Proteomic and physiological insights into drought mitigation by exogenously applied calcium nanoparticles in Brassica napus

Drought stress poses a significant threat to rapeseed (Brassica napus) productivity. This study investigates the efficacy of calcium nanoparticles (Ca-NPs) in mitigating drought stress, with a specific focus on the proteomic reprogramming that underlies this resilience. Physiological assessments confirmed that Ca-NP application restored plant growth and biomass under drought conditions, correlating with enhanced photosynthetic efficiency and a potentiated antioxidant response. A pivotal and novel finding, revealed through non-invasive micro-test technology (NMT), was that Ca-NPs prevented drought-induced pathological leakage of cellular Ca²⁺, thereby stabilizing membrane integrity and suggesting a primed state for stress signaling. Quantitative proteomic analysis (TMT-based) identified significant alterations in the abundance of key proteins involved in central metabolic processes. Specifically, Ca-NPs upregulated proteins associated with carbon fixation, porphyrin and chlorophyll metabolism, and the glutathione-mediated antioxidant pathway, providing the first comprehensive proteomic evidence of a reconfiguration of primary and defensive metabolism in rapeseed under Ca-NP treatment. Furthermore, weighted protein co-expression network analysis (WGCNA) identified highly connected hub proteins within modules strongly correlated with improved physiological traits, pinpointing critical functional components of the drought response. These findings demonstrate that Ca-NPs do not merely alleviate symptoms but actively prime rapeseed plants by enforcing ionic homeostasis and orchestrating a protective proteomic landscape, positioning them as a powerful nano-priming strategy for sustainable agriculture. Moreover, exogenously applied Ca-NPs can be further used for rapeseed seed coating. The coated seeds are then applied in the precision drill-seeding of rapeseed, jointly promoting the increase in large-scale per-unit yield of rapeseed.