Physiological, transcriptomic and metabolomic analyses reveal that exogenous arginine alleviate the response of Sorghum bicolor L. to cadmium stress

Cadmium (Cd) contamination presents a significant risk to crop development and yield. As a non-redox heavy metal, Cd triggers reactive oxygen species generation, causing cell death in plants. Arginine (Arg), a beneficial amino acid, has shown promise in alleviating Cd stress, but the underlying molecular mechanisms remain inadequately understood. This study sought to explore how 1.0 mM of exogenous Arg alleviates Cd toxicity in sweet sorghum seedlings using physiological profiling, RNA sequencing, and non-targeted metabolomics. Exogenous Arg application boosted antioxidant enzyme activity, mitigated Cd toxicity, and promoted growth. It also increased Cd accumulation in roots by 167.62 % through up-regulating genes involved in the production of metabolites like glutathione, polyamines, pectin, and lignin, which strengthened cell walls and facilitated Cd chelation. Additionally, Arg enhanced the function of transporters such as Yellow Stripe-Like (YSL), Heavy-metal-associated isoprenylated plant proteins (HIPP), and Heavy Metal ATPase (HMA), maintaining ion homeostasis. The metabolomic analysis uncovered that Arg increased amino acid and organic acid accumulation, thereby enhancing stress resilience by influencing the Arg biosynthesis pathway and cysteine-methionine metabolism. This study provides the first comprehensive exploration of the mechanisms by which exogenous Arg mitigates Cd stress in plants, offering a novel insight into the molecular mechanisms behind Arg-mediated Cd tolerance, offering a foundation for breeding Cd-tolerant plants and advancing phytoremediation strategies.