A transcriptomic and metabolomic approach to the physiological adaptation of ‘Bayushizi’ pomegranate fruit to sunburn browning

Sunburn browning is a major physiological disease of the ‘Bayushizi’ pomegranate fruit that significantly affects its appearance and internal quality. At present, the underlying mechanisms of sunburn browning in ‘Baiyushizi’ pomegranates remain unclear. This study aims to elucidate the physiological adaptations, metabolic shifts and potential genetic regulation underlying sunburn browning in ‘Baiyushizi’ pomegranates. Sunburn browning induces pericarp cell shrinkage and lignification, leading to increases in H2O2, O2− and MDA levels, indicating that sunburn browning causes membrane lipid peroxidation. This further leads to enzymatic reactions (increased SOD and CAT contents) and nonenzymatic reactions (increased total flavonoid, carotenoid and total phenolic contents) in the pericarp of the pomegranate. Metabolomic analysis revealed that flavonoids, phenolic acids, coumarins and lignans characterized the sunburn browning of pomegranates. The physiological characteristics were integrated with transcriptomic data for weighted correlation network analysis (WGCNA). Regulatory networks were used to identify key genes and transcription factors (TFs) that influence flavonoid, phenolic acid, coumarin and lignan metabolism during sunburn browning. These findings provide insight into the physiological adaptation, metabolic shifts and potential genetic regulation of the effects of pomegranates on sunburn browning.