Integrated Physiological, Transcriptomic, and Metabolomic Analyses Reveal the Response Mechanisms of Selenium (Se) and Boron (B) Under Lead (Pb) Stress in Tobacco

Selenium and boron can alleviate lead (Pb) toxicity in plants, but their stress resistance mechanisms in tobacco remain unclear. The aim of this study was to investigate the effects of Se/B application on lead-induced oxidative stress, subcellular distribution, cell wall properties, and Pb accumulation. Additionally, a comprehensive analysis of transcriptomics and metabolomics data was conducted. Under Pb stress, the combined application of exogenous addition of Se, B and Se + B to a hydroponic system led to an increase in leaf biomass, promoted photosynthesis, increased antioxidant enzyme activity in tobacco, and significantly reduced the accumulation of Pb in the shoots of tobacco by downregulating the gene expression of the ABC transporter and upregulating the expression of aquaporin (AQP). Additionally, the application of Se and B increased the activity of the phenylpropanoid and glutathione metabolism pathways, promoting the synthesis of secondary metabolites such as coumarin, chlorogenic acid, ferulaldehyde, and (5-l-glutamyl)-l-amino acids. This, in turn, increased the tolerance of tobacco plants to Pb stress. Overall, our research findings provide new theoretical evidence regarding the roles of Se and B in alleviating Pb accumulation and offer potential strategies for the use of Se and B in the remediation of Pb-contaminated soils in agricultural production.