# PpSKα boosts chilling tolerance by activating PpTrxh9 in peach fruit

## TL;DR

This study shows that PpSKα helps peach fruits resist cold damage by boosting PpTrxh9 activity, reducing oxidative stress and chilling injury.

## Contribution

The novel finding is that PpSKα interacts with and phosphorylates PpTrxh9 to enhance cold tolerance in peach fruits.

## Key findings

- GB treatment increased PpTrxh9 and PpSKa expression, reducing oxidative injury in peach fruits.
- PpSKa overexpression in tomatoes reduced cold sensitivity, while its silencing in peaches worsened chilling injury.
- PpSKa phosphorylates PpTrxh9, linking its activity to improved cold tolerance in fruits.

## Abstract

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.

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.

Taken together, PpSKa decreased the development of CI by improving the expression of PpTrxh9 in peach fruits.