CpCOR1 gene positively regulates cold tolerance and antioxidant activity of papaya fruit under postharvest cold shock treatment

Abstract

Inappropriate low temperatures can induce harmful effects on post-harvest papaya fruit, a phenomenon known as "chilling injury." This study aims to elucidate the role of CpCOR1, a gene encoding a cold-regulated protein, in the manifestation of low temperature-induced chilling injury in papaya fruit. Our results demonstrate that cold shock treatment (CST, 2 ℃ ice-water for 0.5 h) significantly reduced the chilling injury index (CII), concurrently preserving the cell microstructure and mitigating the increase in cell membrane permeability during both 5 ℃ and 25 ℃ storage. Transcriptome analysis and qRT-PCR revealed a substantial up-regulation of the CpCOR1 gene in CST papaya fruit compared to the control fruit. Furthermore, bioinformatics and phylogenetic tree analysis identified CpCOR1 as a basic hydrophobic protein with a coding sequence of 606 bp and an amino acid sequence of 201 aa, classifying it under the COR413 subgroup. Sub-cellular localization assays confirmed that CpCOR1 is primarily localized to the cell membrane. Moreover, overexpression of CpCOR1 in tobacco leaves and papaya fruit significantly alleviated chilling injury symptoms, suppressed yellowing, reduced malondialdehyde (MDA) accumulation, and maintained higher activities of antioxidant enzymes, including catalase (CAT) and ascorbate peroxidase (APX), compared to the control group. In summary, our findings suggest that cold shock treatment is an effective strategy to retard the onset of low-temperature damage, with CpCOR1 playing a pivotal role in enhancing cold resistance and delaying ripening by activating antioxidant activity in papaya fruit.