Chondroitin sulfate alleviates leaf senescence of Chinese flowering cabbage by modulating homeostasis of ROS and chlorophyll catabolism during storage

Abstract

Chinese flowering cabbage is a nutrient abundance and popular vegetable while being sensitive to leaf senescence after harvest. Herein, the application of chondroitin sulfate (CS), a glycosaminoglycan, to delay the postharvest leaf senescence of Chinese flowering cabbage were comprehensively investigated. CS treatment could effectively inhibit the changes of yellowing index, chromaticity values of L* , C* , hue angle, and decrease of chlorophyll content in leaf of Chinese flowering cabbage. The expression levels of chlorophyll degradation catabolic genes BrNYC1, BrSGR1, BrSGR2, BrPPH, BrPAO, and BrRCCR, and representative senescence associated genes BrSAG12 and BrSAG21 were evidently repressed by CS as compared to control. The treatment of CS slowed down the production of the superoxide radical (O₂^-.), hydrogen peroxide (H₂O₂) and malondialdehyde. The activity enzyme of nicotinamide adenine dinucleotide phosphate oxidase (NOX), and the transcript abundance of respiratory burst oxidase homologues (RBOH) genes of BrRbohB, BrRbohC, BrRbohD, BrRbohD2 and BrRbohE were retarded. Additionally, the activity of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) was maintained, and their corresponding genes BrCAT3, BrCu/Zn-SOD1, BrPOD42, and BrAPX5 were up-regulated. These findings indicate that application of CS might potentially delay the leaf senescence by modulating ROS homeostasis and chlorophyll degradation for Chinese flowering cabbage during storage.