Priming tomato with AgNPs coated with Pseudomonas N5.12 metabolites enhances plant resilience to drought stress

Introduction Under current climate change conditions, agronomic yield is compromised by limited water availability and sudden drought events throughout the plant cycle. Among the tools to overcome drought stress, beneficial bacteria have been used in agriculture as biofertilizers, but the potential of bacterial metabolites has been increasingly underscored. Furthermore, bacterial metabolites can be formulated into nanoparticles (AgNPs) to further improve their activity. Methods Tomato plants were treated with biogenic silver nanoparticles or bacterial metabolites derived from Pseudomonas N5.12 and exposed to drought stress (via foliar spray or soil drench). Physiological and biochemical parameters, including photosynthetic performance, pigment content, oxidative stress markers, and antioxidant enzyme activities, were evaluated. Transcriptome analysis was also performed to assess the whole-plant response to drought under the different treatments. Results Drought stress significantly reduced tomato shoot length (−14.4%), fresh weight (−30.8%), and dry weight (−29.5%); increased H 2 O 2 content (18.2%); and altered antioxidant enzyme activities. Pretreatment with AgNP (NPs coated with Pseudomonas N5.12 metabolites, 60 ppm) improved shoot length (11.5%), fresh weight (49.3%), and dry weight (50.1%) under drought conditions. AgNPs increased transpiration without affecting net photosynthesis and induced oxidative signaling, as indicated by increased H 2 O 2 (18.5%) and MDA (14.1%) levels, along with enhanced SOD activity (66.5%). Transcriptomic analysis revealed a distinct AgNP-induced gene expression profile. Approximately 50% of the differentially expressed genes were encoded in chloroplasts and mitochondria and were primarily related to protein synthesis, photosynthesis, and energy metabolism. Conclusion AgNPs coated with Pseudomonas N5.12 metabolites enhance drought tolerance in tomato by improving growth, modulating redox homeostasis, and inducing extensive organelle-associated gene reprogramming. These findings demonstrate the advantages of nanoparticle-based formulation of bacterial metabolites. Overall, AgNPs show strong potential as a tool to support crop growth under drought conditions.