Vaccinating radish with CeO₂ nanoparticles: a nano-priming strategy to activate systemic defense against atmospheric...

Atmospheric deposition represents a significant source of cadmium (Cd) in agricultural lands, leading to unintended consequences for crop production and food safety. Here, we proposed that nanoparticles may serve as "pre-priming agents" to enhance plant resistance against Cd stress. Specifically, we investigated the pre-priming potential of CeO₂-NPs in improving the resistance of cherry radish (Raphanus sativus L.) to simulated atmospheric deposition of CdCl₂ and CdS-NPs. Exposure to atmospheric Cd at 0.5 mg/d/plant reduced plant biomass by 13.4-30.5% and increased crude fiber content by 11.1-85.3%, with CdCl₂ exhibiting greater phytotoxicity than CdS-NPs. Cd exposure predominantly caused oxidative damage in plant tissues, as evidenced by a 13.7% to 49.3% increase in malondialdehyde (MDA) levels. However, pre-exposure to CeO₂-NPs significantly mitigated these adverse effects, promoting plant growth and quality, and reducing Cd accumulation in leaves by 46.1-60.5% and in fruits by 26.2-32.4%. Notably, the pre-priming effect of CeO₂-NPs was linked with the early activation of reactive oxygen species (ROS) signaling in both leaves and fruits, accompanied by a 1.04- to 1.32-fold increase in glutathione levels. Transcriptomics further revealed that CeO₂-NPs activated key signaling pathways related to plant hormone signal transduction and MAPK cascades, facilitating co-modulation from top-down regulation. This pre-activated defense mechanism effectively modulated genes associated with energy and nitrogen metabolism, detoxicants biosynthesis, and ionic transporter regulation, thereby enhancing resistance capability while restricting Cd uptake. These findings demonstrate the potential utility of CeO₂-NPs as effective pre-priming agents for initiating defensive responses throughout plants; thus, establishing nano-enabled priming as a sustainable strategy for mitigating atmospheric Cd contamination within agricultural systems.