Multi-omics analysis reveals the mechanism of calcium-reduced quality deterioration in mechanically injured green pepper fruit

Green pepper is regarded as one of the globally essential commercial crops with bright color and rich nutrition. However, green pepper is susceptible to mechanical injuries as a result of vibration, compression and impact events during postharvest handling and transportation. These injuries can induce physiological and biochemical abnormalities in fruit, thus accelerating fruit senescence and leading to economic losses. Calcium chloride (CaCl2) treatment is a safe, effective and economical method to maintain fruit quality during postharvest storage. Here, the impact of calcium treatment on the fruit quality of mechanically injured green pepper was investigated. The results indicated that calcium treatment maintained the sensory quality and hardness of green pepper fruit, inhibited redness development and elevation in the level of malondialdehyde (MDA). The combination of transcriptomics, metabolomics and assay for transposase accessible chromatin with high-throughput sequencing (ATAC-seq) revealed treatment effects of the expression of key genes related to fruit color change, fruit softening, active oxygen metabolism and hormone response, as well as changes of metabolites concentrations, and chromatin accessibility changes. A construction of regulatory network model of calcium treatment on post-harvest mechanical injury of green pepper fruit was developed based on these effects. Overall, the study provides valuable insights into the impact of mechanical injury on fruit after harvest and its amelioration by calcium.