Abstract
Cadmium (Cd) is a highly toxic heavy metal with strong bioaccumulation potential in living organisms. Its phytotoxic effects mainly arise from disruption of cellular redox homeostasis, displacement of essential mineral elements, and impairment of normal organ function. Understanding the mechanisms underlying Cd-induced injury and plant stress responses is critical for developing low-Cd-accumulating and Cd-tolerant crop varieties. During cultivar screening, a maize variety (H03) with high Cd accumulation was identified, exhibiting 9.3-fold higher Cd accumulation in its aerial part compared to a normal Cd-accumulating variety (L9819). We then analyzed the physiological traits of this variety as well as changes in gene expression and metabolite accumulation. Under Cd stress, H03 displayed adaptive morphological adjustments, particularly in root system architecture, and increased catalase (CAT) activity in roots, stems and leaves by 1.2- to 5.8-fold. Transcriptomic analysis identified numerous differentially expressed genes (DEGs) exhibiting tissue-specific response patterns, including transcription factors such as Ethylene Response Factors (ERFs), basic Helix-Loop-Helix (bHLH), and MYB-related proteins. Differentially accumulated metabolites (DAMs) revealed the accumulation of key stress-responsive metabolites, notably phenylalanine—the precursor of the phenylpropanoid pathway—and its downstream derivatives. Integrated transcriptomic and metabolomic analyses suggest that Cd tolerance in H03 is primarily mediated through AP2-regulated activation of the phenylpropanoid pathway, facilitating metabolite-based detoxification. Overall, these findings elucidate the molecular network underlying Cd detoxification in H03 and provide a theoretical foundation for its utilization in crop improvement and phytoremediation strategies.