Phenylpropanoid metabolism in relation to peel browning development of cold-stored 'Nanguo' pears. (September 2022) - Sun, Yangyang
Abstract: Cold-stored 'Nanguo' pears are susceptible to peel browning during subsequent shelf life. In this study, 'Nanguo' pears were cold-stored for different periods to elucidate the metabolism of phenylpropanoid accompanying browning. Changes in phenolics and flavonoids and the crucial enzyme activity and related gene expression involved in the phenylpropanoid pathway were monitored. It was found that the fruit that underwent long-term storage showed peel browning symptoms prior to softening, and the symptom got worse with increasing shelf life. Meanwhile, the accumulation of reactive oxygen species (ROS) and the decrease of ROS scavenging ability were noted. The content of phenolics and flavonoids and the activity and expression of shikimate dehydrogenase (SKDH), phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL) involved in the phenylpropanoid pathway decreased with prolonged storage. Correlation analysis revealed that browning was positively correlated with ROS accumulation, and the content of phenolics and flavonoids directly affected ROS scavenging ability. In addition, the decrease in phenolics and flavonoids might be owing to the reduced activity of SKDH, PAL, and 4CL and the down-regulated expression of PuPAL and Pu4CL . Collectively, this study indicated that the metabolism of phenylpropanoid is associated with the browning response induced by low-temperature stress. Highlights: Highly positive correlations were found between browning and ROS level. The content of phenolics and flavonoids directly affect ROS scavenging ability. Phenolics and flavonoids synthesis was associated with enzymes SKDH, PAL, and 4CL. Phenolics and flavonoids synthesis was associated with genes PuPAL and Pu4CL.