Pericarp browning occurs widely in postharvest pomegranate fruit, but little is known about its mechanism. In this study, ‘Baiyushizi’, a browning-sensitive cultivar, was used to investigate the physiological and genetic changes during pericarp browning. The pericarp browning index (BI) increased greatly after 3 d storage at room temperature, and, consequently, the fruit appearance became unattractive after 6 d. The increasing concentration of malondialdehyde (MDA) and electrolyte leakage were detected in browning pericarp. Polyphenol oxidase (PPO) activity increased significantly after 3 d, while ascorbate peroxidase (APX) and catalase (CAT) activity decreased steadily during storage. Total phenolics content decreased gradually during storage, while ascorbic acid (AsA) and glutathione (GSH) contents increased firstly, then declined. Differentially expressed genes (DEGs) of pericarp under different browning degrees were identified in the metabolic processes of phenolic compounds, lipids, ascorbic acid, glutathione, sugar, starch, energy-related, ethylene biosynthesis and signal transduction pathways. Accordingly, the potential metabolic pathways and related processes involved in pericarp browning were described. The results not only provided insights on the genetic mechanism of pericarp browning in pomegranate but also guidance on controlling postharvest fruit browning in general.

The pomegranate (Punica granatum L.) fruit is favorable for its nutrient-rich benefits to human health. However, the global metabolic profiles of pomegranate juice and the metabolic mechanisms of its essential metabolites are poorly understood. In this study, we conducted a widely targeted metabolome, integrated with the transcriptome of juices (edible parts) of pomegranate fruits at 50, 95, and 140 days after flowering (DAF) to comprehensively investigate the metabolic profiles and potential metabolism of essential metabolites. Five hundred and nine metabolites, including 11 sugar and sugar alcohols, 17 common organic acids, 20 essential amino acids, and a variety of flavonoids, were detected in pomegranate juices. Among them, metabolites in the flavonoid biosynthesis pathway greatly changed during fruit development. Notably, the redirection of metabolite flux from catechin and its derivative synthesis to anthocyanin synthesis occurred at the later developmental stages. The increased expression of Pgr021399.1 encoding dihydroflavonol 4-reductase (DFR), Pgr017842.1 encoding anthocyanidin synthesis (ANS), Pgr015322.1 encoding anthocyanidin 3-O-glucosyltransferase (BZ1), Pgr000447.1 encoding UTG75C1, and the decreased expression of Pgr024128.1 encoding leucoanthocyanidin reductase (LAR) may trigger redirection. The results of this study provide a global view of the metabolic profiles of pomegranate juices and valuable information on the molecular mechanisms underlying the redirection of flavonoid metabolism. It also sheds light on the genetic regulation of flavonoid metabolism in pomegranate juices.