The effects of root-specific overexpression of CmDUF1 on the gene expression of melon seedlings under heat stress

High temperature stress is one of the critical environmental factors affecting the growth and yield of melons. Enhancing the heat tolerance of melons is essential for ensuring stable production in high-temperature environments. In recent years, genetic engineering techniques have shown great potential in improving crop resilience to stress. The overexpression of the CmDUF1 gene has been found to enhance salt tolerance in melons; however, its effect on the heat tolerance of melon seedlings remains unknown. This study aims to investigate the impact of the CmDUF1 gene on the heat tolerance of melons and its underlying mechanisms. By transforming a CmDUF1 gene overexpression vector into the root system of melons, we obtained melon seedlings with overexpressed CmDUF1 (OEDUF1), which were subjected to heat stress treatment. The results demonstrated that under heat stress conditions, the suppression rates of fresh weight and dry weight for both the aerial parts and root systems of OEDUF1 were significantly lower than those of the control group, indicating that the overexpression of the CmDUF1 gene significantly enhances heat tolerance in melons. Additionally, one day after heat stress, the contents of antioxidant enzymes (SOD, POD, CAT, APX, and GR) in OEDUF1 significantly increased, while malondialdehyde (MDA) levels significantly decreased. The proline (PRO) content and the activity of its synthesizing enzyme (P5CS) also significantly rose, whereas the activity of proline dehydrogenase (ProDH) decreased significantly. Further transcriptomic and qPCR quantitative analyses revealed that the overexpression of the CmDUF1 gene significantly upregulated the expression of antioxidant enzyme-related genes (such as CmCSD1, CmPOD1, CmCAT2, CmAPX1, and CmGR1) and proline-related genes (such as CmP5CS). Moreover, the expression levels of heat shock protein (HSP) genes (including CmHSP17.6II, CmHSP17.6C, and CmHSP18.2) were also significantly elevated. In summary, the CmDUF1 gene enhances the heat tolerance of melons by promoting the expression of antioxidant enzyme-related genes and proline-related genes, increasing antioxidant enzyme activity and proline content, and enhancing the expression of heat shock protein genes. This study not only provides a reference for the application of CmDUF1 in heat tolerance breeding of melons but also enriches our understanding of the molecular mechanisms by which DUF regulates plant heat tolerance.