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Chilling injury (CI) often occurs in postharvest peach fruit during low-temperature storage, and exogenous melatonin (MT) treatment has been demonstrated to alleviate CI in cold-stored peach fruit. In this study, we further investigated the effect of MT treatment on DNA methylation in relation to the chilling-induced browning in cold stored peaches. The results revealed that MT treatment upregulated PpPAL expression while simultaneously suppressing the transcripts of PpPPO and PpPOD. This dual effect resulted in the increased accumulation of phenolics, effectively reducing the incidence of browning in peaches stored at 4 °C. In addition, MT treatment increased the activities of methylesterase and demethylase, affecting significant changes in the DNA methylation levels of the local genes PpPPO , PpPOD and PpPAL , which suggested that MT treatment could mediate DNA methylation of the browning-related genes such as PpPPO , PpPOD and PpPAL , and consequently increased the phenolic contents and alleviated browning symptoms in cold-stored peaches. • MT treatment reduced chilling-induced browning in peaches. • MT increased the accumulation of phenolics in peaches. • MT upregulated PpPAL expression while suppressed the transcripts of PpPPO and PpPOD. • MT treatment increased the activities of methylesterase and demethylase. • MT regulated the DNA methylation levels of the local genes PpPPO , PpPOD and PpPAL. [ABSTRACT FROM AUTHOR]

The effects of indoleacetic acid (IAA) treatment on chilling injury and endogenous phytohormones in peach fruit were studied. The results showed that IAA treatment decreased chilling injury index of cold-stored peaches, effectively maintaining fruit firmness and reducing the electrical conductivity level. IAA treatment upregulated the expression of IAA biosynthetic gene PpMES and signaling pathway gene PpSAUR , but reduced the transcript abundance of IAA degradative genes PpDAO , PpGH3 , and PpIAMT , leading to endogenous IAA accumulation in treated peaches. Meanwhile, after IAA treatment, contents of melatonin and γ-aminobutyric acid (GABA) were also increased which was associated with the upregulation of their anabolic genes and downregulation in GABA catabolic genes. In addition, the levels of abscisic acid (ABA) and gibberellin (GA) were reduced in treated peaches due to its modification in the transcript levels of ABA and GA metabolic genes. Collectively, IAA could alleviate the symptoms of chilling injury in peach fruit via regulating contents of endogenous phytohomones such as IAA, melatonin, GABA and GA. • IAA treatment reduced chilling injury and maintain fruit quality in peaches. • IAA induced endogenous IAA content in harvested peaches. • IAA increased melatonin and GABA contents in harvested peaches. • IAA inhibited ABA and GA contents in harvested peaches. [ABSTRACT FROM AUTHOR]