Transcriptomic and metabolomic analysis of the delay in chilling injury in green bell peppers (Capsicum annuum L.) by sodium hexametaphosphate

Green bell pepper fruits are prone to chilling injury (CI) during storage at low temperatures resulting in a loss in quality during transportation and marketing. We investigated the effect of a sodium hexametaphosphate (SHMP) treatment on CI in green bell peppers stored at 4 °C for 8 d followed by 3 d of shelf life using biochemical, transcriptomic, and metabolomic analyses. Results indicated that the SHMP treatment reduced both the CI rate and CI index, and extended product quality. A total of 2179 differentially expressed genes (DEGs) and 789 differentially abundant metabolites (DAMs) were found to be enriched in peppers treated with SHMP compared to the untreated, control group after 6 d of storage. The combined -omic and biochemical data revealed that SHMP altered lipid metabolism, resulting in the modification of glycerophospholipids and glycerolipids and reduced lipid oxidation. SHMP additionally enhanced phenylpropanoid metabolism, leading to the accrual of phenolic compounds such as gallic and p- hydroxybenzoic acid, as well as an elevation in arginine and proline. Additionally, antioxidant enzyme activity was enhanced, thereby mitigating the excessive accumulation of ROS. In summary, our collective results highlight the potential of SHMP to augment chilling tolerance in peppers.