Transcriptome and Metabolome Integrated Analysis Revealed the Effects and Potential Mechanism of Hydrogen Peroxide on Antioxidant System in Postharvest Broccoli

To investigate the effects and potential mechanism of exogenous H2O2 on antioxidant metabolism and yellowing in postharvest broccoli, the transcriptome and metabolome integrated analysis were performed. A total of 61 differentially expressed genes and 6 differentially accumulated metabolites identified among of H2O2 and diphenylene iodonium (DPI) treatments on 2 and 4 d. Exogenous H2O2 promoted the accumulation of endogenous H2O2 within 1 d by activating RBOHs expressions·H2O2 treatment up-regulated the expressions of SOD, CAT and peroxiredoxin (Prx) genes and APX, DHAR and GPX genes involved in ascorbic acid-glutathione (AsA-GSH) cycle, thereby promoting the scavenging of O2-. and H2O2 and alleviating the oxidative damage. Additionally, H2O2 treatment promoted the biosynthesis of AsA and GSH, and increased the content of AsA, GSH, oxidized glutathione, and γ-glutamylcysteine·H2O2 treatment also promoted glucosinolate biosynthesis, the accumulation of 3-(6′-methylthio)hexylmalic acid, and the production of sulforaphane by up-regulating MYS expression, thereby enhancing the health-care function of postharvest broccoli. This study provided the new insights into regulatory mechanism of H2O2 on antioxidant system.