Integrative multi-omic analyses reveal the molecular mechanisms of silicon nanoparticles in enhancing hyperaccumulator under Pb stress

Lead (Pb), one of the most ubiquitous and harmful contaminants of farmland, seriously threatens soil health and food security. Silicon nanoparticles (SiNPs) have potential applications in soil remediation and phytoremediation. Yet, how SiNPs influence plant growth under Pb stress remains poorly understood. In this study, the candidate Pb-hyperaccumulator Lolium multiflorum was selected to investigate the toxicity of Pb and the mitigation of Pb stress by SiNPs. The application of SiNPs was able to enhance Pb enrichment and maintain proper photosynthesis and root growth of L. multiflorum. Transcriptomic and metabolomic analyses indicated that Pb exposure interfered with nitrogen metabolism and alanine, aspartate and glutamate metabolism pathways in roots, which changed the root exudate composition. Besides, SiNPs altered both the accumulation of metabolites and correlated gene expression in roots, further affecting root exudates and stimulating the defense system, consequently increasing Pb tolerance. Our findings both demonstrated that co-application of L. multiflorum with SiNPs has potential for phytoremediation of Pb-polluted soil and revealed the contributions of SiNP amendment to mitigating Pb toxicity, and provided a new strategy for phytoremediation of farmland ecosystems.