Comparative Physiological and Transcriptomic Analyses Reveal Ascorbate and Glutathione Coregulation of Cadmium Toxicity Resistance in Wheat Genotypes

Abstract

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.