Mechanism of cadmium tolerance in Brassica juncea: an insight from comparative physiology and transcriptomics of two...

The B. juncea cv. BJ was more tolerant of Cd than the cv. JTN, and exhibited a strong tolerance to Cd via regulating antioxidant systems, sulfur metabolism, and the glutathione biosynthesis pathway. The findings offer a strategy for cultivar selection in Cd-contaminated soil phytoremediation. Cadmium (Cd) is considered one of the most poisonous metallic elements in the environment, posing a considerable threat to plant growth and productivity. Brassica juncea is anticipated to be a candidate plant for the phytoremediation of Cd contamination. In this study, different cultivars of B. juncea were used to elucidate the molecular mechanisms underlying the greater Cd tolerance of BJ (Cd tolerant) compared to JTN (Cd sensitive) by examining growth, antioxidant enzyme activity, non-enzymatic antioxidant content, and Cd transport. The results showed that BJ effectively mitigated the reduction in biomass, cell viability, and photosynthetic pigment levels, as well as the increase in malondialdehyde content and relative conductivity, in comparison with JTN. Furthermore, BJ exhibited enhanced antioxidant enzyme activities and augmented levels of non-enzymatic antioxidants. A total of 11,774 differentially expressed genes were discovered between BJ and JTN. Notably, there was a rise in the expression levels of adenosine 5'-phosphosulfate kinases (APK) genes (APK1 and APK4) and glutathione (GSH) synthetase genes (GSH1 and GSH2) linked to ATP production in the sulfur metabolic pathway and GSH synthesis pathway. Conversely, there was a decrease in the relative expression levels of ATP sulfurylase (ATPS) genes (APS1, APS2, and APS4), which regulate sulfate-activating functions and enzymatic activities associated with the GSH pathway intended to alleviate Cd stress.