Integrated comparative transcriptome and weighted gene co-expression network analysis provide valuable insights into the response mechanisms of Alisma orientale to cadmium stress.

Cadmium (Cd) pollution poses a serious challenge to the quality and safe utilization of traditional Chinese medicine plants as well as human health. In this study, seedlings of the medicinal plant species Alisma orientale were subjected to different levels of Cd stress for 7 days to investigate the effects of Cd stress on its growth, physiological response, and transcriptome profiling. The results showed that under different Cd stress levels, the growth of A. orientale displayed an inverted U-shaped dose response curve as low-dose stimulation and high-dose inhibition. Cd was mainly enriched in roots in the high concentration treatment, and Cd content reached maximum under 200-μM Cd stress. Cd stress-induced indicators including HO (14.1-228.8 % in leaves; 29.7-131.7 % in roots) and MDA (22.0-161.1 % in leaves; 30.0-201.1 % in roots) showed different degree of increase, except under 200-μM Cd stress, which had a slight decrease. Antioxidant enzyme system (SOD, POD and CAT) and nonenzymatic substances (SS, SP, total flavonoid and total polyphenols) played a key role to mitigate Cd toxic effects. Transcriptome analysis revealed 26,442 significantly differentially expressed genes, and plant-pathogen interactions and phenylpropanoid biosynthesis were identified as two key pathways. Through WGCNA joint analysis, the transcription factor genes R2R3-MYB (AoMYB12) and WRKY (AoWRKY5 and AoWRKY6) were identified as hub regulators of A. orientale in response to Cd stress. Our study provides experimental data on the effects of Cd stress on A. orientale growth and Cd accumulation in different plant parts, and investigated the transcriptomic and physio-biochemical features, advancing our understanding of the response and detoxification mechanisms of plants under Cd stress.