Bioaccumulation and detoxification mechanisms for lead uptake identified in Cosmos sulphureus Cav. seedlings

Lead (Pb) stress disrupts plant growth and cellular homeostasis; however, the underlying multi-omics molecular network and Pb immobilization mechanisms in Cosmos sulphureus Cav. remain to be fully clarified. Here, Pb toxicity significantly reduced leaf area and biomass, while root morphology exhibited a dose-dependent biphasic response. C. sulphureus predominantly retains Pb in roots, supported by boosted ROS defenses (elevated SOD, CAT, MDA) and osmotic acclimation. We identified 400 μM as the physiological tolerance threshold, characterized by high metal retention and low systemic translocation. Multi-omics integration revealed a coordinated defense framework: pectin and HC1 serve as primary binding sites, where uronic acid enrichment, pectin remodeling to low-methylesterified pectin (LMP) exposing free carboxyl groups (- COOH), and HC1 acetylation drive cell wall Pb immobilization. Concurrently, proline accumulation-marked by co-upregulation of P5CS, P5CR, and aat2 with L-proline-facilitates cellular homeostasis. Overall, coordinated pectin demethylation, HC1 modification, and proline metabolic reconfigurations drive root-based Pb phytostabilization in C. sulphureus, offering baseline theoretical insights for phytoremediation.