Metabolomic evaluation of selenium seed priming on mitigating lead stress toxicity in Vicia faba plants

Persistent lead contamination and the absence of natural remediation elements exacerbate the long-term toxicity of plants. Nevertheless, it has been consistently shown that selenium has a protective effect against heavy metal toxicity in plants. Consequently, it is imperative to identify the metabolic pathways that selenium employs to enhance the resistance of plants to lead stress. This study aimed to investigate the metabolomic alterations induced by selenium priming of Vicia faba seeds to enhance their tolerance to lead stress.

Selenium seed priming significantly improved the growth parameter and mitigated the adverse growth consequences observed under lead stress. Nuclear magnetic resonance-based metabolomic analysis identified 58 metabolites in the polar extracts of the shoots, with the metabolites composed of amino acids (40%), carboxylic acids (12%), fatty acids (11%), carbohydrates (5%), alkaloids (5%), and phenols (4%). The addition of Pb facilitated the biosynthesis of unique metabolites, including 2-methylglutarate, 3-methyladipate, and epinephrine, which were absent in control and selenium-treated samples. Conversely, 4-aminobutyrate and 2-methylglutarate were entirely absent in Pb samples. Selenium-treated plants accumulated trigonelline and AMP at levels 1.4 and 6.0 times, respectively, more than the control samples. Selenium-primed plants exposed to lead stress exhibited higher levels of asparagine, tryptophan, and xanthine compared to other treatments. As determined by both enrichment analysis and pathway analysis, the most significantly altered pathways were alanine, aspartate, and glutamate metabolism; aminoacyl-tRNA biosynthesis; and valine, leucine, and isoleucine biosynthesis pathways.

The results demonstrate the crucial role of selenium priming in enhancing the growth and lead stress resistance of Vicia faba plants by significantly altering the concentrations of key metabolites and metabolic pathways, particularly those involved in amino acid metabolism, offering a promising strategy for improving plant resilience to heavy metal contamination.