Unveiling Si's shield: A holistic examination of Cd stress alleviation in maize through physiological and transcriptomic insights

Cadmium (Cd), present in agricultural soil, poses a substantial threat to public health through the food chain, adversely affecting food crops and yield. This study examined the role of silicon (Si) in alleviating Cd stress in maize (Zea mays L.). Germinated uniform seedlings were transplanted into 20 L pots filled with a lowconcentration nutrient solution. At the three fully expanded leaves stage (21 days after transplanting), plants were treated with Si (1000 mu\M as K2SO3) and Cd (10 mu M as CdCl2). Plants were assessed 0, 1, and 28 days after treatments. The results demonstrate that Si application leads to a reduction in Cd concentration and content in maize shoot tissue. Additionally, Si treatment positively influences the activity of antioxidant enzymes (peroxidase, superoxidase dismutase, catalase) and plant hormones (abscisic acid, gibberellic acid, salicylic acid) in maize leaves. Furthermore, Si application enhances plant growth, increases levels of antioxidant substances, improves gas exchange parameters, boosts chlorophyll content, and enhances fluorescence. Weighted gene coexpression network analysis (WGCNA) and identification of transcription factors (TFs) and structural genes among differentially expressed genes (DEGs) reveal physiological correlations and enriched signaling pathways, particularly those related to metabolism and biosynthesis. Si actively modulates the formation of metabolites such as arginine and proline, starch and sucrose, as well as biosynthetic pathways for secondary metabolites like benzoxazinoid and carotenoid. Additionally, Si exerts regulatory influence over pathways such as the MAPK signaling pathway and plant hormone signal transduction in plants subjected to Cd stress. These findings unveil the molecular mechanisms underpinning the alleviation of Cd-induced stress in maize leaves due to Si application. Consequently, Si application not only mitigates Cd stress in maize but also reduces the risk of Cd entering the food chain.