Phosphatidic Acid Serves as an Early Signaling Molecule Involved in Membrane Lipid Metabolism to Alleviate Postharvest Chilling Injury in Peach Fruit

Peach fruit develops chilling injury (CI) during cold storage, yet the symptoms are milder at 0 °C than at 5 °C; however, the underlying mechanism remains unclear. This study demonstrated that peach fruit stored at 0 °C maintains higher levels of structural phospholipids and membrane lipid unsaturation, along with lower activities of lipase and lipoxygenase (LOX), thereby alleviating membrane damage. Using lipidomics, we identified phosphatidic acid (PA) as a lipid closely associated with CI characteristics and revealed that it plays a signaling role at the early stage of storage at 0 °C, while its reduced levels at the later stage alleviate membrane damage, thereby participating in the regulation of CI in peach fruit. Moreover, at 0 °C, Phospholipase D (PLD) activity exhibited an initial increase followed by a decrease, which was consistent with the overall changes in PA content. During storage, PLD activity and PA content at 0 °C were significantly lower than those at 5 °C and 15 °C. These findings highlight the critical role of PA in temperature-dependent regulation and provide potential molecular targets for precise management of CI in the postharvest cold chain of peach fruit.