Abstract
INTRODUCTION: The cold chain system is extensively used to lower the quality deterioration in postharvest fruits. However, the occurrence of chilling injury (CI) is a common phenomenon in peach fruits, consequently compromising their market value. METHODS AND RESULTS: Cold tolerance was boosted by glycine betaine (GB) supplementation. GB treatment promoted the thioredoxin h9 (PpTrxh9) expression and ameliorated oxidative injury. Using assays such as yeast two-hybrid, co-immunoprecipitation, pull-down, and bimolecular fluorescence complementation, SHAGGY-related protein kinase a (PpSKa) was verified as a protein interacting with PpTrxh9. GB treatment elevated the PpSKa expression. The overexpression of PpSKa in tomato fruits decreased the cold sensitivity and oxidative damage, whereas virus-induced gene silencing of PpSKa in peach fruits aggravated the CI progression and oxidative damage. PpSKa was found to phosphorylate PpTrxh9 in the kinase assay. Moreover, PpSKa-overexpressed tomato fruits exhibited higher SlTrxh9 expression, whereas the PpSKa-RNAi peach fruit exhibited lower PpTrxh9 expression. DISCUSSION: Taken together, PpSKa decreased the development of CI by improving the expression of PpTrxh9 in peach fruits.