Sunflower as a phytoremediation candidate: Multi-omics insights into mechanisms of cadmium tolerance

Cadmium (Cd) pollution severely threatens farmland ecological security and food safety. Sunflower ( Helianthus annuus L.) is a promising candidate for phytoremediation due to its high biomass and Cd accumulation capacity, but further studies are required to elucidate its mechanism of Cd tolerance. Here, we used integrated physiological, biochemical, metabolomic and transcriptomic analyses to examine the molecular responses of sunflower to Cd stress. The results show that Cd suppressed plant growth (64.97 % biomass reduction), induced oxidative stress (56.2 % increase in MDA; 133.8 % increase in SOD activity), and led to sequestration of 80 % of accumulated Cd in root cell walls. Metabolomic profiling identified 1259 differentially accumulated metabolites, highlighting the accumulation of organic acids (fumarate, citrate) and activation of glycolysis and glutathione metabolism. Transcriptomic analysis revealed 6480 differentially expressed genes, significantly enriched in phenylpropanoid biosynthesis (upregulated PAL , CCR , PRDX6 ) and glutathione metabolism (upregulated GST , GPX , G6PD ). Weighted gene co-expression network analysis identified hub genes ( SKU5 , GLPT1 ) strongly correlated with antioxidant enzyme activities. We propose a novel "three-tiered defense mechanism" comprising coordinated physical barrier formation, chemical detoxification, and energy supply networks. These findings provide critical molecular targets for breeding Cd-tolerant crops for phytoremediation applications.