Fruits are an important source of a healthy diet due to their essential nutrients for daily intake. Melon is known as a significant fruit crop of the Cucurbitaceae family based on its various dietary benefits, but its shelf life needs to be maintained for long-term usage. 1-Methylcyclopropene (1-MCP) is a cyclopropene-derived synthetic plant growth regulator (PGR) that is used for significantly delaying the ripening process and maintaining the shelf life of climacteric fruits during storage. In this study, freshly harvested melon fruits were fumigated with various concentrations (1.0 µL·L⁻¹, 2.0 µL·L⁻¹, and 3.0 µL·L⁻¹) of 1-MCP treatment for 12 h (h) and stored at low temperature (8 ± 1 °C) for 30 days (d). The obtained results showed that 1-MCP fumigation coupled with low-temperature treatment maintains the postharvest shelf life of melon fruit. It was noticed that the increase in color hue (a* (red/green), b* (blue/yellow), L* (lightness)) was slowed down and the external fresh color was effectively maintained. At the same time, the firmness, soluble solids, titratable acids (TAs), and vitamin C (VC) content seemed to be maintained at a high level; weight loss and cell permeability were reduced; respiratory intensity and ethylene emission were inhibited; and the accumulation of superoxide anions and malondialdehyde (MDA) was also reduced. In addition, an upsurge in the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX) was noticed in melon fruits under the combined treatment of 1-MCP and low-temperature storage as compared with the control group (CK, without treatment), indicating that 1-MCP treatment can effectively enhance the antioxidant metabolism of melon fruits during storage. Overall, we can recommend that the 3.0 µL·L⁻¹ concentration of 1-MCP had the best effect on maintaining the internal and external quality of sweet melon fruit during storage.

Non-specific Lipid Transfer Proteins (nsLTPs) constitute a ubiquitous family of plant proteins that play a critical role in mediating plant adaptation and tolerance to abiotic stress. While their functions have been extensively characterized in model plants such as Arabidopsis thaliana and rice (Oryza sativa L.), they remain largely unexplored in Cucurbitaceae crops. We identified 31 CmnsLTP genes in the melon (Cucumis melo L.) genome, these genes were unevenly distributed across 11 chromosomes and classified into 8 subfamilies. Members of the same subfamily have similar gene structures and conserved domains, with all family members having motif 1 and motif 3. The promoter region contains cis elements that respond to light, hormones (ABA and MeJA response elements), and abiotic stress, suggesting that this gene is involved in melon growth, development, and stress response. Previous studies have identified copper resistant candidate MELO3C031073.2 through forward genetics, which belongs to the nsLTP family and was named CmnsLTPY.9 in this study. The RT qPCR results showed that the CmnsLTPY.9 exhibited specific expression in different tissues, The expression levels of CmnsLTPY.9 in leaves ranged from 0.3 to 3.2. Under copper stress, the ‘M625’ (copper-sensitive) showed a 3.2-fold increase, indicating marked upregulation. Additionally, CmnsLTPY.9 was localized to the endoplasmic reticulum, and the position remains unchanged after copper stress. This study provides the first systematic analysis of the CmnsLTP gene family in melon; these findings provide fundamental insights into their specific functions in plant development and stress response, as well as valuable genetic resources for future research on copper-tolerant molecular breeding.