Pyruvic acid improves cold-storage quality of plum fruit by stimulating cyanide-resistant respiration and regulating sugar metabolism

The current study investigates the impact of pyruvic acid (PA) as an activator of cyanide-resistant respiration (CRR) on enhancing the cold tolerance of post-harvest plum fruit (cv. 'Dazi'), and explores the underlying mechanism. Using distilled water as a control treatment, the plum fruits were soaked separately in solutions of 1 mM, 5 mM, and 10 mM PA and stored at 4 ℃, with the degree of chilling injury (CI) evaluated every 6 days. Fruits treated with 5 mM PA exhibited a much reduced rate and index of CI. The treatment with 5 mM PA enhanced the activity of alternating oxidase (AOX) and the relative expression of PsCBF2 of fruits. Although the activity of sucrose synthase (EC 2.4.1.13) I decreased after treatment, the content of sucrose and fructose increased due to the elevated activities of sucrose synthase (EC 2.4.1.13) II, NAD+-sorbitol dehydrogenase (EC 1.1.1.14), and NADP+-sorbitol dehydrogenase (EC 1.1.1.B60), resulting in improved flavor, particularly sweetness. The correlation of CI index, AOX activity, relative expression of PsCBF2 and sugar metabolism of fruits was strengthened by treatment. The present findings demonstrate that treatment with 5 mM PA could enhance the cold-storage quality of plum fruit by inducing CRR to regulate sugar metabolism, while also involving PsCBF2 in regulatory.