Iron oxide nanoparticles alleviate cold stress in rice by reducing oxidative damage and enhancing antioxidant defense systems, and transcriptional networks

Cold stress significantly impairs the rice ( L.) growth and yield, particularly in temperate regions where abrupt temperature fluctuations often occur during the early growth stages. Given the need for novel strategies to improve crop cold tolerance, we evaluated the efficacy of iron oxide nanoparticles (FeO) in enhancing rice cold stress resilience. The plant nano-bionics strategy employs sub-12.5 nm iron oxide nanoparticles with a negative ζ-potential (− 37.6 mV), which achieve high colocalization within chloroplasts to confer cold tolerance in rice by enhancing photosynthetic efficiency and ROS scavenging. The reported mechanisms involve promoting plant growth and development, alleviating oxidative stress and inducing defense responses. Using RNA-seq, we analyzed the physiological and transcriptomic responses of rice to cold stress and Fe₂O₃ treatment. Under cold stress, the NPs elicited a strong antioxidant response-elevating superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities-which led to a marked reduction in oxidative damage, as shown by decreased ROS and MDA levels. Further, the NPs concurrently restored photosynthetic function and ameliorated cold-induced phenotypic damage. RNA-sequencing revealed that NPs application significantly alters a comprehensive transcriptomic reprogramming, enriching pathways for carbohydrate metabolism, photosystem, plant hormone signaling, and glutathione biosynthesis. Collectively, our findings establish that Fe₂O₃ nanoparticles ameliorate cold stress by preserving chloroplast structure, stomatal architecture, reduce oxidative stress marker, enhancing antioxidant defense system and stabilize photosystem, and providing a promising nanozyme-based approach for rice protection against cold induce damage.