Sulfur mediates cadmium accumulation and detoxification through distinct pathways in two Nicotiana species

Cadmium (Cd) is a heavy metal pollutant that impedes plant growth. Sulfur (S), a nutrient, possesses the ability to detoxify Cd. Nevertheless, the dose effect of S on Cd detoxification and the mechanism by which S modulates Cd accumulation and detoxification, remain insufficiently understood. Here, two Nicotiana species with distinct Cd accumulation strategies were hydroponically cultivated under varying S:Cd molar ratios (250:1, 500:1, 750:1, 1000:1). This study aimed to assess the effects of different S doses on Cd accumulation and detoxification and to clarify the underlying mechanisms from multiple perspectives. Results identified 500:1 as the optimal S:Cd ratio, beyond which detoxification diminished, reflecting a hormetic response. Integrated physiological, biochemical, transcriptomic, and metabolomic analyses revealed species-specific pathways of S-mediated detoxification between two Nicotiana species. Specifically, the S-mediated Cd translocation factor from roots to leaves in N. tabacum increased from 1.22 to 2.70, whereas it decreased from 0.25 to 0.20 in N. rustica. N. tabacum prioritizes shoot-based Cd detoxification via glutathione mobilization (62.96 % increase), transporter activation (NRAMP/HMA/ZIP), and enhanced trichome secretion (1.12-fold glandular trichome density). Conversely, in N. rustica, S redirected metabolism towards phytochelatins-dominated thiols (1.22-fold), enhancing Cd chelation detoxification, along with lignin fortification (3 % increase in cell wall Cd) and vacuolar sequestration (ABC/CAX) in roots. These findings demonstrate that S mediates divergent detoxification strategies across species, offering potentially valuable information for developing targeted strategies to enhance crop Cd remediation, either via shoot-driven phytoextraction or root-based immobilization for food safety.