Differences in root-to-shoot Cd and Zn translocation and by HMA3 and 4 could influence chlorophyll and anthocyanin content in Arabidopsis Ws and Col-0 ecotypes under excess metals

Judging from the ecotypic variability in Arabidopsis thaliana L., Columbia-0 (Col-0) appears to be less tolerant to cadmium (Cd) than the Wassilewskija (Ws) ecotype that possesses the full-length Heavy Metal ATPase3 (HMA3) cDNA. In this study, the Ws and Col-0 were tested to determine toxic metal response between Ws and Col-0 due to AtHMA3 point mutation and/or other factors. The growth inhibition of Col-0 mediated by Cd and zinc (Zn) was more serious than the inhibition of Ws, while no significant difference was evident by lead (Pb) and cobalt (Co). In the presence of Cd stress, chlorosis in leaves of Col-0 was more serious than the Ws ecotype. When grown under hydroponic culture containing 500?µM Zn, leaves of Col-0 showed a remarkable increase in the anthocyanin content in a dose-dependent manner and the expression of genes encoding enzymes involved in anthocyanin synthesis in the leaves. The rate of root-to-shoot translocation of Cd and Zn in the Col-0 was 2 times higher when compared with the Ws, whereas roots of the Col-0 accumulated 2 times lower Cd and Zn concentrations than those of the Ws. Real-time polymerase chain reaction (PCR) analyses indicated that not only the alteration of the expression of HMA3 but also of the HMA4 was responsible for the root-to-shoot translocation of toxic metals. The results demonstrate that the Col-0 is readily translocating Cd and Zn to the aerial parts but not the Ws, thereby induce the alteration of phenotype in leaf color.