Identification of xylanase (CpXYN1) gene and its role in promoting pulp softening during papaya fruit storage

• 1-MCP treatment delayed papaya fruit softening by suppressing endoxylanase activity. • CpXYN1 contains an open reading frame of 2760 nucleotides encoding 919 amino acids. CpXYN1 has a close evolutionary relationship to XYNs in durian and cocoa. • CpXYN1 is localized in cell wall and highly expressed in roots and ripened fruit. • OE- CpXYN1 reduces papaya fruit firmness by promoting CpXYN1 expression and activity. Postharvest papayas ( Carica papaya L.) often soften and decay, leading to significant fruit wastage. Endoxylanase (XYN) plays a role in the modification of xylan or arabinoxylan, and its activity has been related to papaya softening. In this study, we evaluated the effects of 1-Methylcyclopropene (1-MCP) treatment (1.0 µL·L⁻¹ for 24 h) on the softening physiology of papaya, and explored the molecular function of the CpXYN1 gene in regulating fruit softening. The results showed that 1-MCP treatment significantly maintained fruit firmness, chewiness, and hemicellulose content, while suppressing the activities of cellulase (CX), polygalacturonase (PG), and XYN compared to the control. Characterization and phylogenetic analysis revealed that CpXYN1 contains an open reading frame of 2760 nucleotides encoding 919 amino acids, with a close evolutionary relationship to XYNs in durian and cocoa. Subcellular localization indicated that CpXYN1 is localized in the cell wall. RT-qPCR analysis demonstrated that CpXYN1 is highly expressed in roots and ripened fruit. Furthermore, transient overexpression of the CpXYN1 gene significantly increased CpXYN1 activity, resulting in reduced hemicellulose content, firmness, and chewiness in both control and 1-MCP-treated papayas. These findings suggest that CpXYN1 may function as a positive regulator of fruit softening and ripening during papaya storage. This study provides practical insights into controlling fruit softening and extending shelf life by targeting CpXYN1 in postharvest papaya.