The CmCt gene induced reversibility of copper toxicity in melon

Copper is crucial for plant growth and development, but excess copper can damage the leaves of melons.We constructed a genetic population using M625 (copper sensitive) and M972 (copper tolerant) materials for precise localization. Under copper stress, we quantified the levels of reactive oxygen species (ROS), antioxidant enzyme activities, hormone contents, copper accumulation, and conducted a detailed examination of leaf structural characteristics. Bulk segregant analysis sequencing (BSA-seq) revealed that the CmCt gene was located within a 1.2 Mb interval on chromosome 5. The initial localization interval was 166.86 kb, and this interval was shortened to 29.05 kb after the analysis of 1200 F₂ individuals. There were a total of 6 genes in the interval, among which only MEL03C031073.2 (CmCt, Cucumis melo Copper tolerance) encodes a nonspecific lipid-transfer protein-like protein with non synonymous mutations. We further investigated and found that the gene is subcellular localized in the endoplasmic reticulum (ER), and its changes in the natural population (copper sensitivity and copper tolerance) are consistent with those of the parents. The results of the relevant physiological and biochemical indices of the parental plants subjected to copper stress (2 g/L) indicated a gradual increase in the levels of ROS, malondialdehyde (MDA), jasmonic acid (JA), and salicylic acid (SA). Concurrently, peroxidase (POD) activity exhibited an increase, while the activities of catalase (CAT) and superoxide dismutase (SOD) initially rose before subsequently declining. Moreover, there are differences in cellular structure between copper tolerant and copper sensitive melons, and copper tolerant materials exhibit stronger antioxidant defense capabilities.