Integrated transcriptomic and metabolomic analysis reveals the molecular mechanisms of cadmium stress response in rapeseed (Brassica napus L.): Insights into glutathione and sulfur metabolism pathways

Cadmium (Cd) is one of the heavy metal pollutants in soil. Cd stress affects the growth and development of rapeseed and significantly reduces its yield and quality. Here, we conducted a comprehensive analysis combining transcriptomic and metabolomic analyses to explore the molecular mechanisms of rapeseed response to Cd stress. The rapeseed seedlings were treated with 5 concentrations (0, 100, 200,300, and 400 μM) of Cd. Seedlings exposed to Cd (0–400 μM) exhibited dose-dependent growth inhibition alongside increased proline accumulation and elevated superoxide dismutase (SOD) and peroxidase (POD) activities. Integrated analysis revealed that differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) in roots were predominantly enriched in glutathione (GSH) metabolism, glucosinolate (GSL) biosynthesis, ABC transporters, and phenylpropanoid biosynthesis pathways. In shoots, DEGs and DAMs were primarily associated with MAPK signaling, GSH metabolism, and photosynthesis. Further analysis indicated that Cd stress redirected sulfur flux toward GSH metabolism at the expense of GSL biosynthesis. Moreover, genetic transformation experiments demonstrated that overexpression of BnaMYB28 enhanced Cd tolerance by promoting GSH and sulfur metabolism. Our findings elucidate the molecular response mechanism of rapeseed to Cd stress and provide a foundation for improving Cd tolerance.