Hot water treatment improves peach fruit cold resistance through PpHSFA4c-mediated HSF-HSP and ROS pathways

Peach fruit is cold-sensitive and susceptible to chilling injury (CI), and hot water (HW) treatment can reduce their CI. However, the mechanism of HW treatment reduced CI has not been characterized. In this study, HW treatment suppressed the increases in CI index, electrolyte leakage, and malonaldehyde (MDA) content in peach fruit during cold storage. It also decreased reactive oxygen species (ROS) accumulation and increased the activity of ROS-scavenging enzymes. Transcriptome analysis indicated that HW treatment might contribute to the crosstalk between the heat shock factor-heat shock protein (HSF-HSP) and ROS pathways during cold storage. PpHSFA4c was a key transcription factor and could up-regulate defense genes to alleviate the CI of peach fruit during storage. Furthermore, PpHSFA4c could activate the expressions of PpHSP18.5, PpHSP70, PpHSP83, PpAPX1, and PpAPX3 by interacting with their promoters. These studies indicated that HW treatment alleviated the CI, increased antioxidant activity, and maintained ROS homeostasis of peach fruit through the PpHSFA4c-mediated HSF-HSP and ROS pathways. This study provides novel insights into the regulatory mechanisms of HW treatment alleviating CI in postharvest peach fruit, and expands the theoretical basis for commercial application of HW treatment technology to maintain quality and reduce CI in cold-sensitive fruit.