Exogenous Phytosulfokine α (PSKα) Alleviates Chilling Injury of Kiwifruit by Regulating Ca2+ and Protein Kinase-Mediated Reactive Oxygen Species Metabolism

Di Wang; Xueyan Ren; Lingkui Meng; Renyu Zheng; Dong Li; Qingjun Kong

doi:10.3390/foods12234196

Exogenous Phytosulfokine α (PSKα) Alleviates Chilling Injury of Kiwifruit by Regulating Ca²⁺ and Protein Kinase-Mediated Reactive Oxygen Species Metabolism

Foods. 2023 Nov 21;12(23):4196. doi: 10.3390/foods12234196.

Authors

Di Wang¹, Xueyan Ren¹, Lingkui Meng¹, Renyu Zheng¹, Dong Li², Qingjun Kong¹

Affiliations

¹ Xi'an Key Laboratory of Characteristic Fruit Storage and Preservation, Shaanxi Engineering Laboratory of Food Green Processing and Safety Control, College of Food Engineering and Nutritional Science, Shaanxi Normal University, Xi'an 710119, China.
² College of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China.

Abstract

Kiwifruit fruit stored at low temperatures are susceptible to chilling injury, leading to rapid softening, which therefore affects storage and marketing. The effect of 150 nM mL^-1 of exogenous phytosulfokine α (PSKα) on reactive oxygen species (ROS) metabolism, Ca²⁺ signaling, and signal-transducing MAPK in kiwifruit, stored at 0 °C for 60 days, was investigated. The results demonstrated that PSKα treatment effectively alleviated chilling injury in kiwifruit, with a 15% reduction in damage compared to the control on day 60. In addition, PSKα enhanced the activities and gene expression levels of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR), Ca²⁺-ATPase, and mitogen-activated protein kinase (MAPK). In contrast, the activities and gene expression levels of NADPH oxidase (NOX) were inhibited, leading to a lower accumulation of O₂^- and H₂O₂, which were 47.2% and 42.2% lower than those in the control at the end of storage, respectively. Furthermore, PSKα treatment enhanced the calmodulin (CaM) content of kiwifruit, which was 1.41 times that of the control on day 50. These results indicate that PSKα can mitigate chilling injury and softening of kiwifruit by inhibiting the accumulation of ROS, increasing antioxidant capacity by inducing antioxidant enzymes, activating Ca²⁺ signaling, and responding to MAPK protein kinase. The present results provide evidence that exogenous PSKα may be taken for a hopeful treatment in alleviating chilling injury and maintaining the quality of kiwifruit.

Keywords: Ca2+ signaling; PSKα; ROS metabolism; chilling injury; kiwifruit; protein kinase.

Grants and funding

This research was funded by the Fundamental Research Funds for the Central Universities (GK202207010), the Natural Science Basic Research Program of Shaanxi (2023-JC-QN-0272), and the Shaanxi Postdoctoral Fund (2023BSHEDZZ205).