Heat acclimation reduces postharvest loss of table grapes during cold storage – Analysis of possible mechanisms involved through a proteomic approach

• Hot water treatment effectively reduces postharvest losses of grape berries.
• Proteomic analysis reveals 64 differentially expressed proteins upon heat treatment.
• Proteins involved in defense responses are up-regulated by heat treatment.
• Proteins related to carbohydrate and energy metabolism are induced by heat treatment.

In this study, a combined biochemical and proteomic approach was used to investigate changes of fruit quality and protein expression profiles of grape berries upon hot water treatment (HWT) during the subsequent 45 days of cold storage. HWT obviously inhibited postharvest loss and chilling damage by reducing weight loss and membrane damage and slowing fruit softening. Proteomic analysis allowed the identification of 64 proteins regulated by heat treatment. Most of the up-regulated proteins in heat-treated grape berries were related to defense response and redox metabolism, suggesting a physiological adaptation to environmental stress. In addition, the increased expression of proteins associated with carbohydrate and energy metabolism immediately after HWT provided a molecular explanation for the rapid decline of soluble sugar content observed in heat-treated grape berries, which might be necessary for activation of the energy-demanding defense response to storage environmental stress, thereby reduced postharvest loss during storage at low temperature.