Molecular mechanism of silver nanoparticles inhibiting primary root growth of Oryza sativa L

Abstract

Elucidating the phytotoxicity of silver nanoparticles (AgNPs) at the primary tissue level is essential for a comprehensive assessment of their ecotoxicological risks. This study systematically investigated the phytotoxic mechanisms of polyethyleneimine-coated silver nanoparticles (AgNPs@PEI) on plant primary roots using rice (Oryza sativa L.) primary roots as an experimental model through integrated physiological, transcriptomic, and metabolomic analyses. Exposure to AgNPs@PEI induced concentration-dependent growth inhibition, with a 10 mg L⁻¹ treatment causing a 44% reduction in root length, a 50% decrease in biomass, and a 28.3% shortening of the root meristematic zone, accompanied by abnormal root hair development and cap detachment. Physiological assessments revealed significant disturbances in root vitality and antioxidant enzyme activities (SOD, POD, and CAT). Transcriptomic profiling identified significant downregulation (fold change > 2) of genes involved in nine key metabolic pathways, most notably phenylpropanoid biosynthesis, aromatic amino acid (phenylalanine/tyrosine/tryptophan) biosynthesis, and glutathione metabolism. Metabolomic analysis revealed concomitant disruptions in seven essential pathways, particularly those involved in unsaturated fatty acid biosynthesis. These transcriptomic and metabolic alterations collectively impaired cell wall lignification through suppression of the phenylpropanoid pathway and compromised membrane integrity via dysregulation of fatty acid metabolism. This research elucidates the phytotoxic effects of AgNPs from a primary plant tissue perspective, providing novel evidence for understanding nanomaterial–plant interactions at the tissue level.