MAN3 gene regulates cadmium tolerance through the glutathione‐dependent pathway in Arabidopsis thaliana

Summary Pollution of soil by the heavy metal cadmium (Cd) is a global environmental problem. The glutathione ( GSH )‐dependent phytochelatin ( PC ) synthesis pathway is one of the most important mechanisms contributing to Cd accumulation and tolerance. However, the regulation of this pathway is poorly understood. Here, we identified an Arabidopsis thaliana cadmium‐tolerant dominant mutant xcd1‐D ( XVE system‐induced cadmium‐tolerance 1 ) and cloned XCD 1 gene (previously called MAN 3 ), which encodes an endo‐β‐mannanase. Overexpression of MAN 3 led to enhanced Cd accumulation and tolerance, whereas loss‐of‐function of MAN 3 resulted in decreased Cd accumulation and tolerance. In the presence of estradiol, enhanced Cd accumulation and tolerance in xcd1‐D was associated with GSH ‐dependent, Cd‐activated synthesis of PC s, which was correlated with coordinated activation of gene expression. Cd stress‐induced expression of MAN 3 and the consequently increased mannanase activity, led to increased mannose content in cell walls. Moreover, mannose treatment not only rescued the Cd‐sensitive phenotype of the xcd1‐2 mutant, but also improved the Cd tolerance of wild‐type plants. Significantly, this mannose‐mediated Cd accumulation and tolerance is dependent on GSH ‐dependent PC concentrations via coordinated control of expression of genes involved in PC synthesis. Our results suggest that MAN 3 regulates the GSH ‐dependent PC synthesis pathway that contributes to Cd accumulation and tolerance in A. thaliana by coordinated control of gene expression.