Upregulating photosynthesis-related genes of Cornus hongkongensis subsp. tonkinensis and demonstrating positive function of chtSGAT in salt tolerance

Although renowned for its ornamental value and extensive adaptability to heterogeneous environments, particularly in coastal saline-alkali region, the mechanism of salt tolerance in Cornus hongkongensis subsp. tonkinensis remains insufficiently explored. This study is to investigate the phenotypic, physiological, and transcriptomic responses of its seedlings exposure to a 0.3% salt solution for 55 days. Under the short-term salt stress (0-5 days), a significantly increment in proline content, while no significant responding in photosynthetic properties, were observed compared to the control (CK). However, after salt stress exceeded 30 days, superoxide dismutase (SOD) and the contents of osmotic regulators (soluble sugar, soluble protein and proline) significantly increased, along with a decline in photosynthetic efficiency. Through GO, KEGG, and WGCNA analyses, 12 candidate genes involved in chlorophyll synthesis, carotenoid biosynthesis, light-dependent reactions, Calvin cycle, and photorespiration were identified and found to be upregulated in the initial phase of salt stress. Amongst, transgenic Arabidopsis thaliana overexpressing chtSGAT exhibited enhanced seed germination rate and seedling growth under salt stress. The enhancement of F_v/F_m and F_v/F₀ ratios, antioxidant system, and osmotic regulators in transgenic lines, were alleviated ROS accumulation. These results suggest that chtSGAT tend to be a promising candidate gene for enhancing salt tolerance of C. hongkongensis subsp. tonkinensis. Our study provides theoretical support for the large-scale cultivation of dogwood seedlings in saline-alkali areas.