Metalloid Nanomaterials Alleviate Arsenic Phytotoxicity and Grain Accumulation in Rice: Mechanisms of Abiotic Stress Tolerance and Rhizosphere Behavior

Nanoenabled agriculture technology exhibits potential in reducing arsenic uptake in rice; however, a systematic understanding of the rice-soil-microorganism process of nanomaterials (NMs) is lacking. Soil amendment of metalloid NMs, including SiO₂, hydroxyapatite, S⁰, and Se⁰ at 10-100 (0.1-5.0 for Se NMs) mg/kg, increased rice biomass by 76.1-135.8% in arsenic-contaminated soil (17.0 mg/kg) and decreased arsenic accumulation in plant tissues by 9.3-78.2%. The beneficial effects were nanoscale-specific and NMs type- and concentration-dependent; 5 mg/kg Se NMs showed the greatest growth promotion and decrease in As accumulation. Mechanistically, (1) Se NMs optimized the soil bacterial community structure, enhancing the abundance of <i>arsM</i> by 104.2% and subsequently increasing arsenic methylation by 276.1% in rhizosphere compared to arsenic-alone treatments; (2) metabolomic analyses showed that Se NMs upregulated the biosynthesis pathway of abscisic acid, jasmonic acid, and glutathione, with subsequent downregulation of the arsenic transporter-related gene expression in roots by 42.2-73.4%, decreasing the formation of iron plaque by 87.6%, and enhancing the arsenic detoxification by 50.0%. Additionally, amendment of metalloid NMs significantly enhanced arsenic-treated rice yield by 66.9-91.4% and grain nutritional quality. This study demonstrates the excellent potential of metalloid NMs for an effective and sustainable strategy to increase food quality and safety.