The role and transcriptomic mechanism of cell wall in the mutual antagonized effects between selenium nanoparticles and cadmium in wheat

Selenium nanoparticles (SeNPs) has been reported as a beneficial role in alleviating cadmium (Cd) toxicity in plant. However, underlying molecular mechanisms about SeNPs reducing Cd accumulation and alleviating Cd toxicity in wheat are not well understood. A hydroponic culture was performed to evaluate Cd and Se accumulation, cell wall components, oxidative stress and antioxidative system, and transcriptomic response of wheat seedlings after SeNPs addition under Cd stress. Results showed that SeNPs application notably reduced Cd concentration in root and in shoot by 56.9% and 37.3%, respectively. Additionally, SeNPs prompted Cd distribution in root cell wall by 54.7%, and increased lignin, pectin and hemicellulose contents by regulating cell wall biosynthesis and metabolism–related genes. Further, SeNPs alleviated oxidative stress caused by Cd in wheat through signal transduction pathways. We also observed that Cd addition reduced Se accumulation by downregulating the expression level of aquaporin 7. These results indicated that SeNPs alleviated Cd toxicity and reduced Cd accumulation in wheat, which were associated with the synergetic regulation of cell wall biosynthesis pathway, uptake transporters, and antioxidative system via signaling pathways. This manuscript clarifies that selenium nanoparticles (SeNPs) could effectively reduce Cd accumulation in wheat by prompting Cd binding in root cell wall. Besides, SeNPs notably increased root cell wall components and changed cell wall structure. Additionally, SeNPs alleviated Cd toxicity by inhibiting oxidative stress and regulating AsA–GSH cycle. The manuscript identified the key differentially expressed genes and transcriptional pathways affected by SeNPs in wheat under Cd stress. On the other hand, the mechanism of Cd reducing Se accumulation was also clarified. In all, the work revealed molecular mechanism in mutual antagonized effects between SeNPs and Cd in wheat.