Overexpression of a Functional PCS1 Homolog Increases Cadmium Tolerance and Phytochelatins Synthesis in Arabidopsis.

Phytochelatins (PCs) catalyzed by phytochelatin synthases (PCS) are important for the detoxification of metals in plants and other living organisms. In this study, we isolated a gene () from and investigated its role in regulating cadmium (Cd) tolerance. Expression of was induced in roots of under Cd stress. Analysis of subcellular localization showed that VsPCS1 was localized in the cytoplasm of mesophyll protoplasts of . Overexpression of (, in wild-type background) in could complement the defects of Cd tolerance of -deficent mutant (). Compared with mutants, (in -deficent mutant background) transgenic plants significantly lowered Cd-fluorescence intensity in mesophyll cytoplasm, accompanied with enhanced Cd-fluorescence intensity in the vacuoles, demonstrating that the increased Cd tolerance may be attributed to the increased PC-based sequestration of Cd into the vacuole. Furthermore, overexpressing could enhance the Cd tolerance in , but have no effect on Cd accumulation and distribution, showing the same level of Cd-fluorescence intensity between and wild-type (WT) plants. Further analysis indicated this increased tolerance in was possibly due to the increased PCs-chelated Cd in cytosol. Taken together, a functional PCS1 homolog from was identified, which hold a strong catalyzed property for the synthesis of high-order PCs that retained Cd in the cytosol rather the vacuole. These findings enrich the original model of Cd detoxification mediated by PCS in higher plants.