Mn-doped cerium dioxide nanozyme mediates ROS homeostasis and hormone metabolic network to promote wheat germination under low-temperature conditions

Nanozymes are a class of nanocatalytic materials that mimic the functions of natural enzymes. Their enzyme-like properties enable the catalytic scavenging of excess reactive oxygen species (ROS) generated in plants under abiotic stress, thereby alleviating oxidative stress. Research on nanozymes’ role and related mechanisms in alleviating low-temperature stress in crops is still unclear. Therefore, developing nanozymes that enhance early stage cold tolerance in crops is critical for maintaining agricultural production and global food security. We synthesized a nanozyme with catalase (CAT)-like activity, manganese-doped cerium oxide (MCNPs) nanoparticles. This study demonstrates that priming with MCNPs significantly accelerated wheat germination under cold stress, increasing the germination index by 7.1% and seedling biomass by 6.2–17.2% compared to hydropriming. Through SP–ICP–MS analysis, we confirmed that MCNPs can enter the seed. We also found that the catalase-like activity of MCNPs synergistically enhanced endogenous antioxidant enzymes (CAT and superoxide dismutase) to effectively eliminate excessive ROS in wheat seeds. Further analysis using LC–MS and qPCR showed that this ROS homeostasis influenced hormone metabolism by regulating the expression of genes involved in the hormone metabolic network, elevating growth-promoting hormones (gibberellin and ethylene) by 25.5–27.2% while suppressing stress-responsive hormones (jasmonic acid and abscisic acid). Subsequent activation of the gibberellin-responsive transcription factor TaGAMYB up-regulated amylase genes, boosting β-amylase activity by 17.1–18.5% and accelerating starch hydrolysis into reducing sugars, collectively enhancing low-temperature germination. MCNP priming significantly alleviated the inhibitory effects of low temperature on wheat seed germination by coordinately regulating the processes of “ROS homeostasis,” “hormone metabolism,” and “starch hydrolysis,” offering a promising strategy for enhancing plant cold tolerance and maintaining food security in the face of climate change.