Integrative Physiological and Transcriptome Analysis Reveals the Mechanism of Cd Tolerance in Sinapis alba

Recently, pollution caused by the heavy metal Cd has seriously affected the environment and agricultural crops. While is known for its edible and medicinal value, its tolerance to Cd and molecular response mechanism remain unknown. This study aimed to analyze the tolerance of to Cd and investigate its molecular response mechanism through transcriptomic and physiological indicators. To achieve this, seedlings were treated with different concentrations of CdCl (0.25 mmol/L, 0.5 mmol/L, and 1.0 mmol/L) for three days. Based on seedling performance, exhibited some tolerance to a low concentration of Cd stress (0.25 mmol/L CdCl ) and a strong Cd accumulation ability in its roots. The activities and contents of several antioxidant enzymes generally exhibited an increase under the treatment of 0.25 mmol/L CdCl but decreased under the treatment of higher CdCl concentrations. In particular, the proline (Pro) content was extremely elevated under the 0.25 and 0.5 mmol/L CdCl treatments but sharply declined under the 1.0 mmol/L CdCl treatment, suggesting that Pro is involved in the tolerance of to low concentration of Cd stress. In addition, RNA sequencing was utilized to analyze the gene expression profiles of exposed to Cd (under the treatment of 0.25 mmol/L CdCl ). The results indicate that roots were more susceptible to disturbance from Cd stress, as evidenced by the detection of 542 differentially expressed genes (DEGs) in roots compared to only 37 DEGs in leaves. GO and KEGG analyses found that the DEGs induced by Cd stress were primarily enriched in metabolic pathways, plant hormone signal transduction, and the biosynthesis of secondary metabolites. The key pathway hub genes were mainly associated with intracellular ion transport and cell wall synthesis. These findings suggest that is tolerant to a degree of Cd stress, but is also susceptible to the toxic effects of Cd. Furthermore, these results provide a theoretical basis for understanding Cd tolerance in .