Synergistic application of biostimulant and selenium nanoparticles enhances drought tolerance in potato through integrated physiological and transcriptomic modulation

Drought stress is a major constraint on global potato productivity, necessitating innovative mitigation strategies. This study investigates the potential of exogenous serotonin (5HT) and selenium nanoparticles (SeNPs), both individually and in combination, as biostimulants to enhance drought resistance in potato. Through integrated physiological, biochemical and molecular analyses, we demonstrate that while individual treatments provide moderate protection, the combined 5HT-SeNPs application significantly enhances water relations, photosynthetic efficiency and water use efficiency under drought conditions. The synergistic treatment achieved superior water retention, optimal osmotic adjustment and enhanced photosynthetic recovery compared to individual applications. Furthermore, 5HT and SeNPs synergistically strengthened antioxidant defenses by reducing H₂O₂ accumulation to control levels while maximizing enzymatic activities (SOD, CAT, POD) and promoting balanced osmolyte accumulation. Phytohormone profiling revealed that the combined treatment effectively modulates stress signaling by maintaining optimal ABA and IAA balance while enhancing SA and JA-mediated defense responses. Transcriptomic analysis identified extensive gene expression changes, indicating comprehensive metabolic reprogramming in photosynthesis, hormone signaling, phenylpropanoid biosynthesis and antioxidant pathways. Our findings provide novel insights into the synergistic mechanisms of 5HT and SeNPs-mediated drought tolerance and highlight their potential as an innovative, sustainable strategy to improve potato resilience in water-limited environments. • Serotonin and selenium nanoparticles synergistically enhance potato drought tolerance through integrated physiological mechanisms • Dual bio-stimulant treatment achieved optimal water retention and photosynthetic efficiency under water-limited conditions • Synergistic application effectively neutralized oxidative stress while enhancing enzymatic defense systems and osmotic regulation • Bio-stimulant combination optimized phytohormone networks and triggered coordinated gene expression reprogramming across metabolic and defense pathways