factors affecting the storage period after harvest.In this study,the effects of gibberellin and chitosan on the storage quality of postharvest kiwifruit were studied.At the same time,the key genes of fruit ripening and softening were screened by using bioinformatics analysis and gene expression techniques.Which provides some reference value for the storage and preservation of postharvest kiwifruit.Gibberellins（GAs）is among the most classical phytohormones that control numerous processes in plants,including fruit ripening.However,the role of GAs in kiwifruit ripening is unclear.In this study,GA₃ was applied to the postharvest storage’Gold No.1’,’Longcheng No.2’and’Hongyang’kiwifruit.The date showed that GA₃treatment significantly delayed the decrease in firmness and the increase in soluble solid content（TSS）,inhibited the production of ethylene,and delayed the ripening process of kiwifruit after harvest,and the 0.3 g/L GA₃treatment is the best choice.In addition,many physiological traits in’Hongyang’kiwifruit were further detected,such as starch content,ascorbic acid（vitamin C）concentration,cell-wall components（pectin,cellulose and hemicellulose）,and ester production.The results showed that GA₃ delayed the degradation of fruit starch and cell wall,as well as the production of esters.Moreover,the transcriptome analysis supplied a molecular basis for investigating the inhibiting mechanism of GA₃ and metabolic variations during kiwifruit ripening.A total of 3116differently expressed genes（DEGs）were identified,including 51 genes involved in plant hormone signal transduction pathway and 36 structural genes related to these physiological traits.Then,16 major DEGs were analyzed by real-time PCR during the whole storage period.The expression of most of them was significantly suppressed by GA₃ treatment,such as two ethylene biosynthesis genes（ACOs）,twoβ-amylase（BAMs）,five cell-wall modification genes,one GA2ox,and one GA receptor GID1,whereas the expression of Actinidia29942（JAZ）was enhanced by GA₃ treatment.In addition,a total of 8 key transcription factors（TFs）were identified by transcription factor analysis,and the results of real-time PCR analysis showed that the expression of Actinidia09616（Ac NAC4）and Actinidia39788（Ac NAC083）was significantly inhibited by GA₃ treatment.Furthermore,the correlation analysis between multiple physiological indicators and key candidate genes showed that GA₃ could regulate kiwifruit postharvest ripening effectively and comprehensively.Together,these GA-responsive genes may play important roles in controlling kiwifruit ripening,and GA₃ treatment could be a promising approach for the preservation of postharvest kiwifruit.