Cerium oxide nanoparticles ameliorate Arabidopsis thaliana root damage under UV-B stress by modulating the cell cycle and auxin pathways

Cerium oxide nanoparticles (CeO2-NPs) have been widely applied worldwide. In the field of agriculture, they have gained attention for their ability to promote seed germination, root elongation, and biomass accumulation in plants, as well as to increase plant resistance to various abiotic stresses. However, the underlying molecular mechanisms remain to be elucidated. Limited research has been conducted on whether CeO2-NPs can help plants mitigate damage caused by UV-B stress. In this study, Arabidopsis thaliana was selected as the research subject to investigate the effects of CeO2-NPs on the resistance of plant roots to UV-B stress at both the physiological and molecular levels. Our findings demonstrated that 120 mg/mL CeO2-NPs significantly alleviated UV-B-induced damage to the root system of Arabidopsis thaliana. Specifically, CeO2-NPs increased the activities of the root tip antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), reducing oxidative stress. The results from GUS staining and GFP fluorescence assays conducted on the transgenic lines CYCB1;1-GUS, DR5-GUS, QC25-GUS, and WOX5-GFP indicated that CeO2-NPs could increase the cell division activity, auxin accumulation, and stem cell niche activity of Arabidopsis thaliana root tips under UV-B stress. Furthermore, observations of GFP fluorescence in the transgenic lines PIN1-GFP, PIN2-GFP, and PIN7-GFP revealed that CeO2-NPs promoted root growth by inducing the accumulation of auxin transporters. Quantitative real-time PCR (qRT-PCR) analysis revealed that under UV-B stress, CeO2-NPs upregulated the expression of genes related to antioxidant enzymes, the cell cycle and auxin biosynthesis-related genes in Arabidopsis thaliana root tips while downregulating the expression of genes related to DNA damage repair and stress response. Therefore, CeO2-NPs have potential value for promoting plant growth and mitigating UV-B stress.