A metabolomic, transcriptomic profiling, and mineral nutrient metabolism study of the phytotoxicity mechanism of uranium

Uranium (U) is a nonessential element that is readily adsorbed and retained in plant roots, causing root damage plants, rather than being translocated to other parts of the plant. The phytotoxicity mechanism of U is poorly understood. In this study, Vicia faba, a model plant for toxicological research, was selected as experimental material to investigate the phytotoxicity mechanism of U. In this study, the effects of U on the growth and development, methonome, transcriptome and mineral nutrient metabolism of V. faba were studied under different U treatments (0–25 μM) by integrating metabolomics, transcriptomic, and mineral nutrient metabolism analysis techniques. The results showed that U accumulation in roots and aboveground parts reached 164.34–927.90 μg/pot, and 0.028–0.119 μg/pot, respectively. U was mainly accumulated in the cell wall of roots, which damaged the root microstructure and inhibited root growth and development. In terms of mineral nutrient metabolism, U treatment (0–25 μM) led to changes in mineral metabolic profiles of seedlings. In total, 612 different metabolites were identified in nontargeted metabolomics, including 309 significantly upregulated metabolites and 303 significantly downregulated metabolites. Using RNA-seq, 4974 differentially expressed genes (DEGs) were identified under the high-concentration U treatment (25 μM), including 1654 genes significantly upregulated genes and 3320 genes significantly downregulated genes. Metabolic pathway analysis showed that a high concentration of U led to an imbalance of mineral nutrient metabolism in plants and changes in the metabolism and transcriptome pathway of plants, including alterations in the function of plasmodesmata and auxin signal transduction pathway. The latter finding may potentially explain the toxic effect of U on plant roots.