Nanoparticles enhance detoxification mechanisms to mitigate mercury stress in plants

Mercury (Hg) contamination threatens plant productivity and ecosystem stability due to its persistent mobility, complex biogeochemical cycling, and disruption of cellular homeostasis. Although nanoparticles (NPs) show potential for Hg mitigation, their effectiveness varies depending on NP chemistry, dose, soil properties, and plant responses. However, current reviews mainly describe individual NP applications or isolated detoxification pathways, while the mechanistic links among NP properties, Hg behavior, rhizosphere regulation, plant signaling, and multi-omics responses remain insufficiently integrated. This review establishes a mechanistic framework explaining how NP properties regulate Hg speciation, rhizosphere availability, plant signaling, and physiological recovery. Current evidence indicates that sulfur- and iron-based NPs primarily reduce Hg mobility through Hg-S interactions, adsorption, and mineral-associated stabilization, whereas silicon- and Zn-based NPs additionally enhance plant tolerance through physiological protection and stress regulation. Beyond direct Hg immobilization, NP-mediated tolerance involves rhizosphere processes, including microbial regulation, nutrient cycling, and Hg transformation, which influence plant exposure and detoxification efficiency. Cellular responses to NP application involve regulation of antioxidant systems, S metabolism, metal transport, and stress-responsive signaling pathways associated with Hg sequestration and redox balance. Multi-omics studies reveal that effective Hg tolerance depends on coordinated regulation among transcriptional responses, protein activity, and metabolic adjustment rather than activation of isolated pathways. However, knowledge remains derived from short-term laboratory experiments, with limited understanding of microbial interactions, post-transcriptional regulation, NP transformation and persistence, and ecological consequences. By integrating NP properties, Hg chemistry, rhizosphere regulation, plant signaling, and multi-omics responses, this review provides a mechanistic framework explaining why specific NPs produce Hg mitigation outcomes.