Transcriptome Analysis Reveals Root Endophyte Serendipita indica-Mediated Growth Promotion in Wheat Is Associated with Enhanced Photosynthesis

Serendipita indica (S. indica), a root endophytic fungus of the Sebacinaceae family, promotes growth and increases biomass accumulation in a wide range of plant species. However, the mechanism underlying S. indica-mediated growth promotion in wheat (Triticum aestivum L.), particularly its effects on chlorophyll accumulation, remains poorly understood. In this study, colonization by S. indica significantly enhanced shoot growth, biomass accumulation, plant height, fresh weight, dry weight and chlorophyll content in wheat seedlings. Transcriptome analysis revealed extensive transcriptional reprogramming in leaves, characterized by the upregulation of genes involved in chlorophyll biosynthesis and the downregulation of senescence-associated genes. Gene ontology (GO) enrichment analysis indicated that differentially expressed genes (DEGs) were predominantly associated with light-regulated developmental processes, whereas Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified significant enrichment in carotenoid biosynthesis and porphyrin metabolism pathways. These transcriptomic results were further validated by reverse transcription quantitative PCR (RT-qPCR), which confirmed the induction of chlorophyll biosynthesis-related genes and the repression of senescence-associated genes following S. indica colonization. Collectively, our results indicate that S. indica establishes a beneficial association with wheat and promotes chlorophyll accumulation through coordinated regulation of chlorophyll biosynthesis and leaf senescence, which may contribute to enhanced photosynthetic capacity and improved plant growth during the seedling stage.