Figure 4.

Evaluation of the Zn and Cd transport activity of the OsZIP5 and OsZIP9 proteins in yeast mutants and rice protoplasts. A and D, pYES2-OsZIP5, pYES2-OsZIP9, and the empty vector pYES2 were separately introduced into the Zn-sensitive strain Δzrc1 (A) and the Cd-sensitive strain Δycf-135c (D). Yeast strains were cultured on SC-Ura plates containing different concentrations of Zn (A) and Cd (D) at 28°C for 2 to 4 d. B and E, Growth rates of yeast cells. Yeast mutant strains transformed with the empty vector pYES2, pYES2-OsZIP5, or pYES2-OsZIP9 in 3 mm Zn (B) or 30 μm Cd (E) in SC-Ura medium. OD600 values of pYES2-OsZIP5 and pYES2-OsZIP9 strains were significantly different compared with the empty vector strain. C and F, Zn (C) and Cd (F) levels in yeast cells. Yeast mutant strains transformed with the empty vector pYES2, pYES2-OsZIP5, or pYES2-OsZIP9 were treated with 3 mm Zn or 30 μm Cd for 40 to 50 h. G and H, Zn (G) and Cd (H) uptake in rice protoplasts. Rice protoplasts were cultured in W5 buffer with⁶⁷Zn (G) and Cd (H) for 18 h. Data for ∆⁶⁷Zn and ∆Cd quantification were calculated from the net increases in ⁶⁷Zn and Cd (i.e. the total ⁶⁷Zn amount minus the natural abundance of ⁶⁷Zn). Values represent means ± sd of biological replicates (n ≥ 3). Statistical comparison was performed by Tukey’s HSD mean-separation test (*P < 0.05 and **P < 0.01). WT, Wild type.