Investigation of the preharvest arginine spraying mechanism on antioxidant system in postharvest broccoli via transcriptomics and metabolomics

Abstract

According to our previous study, preharvest spraying of arginine for 1 day enhanced the antioxidant capacity of postharvest broccoli, but the underlying molecular mechanisms remain unclear. We here performed a comprehensive transcriptome and metabolome analysis to investigate the effects of arginine sprayed 1 day before harvest on the antioxidant capacity and yellowing of broccoli as well as the related action mechanisms. In total, 67 differentially expressed genes and 12 key differentially accumulated metabolites were identified in broccoli at 4 and 8 days during storage. Herein, the gene expression of superoxide dismutase, catalase, and the corresponding peroxisome protein Mpv17 (MPV17) was upregulated, consequently enhancing the scavenging of reactive oxygen species. Genes encoding glucosinolate synthesis- and metabolism-related enzymes were upregulated, and among them, the gene ST5b_c was upregulated by 8.23-fold, which promoted the accumulation of its metabolites. Expression of lignin- and flavonoid biosynthesis-related genes (CAD, POD, CHI, and CHS) was elevated. Flavonoid and lignin accumulation was promoted, with a greater antioxidant capacity at 4 and 8 days, respectively, in the arginine-sprayed broccoli. Additionally, the ascorbate–glutathione cycle was promoted in broccoli at 4 days, GLCAK and APX genes were upregulated by more than 2-fold, and broccoli exhibited a higher tolerance level because of the notably stimulated ascorbic acid and glutathione accumulation. This study offers new insights into the mechanisms through which preharvest spraying of arginine regulates the antioxidant capacity of postharvest broccoli.