Spermidine enhances cold tolerance in tomato fruit by boosting antioxidant and energy metabolism synergy

Cold stress is a major factor affecting postharvest quality of tomato fruit. Although polyamine compounds have been widely used to enhance plant cold tolerance, direct evidence supporting spermidine (SPD) involvement in regulating tomato fruit cold resistance is still lacking. In this study, tomato fruits were treated by SPD or its inhibitor Methylglyoxal bis guanylhydrazone (MGBG), followed by storage at 4 °C, 25 °C, or a combination of both temperatures. Cold injury (CI) levels, along with relevant indices of the antioxidant and energy metabolism systems, were evaluated. The results showed that SPD significantly enhanced cold resistance in tomatoes by activating the antioxidant and energy metabolism systems. Furthermore, correlation analysis and transcriptome sequencing indicated a synergistic interaction between the antioxidant and energy metabolism systems, which jointly regulate cold tolerance in tomato fruit, with SPD further enhancing this synergy.