Phytochelatin synthesis and cadmium localization in wild type of Arabidopsis thaliana

Although Arabidopsis thaliana is known as a model plant, in molecular studies, as well as heavy metal tolerance of higher plants, there have been no detailed studies of its cadmium accumulation, tolerance and cellular distribution in a wild type of this species. In hydroponic experiments the wild type of A. thaliana (L.) Heynh cv. Columbia plants grew at cadmium concentrations varying from 5 to 100 muM with phytotoxicity symptoms depending on the concentration and time of application. The concentration of cadmium in roots and shoots increased from 0.28 and 0.08 mg g(-1) d.wt at 5 muM Cd treatment after 7 days to 0.82 and 0.85 mg g(-1) d.wt at 100 muM Cd treatment after 14 days, respectively. Most of the cadmium (69-88% of its total pool) was found in shoot. Cd application induced the biosynthesis of phytochelatins (PCs) in root and shoot tissues. Studies with buthionine sulfoximine [BSO, specific inhibitor of glutathione (GSH) synthesis] supported the presence of Cd-phytochelatin complexes and their role in Cd detoxification and tolerance in wild type of A. thaliana. Cellular distribution of cadmium was examined using energy-dispersive X-ray micro-analysis. Particularly interesting was the observation of cadmium localized in the root pericycle.