Abstract
Cerium oxide nanoparticles (CeO(2)NPs) can boost crops' salt tolerance, yet their regulatory mechanisms in rice cultivars with contrasting salt tolerance remain unclear. This study investigated the regulatory differences in poly (acrylic acid)-coated nanoceria (PNC)-primed in salt-sensitive (Huanghuazhan, H) and salt-tolerant (Xiangliangyou900, X) rice. The results showed that PNC priming improved salt tolerance in two cultivars, but the underlying mechanisms differed. In the H cultivar, the enhanced tolerance was primarily attributed to enhanced photosynthesis (net photosynthesis and transpiration rates were 53.27% and 20.52% higher than the X cultivar); increased abscisic acid (ABA) content (up by 18.80% compared to the X cultivar), and activated stress-responsive signaling. Metabolomics further revealed that the differential metabolites were enriched in galactose metabolism, ascorbate, and aldarate metabolism, synergistically maintaining intracellular redox balance. In the X cultivar, PNC boosted reactive oxygen species' (ROS) scavenging capacity (catalase (CAT) increased 36.07%, H(2)O(2) and malondialdehyde (MDA) decreased 27.31% and 48.61% compared to H); elevated endogenous indole-3-acetic acid (IAA) and gibberellic acid3 (GA3) levels by 9.55% and 9.08%; and specifically activated cellular defense response and glutathione metabolism. Transcriptome analysis further revealed that the expression of IAA/GA3 signal-responsive genes (OsARGOS/OsGASR2) and antioxidant genes (OsCatA, OsAPX1) were significantly higher in the X cultivar than the H cultivar (p < 0.05), whereas the H cultivar showed higher expression of GST and ABA-related genes. This study provides a new perspective for the mechanism of PNC-enhanced salt tolerance in rice.