Background Cadmium (Cd) is a heavy metal with high toxicity that severely inhibits wheat growth and development. Cd easily accumulates in wheat kernels and enters the human food chain. Genetic variation in the resistance to Cd toxicity found in wheat genotypes emphasizes the complex response architecture. Understanding the Cd resistance mechanisms is crucial for combating Cd phytotoxicity and meeting the increasing daily food demand. Results Using two wheat genotypes (Cd resistant and sensitive genotypes T207 and S276, respectively) with differing root growth responses to Cd, we conducted comparative physiological and transcriptomic analyses and exogenous application tests to evaluate Cd detoxification mechanisms. S276 accumulated more H2O2, O2−, and MDA than T207 under Cd toxicity. Catalase activity and levels of ascorbic acid (AsA) and glutathione (GSH) were greater, whereas superoxide dismutase (SOD) and peroxidase (POD) activities were lower in T207 than in S276. Transcriptomic analysis showed that the expression of RBOHA, RBOHC, and RBOHE was significantly increased under Cd toxicity, and two-thirds (22 genes) of the differentially expressed RBOH genes had higher expression levels in S276 than inT207. Cd toxicity reshaped the transcriptional profiling of the genes involving the AsA-GSH cycle, and a larger proportion (74.25%) of the corresponding differentially expressed genes showed higher expression in T207 than S276. The combined exogenous application of AsA and GSH alleviated Cd toxicity by scavenging excess ROS and coordinately promoting root length and branching, especially in S276. Conclusions The results indicated that the ROS homeostasis plays a key role in differential Cd resistance in wheat genotypes, and the AsA-GSH cycle fundamentally and vigorously influences wheat defense against Cd toxicity, providing insight into the physiological and transcriptional mechanisms underlying Cd detoxification.

Background: Understanding the cadmium (Cd) resistance mechanism is crucial for combating the phytotoxicity of Cd and meeting the increasing food demand daily. A classic symptom of Cd toxicity is root growth inhibition. Results: Using two wheat genotypes (Cd tolerant genotype T207 and Cd sensitive genotype S276) with differing root growths in response to Cd, we conducted comparative physiological and transcriptomic analyses and exogenous application tests to interpret Cd detoxification mechanisms. S276 accumulated more H2O2, O2-, and malonaldehyde than T207. Catalase activity and levels of ascorbic acid (AsA) and glutathione (GSH) were higher, whereas superoxide dismutase and peroxidase activities were lower in T207 than in S276. Transcriptome analysis showed that the expression of RBOHA, RBOHC, and RBOHE significantly increased, whereas that of RBOHB markedly decreased by Cd treatment. The transcriptional levels of 22 genes encoding RBOH were higher, and that of 11 genes were lower in T207 than in S276. The transcription of genes involved in the AsA-GSH cycle was profoundly reshaped by Cd treatment; 124 genes were higher and 43 genes were lower in T207 than in S276. Exogenous combined application of AsA and GSH alleviated Cd toxicity by scavenging excess ROS and coordinately modulating root length and branching, especially in S276.Conclusions: These results indicate that the AsA-GSH cycle fundamentally and vigorously influences plant defense against Cd toxicity, which provides valuable information for further clarification of the mechanisms underlying Cd detoxification.