This study was performed to evaluate the effect of postharvest immersion in 1.0 g/L phenyllactic acid solution on the biosynthesis of anthocyanin and proanthocyanidin in winter jujube fruits. The results demonstrated that treatment with phenyllactic acid up-regulated the expression levels of transcription factors, including ZjMYB1R1, ZjMYB13/44/101, and ZjbHLH13/35/47/62. Conversely, it inhibited the expression levels of both ZjbHLH30 and ZjMYB30. Concomitantly, the gene expression levels of phenylalanine ammonialyase, 4-coumarate coenzyme A ligase, cinnamic acid-4-hydroxylase, chalcone isomerase, chalcone synthase, flavanone 3-hydroxylase, flavanone 3'-hydroxylase, anthocyanidin synthase, dihydroflavonol 4-reductase, UDP-glucose:flavonoid-3-O-glucosyltransferase 3, anthocyanidin reductase, and leucoanthocyanidin reductase were up-regulated by phenyllactic acid, resulting in the accumulation of anthocyanin and proanthocyanidin. Also, phenyllactic acid treatment reduced the accumulation of hydrogen peroxide. These findings suggest that phenyllactic acid promotes the biosynthesis of anthocyanin and proanthocyanidin in winter jujube fruits by enhancing the expression of key genes involved in their biosynthesis through the activation of bHLH and MYB transcription factors, thereby enhancing antioxidant capacity.

This study was undertaken to investigate the effects of exogenous melatonin on the activity and gene expression of cell wall-degrading enzymes and quality attributes (including mass loss rate, ethylene release rate and surface color) of ‘Nanguo’ pears during storage at room temperature. The results demonstrated that exogenous application of melatonin maintained higher flesh firmness, chlorophyll content and soluble solid content, remarkably decreased ethylene release rate, and delayed peel yellowing and the decrease in titratable acid content, but did not affect the mass-loss rate of ‘Nanguo’ pears. Moreover, melatonin treatment significantly retarded the degradation of water-insoluble pectin and the accumulation of water-soluble pectin. Compared with the control group, the most significant difference in the contents of water-insoluble and water-soluble pectin in the melatonin group appeared on days 3–12 and 6–12 (P < 0.05), respectively. On day 9, the content of water-soluble pectin in the control group was 1.18 times higher than that in the melatonin group, while the content of water-insoluble pectin in the melatonin group was 1.21 times higher than that in the control group. The changes of the content of pectin substances were related to the inhibition of melatonin on polygalacturonase (PG), pectin methylesterase (PME), β-glucosidase (β-glu), cellulase (Cx) activities and gene expression. These results demonstrated that exogenous application of melatonin could maintain the fruit quality of ‘Nanguo’ pears by inhibiting the activity and gene expression of cell wall-degrading enzymes and ethylene release.

Ginger rhizomes are subject to mechanical damage during harvest, handling, and transportation, and ethephon has been reported to promote plant wound healing. In this study, the effect and mechanism of ethephon treatment after harvest on wound healing in ginger rhizomes were investigated. The results indicated that 50 mg/L ethephon treatment retarded mass loss, and enhanced the contents of hydrogen peroxide, total phenolic compounds and lignin in ginger rhizomes during the wound healing process. The activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) involved in reactive oxygen species (ROS) metabolism were increased in the ethephon-treated ginger rhizomes. The accumulation of phenolic compounds and lignin during wound healing were correlated with a significant increase in peroxidase (POD) and phenylalanine ammonia lyase (PAL) activities. These findings suggest that ethephon treatment can promote the wound healing process of ginger rhizomes by modulating key enzyme activities involved in ROS metabolism and the phenylpropanoid pathway to enhance antioxidant capacity and accumulate secondary metabolites.

eaches are subject to flesh softening during postharvest storage and transport, which affects the storage life of the fruit and causes huge economic losses. Previous research has demonstrated that postharvest brassinolide treatment can maintain flesh firmness, ascorbic acid and soluble solids contents, and enhance disease resistance in peach fruits. This study assessed the influence of postharvest brassinolide treatment on the expression of key genes involved in cell wall degradation and the phenylpropanoid pathway in peach fruits by real-time fluorescence quantitative polymerase chain reaction (qPCR). The results showed that brassinolide dipping inhibited the gene expression of pectate lyase 1, polygalacturonase 21 and pectin methylesterase 1, and significantly enhanced the gene expression of peroxidase, cinnamoyl-CoA reductase, phenylalanine ammonia lyase and caffeoyl-CoA-O-methyltransferase 5 in peach fruits. It also increased the gene expression levels of chaleone synthase, chaleone isomerase, dihydroflavonol-4-reductase and flavanone 3-hydroxylase at the early stage of storage. These findings imply that brassinolide can suppress the expression of key genes involved in cell wall degradation and enhance the expression of key genes involved in the phenylpropanoid pathway, thereby delaying peach fruit softening and enhancing disease resistance.