Muti-omics insights the enhancement of drought tolerance in sweet cherry with dark septate endophyte S16.

Drought stress severely limits the growth and productivity of sweet cherry (Prunus avium L.). Dark septate endophytes (DSEs) are a group of root-associated fungi known to enhance plant stress tolerance. This study aimed to explore the role of DSE fungus S16 in improving drought tolerance in sweet cherry seedlings and to reveal the underlying molecular and microbial mechanisms through a multi-omics approach. Physiological analysis showed that S16 inoculation improved plant growth, increased relative water content, photosynthetic rate, and antioxidant enzyme activities, while reducing ion leakage and oxidative damage under drought conditions. Metabolomic and transcriptomic analyses identified key metabolic pathways, particularly flavonoid and phenylpropanoid biosynthesis, as being significantly activated, with upregulation of genes such as PAL, 4CL and CHS, and increased accumulation of metabolites like cinnamic acid (CA) and flavonoid derivatives. Exogenous application of CA at 0.5 mM further enhanced drought resistance by reducing reactive oxygen species (ROS) levels, increasing proline accumulation, and boosting antioxidant enzyme activities. Rhizosphere microbiota analysis revealed that S16 symbiosis and CA treatment under drought conditions increased the abundance of beneficial bacteria, such as members of Sphingomonas, Stenotrophobacter and Parcubacteria, while promoting the dominance of Humicola and Fusarium fungi. These findings provide multi-omics evidence for the role of S16 in enhancing drought tolerance in sweet cherry, offering a theoretical basis for the application of DSE fungi in sustainable fruit tree production.