Endophytic fungus Su100 enhances phosphorus solubilization and growth in sweet cherry via organic acids and metabolic reprogramming under phosphorus limitation

Phosphorus is an essential element for plant growth, but it is often present in the soil in an insoluble form, such as calcium phosphate (Ca₃(PO₄)₂), which greatly limits the efficiency of plant absorption and utilization. In this study, the endophytic fungus Su100 was found to significantly increase the solubilization efficiency of Ca₃(PO₄)₂ by secreting various organic acids, such as oxaloacetic acid, malic acid and fumaric acid. Transcriptomic analysis revealed that Su100 participated in the up-regulated expression of genes involved in glycolysis and tricarboxylic acid cycling in Ca₃(PO₄) - containing medium, thereby promoting organic acids biosynthesis and improving phosphorus solubilization. Further experiments showed that inoculation with Su100 promoted the growth of sweet cherry rootstock Gisela 6 seedlings under Ca₃(PO₄)₂ conditions. Furthermore, Su100 inoculation also promoted plant sugar and lipid metabolism, with increased expressions of related genes, indicating that Su100 enhanced sugar and lipid supply to support both plant growth and fungal activity. Meanwhile, fatty acid profiling confirmed increased levels of lignoceric acid, palmitic acid, heptadecanoic acid, stearic acid and other components. These results highlight the potential of Su100 as a biofertilizer to improve phosphorus uptake and sweet cherry growth under Ca₃(PO₄)₂ conditions. The study provides new insights into the molecular mechanisms of plant-fungus interactions and their role in sustainable agriculture.