Additional file 1: Table S1. of Kinetic Analysis of Zinc/Cadmium Reciprocal Competitions Suggests a Possible Zn-Insensitive Pathway for Root-to-Shoot Cadmium Translocation in Rice

Fractioning of Zn ions retained in root. Table S2 Fractioning of Cd ions retained in root. Table S3 Zn ions retained in the root in complexes with thiols. Table S4 Cd ions retained in the root in complexes with thiols. Figure S1 Relationship between Zn and Cd ions loaded in the xylem sap and Zn and Cd concentration in shoots. Figure S2 Fractioning of Zn and Cd ions in the buffer extract. Figure S3 Zn‐ and Cd‐binding complexes resolved by gel filtration chromatography. Figure S4 Autoradiography and time‐course analysis of Cd accumulation in the shoot base. Figure S5 Another set of time‐course analysis of Cd systemic movement. (PDF 1.39 mb

Kinetic Analysis of Zinc/Cadmium Reciprocal Competitions Suggests a Possible Zn-Insensitive Pathway for Root-to-Shoot Cadmium Translocation in Rice

Cadmium (Cd) and zinc (Zn) translocation in rice was studied by analyzing a complete set of competition experiments in which plants were exposed to increasing Zn external concentrations (0.1, 1, and 10 µM), in the absence or presence of 0.1 µM Cd2+, or to different Cd concentrations (0, 0.01, 0.1, and 1 µM) in the presence of 1 µM Zn2+. Results revealed the lack of a full reciprocity when considering the effect of Cd on Zn accumulation, and vice versa, since the accumulation of Zn in the shoots was progressively inhibited by Cd increases, whereas that of Cd was only partially impaired by Zn. Such behaviors probably involved the mechanisms of Cd-xylem loading, as suggested by: i) the analysis of Zn and Cd content in the xylem sap performed in relation to the concentration of the two metals in the mobile fractions of the roots; ii) the analysis of the systemic movement of 107Cd in short term PETIS experiments. From these results we suggest that at least two pathways may mediate root-to-shoot Cd translocation in rice. The former could involve OsHMA2 as Zn2+/Cd2+ xylem loader, whereas the latter appears to involve a Zn-independent system that still needs to be identified