Seed Priming with Silver Ions Decreased Cadmium Absorption by Wheat Grains via Reactive Oxygen Species Generation

Seed Priming with Silver Ions Decreased Cadmium Absorption by Wheat Grains via Reactive Oxygen Species Generation
Chenghao Ge1, Yixuan Wang1, Dongmei Zhou1*,
1 State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China
Contact Email: gech@nju.edu.cn
Tel: 13011701863

Abstract: Cadmium (Cd) contamination in wheat grains poses a serious threat to human health, making the development of low-cost and environmentally friendly strategies to reduce Cd accumulation in wheat a critical need. In this study, we demonstrate that priming wheat seeds with silver ions (Ag⁺) leads to the in-situ formation of silver nanoparticles (AgNPs), which function as ROS-generating nanoparticles to improve tolerance to Cd stress across seed, seedling, and mature plant stages. Seeds treated with 0.11 mg L⁻¹ Ag⁺ showed the highest hydrogen peroxide (H₂O₂) levels and the lowest tissue Cd concentrations during seedling growth. The application of diphenyleneiodonium chloride (DPI) during Ag⁺ priming suppressed H₂O₂ production and resulted in increased Cd uptake in seedlings. Notably, elevated H₂O₂ levels were maintained even during the grain-filling period in Ag⁺-primed plants. Transcriptomic analysis revealed that Ag⁺ priming induces extensive transcriptional reprogramming in wheat. KEGG pathway enrichment combined with quantitative real-time PCR indicated activation of stress-signaling and metal-absorption-related pathways, including plant hormone signal transduction and the MAPK signaling pathway. Furthermore, Ag⁺ priming modulated the expression of key Cd-related genes, downregulating the Cd transporter gene TaABCB11, while upregulating vacuolar sequestration genes (TaABCC9 and TaHMA3) and the cellular Cd export gene TaTM20. These changes suggest that Ag⁺ priming triggers a ROS-mediated stress response, establishing a “stress memory” that persists throughout the growth cycle, enhances Cd tolerance, and ultimately reduces grain Cd accumulation by 39.5% in pot trials and 26.4% in field experiments.

Keywords: Seed priming, stress memory, cadmium, sustainable agriculture
Chenghao Ge, postdoctor of Nanjing University, School of the Environment. His research topics are focused on the safe production in heavy metal-contaminated farmland.