FIGURE 7.

Cd analysis in OsCCX2-expressing yeast cells and in cell sap of the ccx2 plant. (A) Cadmium tolerance of yeast cells expressing OsCCX2. Yeast liquid cultures were grown and adjusted to an optical density of 0.5 at OD600, and 5 μl aliquots of serial dilutions (10^-1,10^-2, 10^-3, and 10^-4) were plated onto SD-Ura medium without CdCl₂ (the upper two rows), or containing certain concentrations of CdCl₂ (10 μM for the middle two rows and 20 μM for the bottom two rows). The plates were further incubated at 30°C for 3 days (left panels) and 4 days (right panels), respectively. The ycf1 mutants were transformed pYES2 empty vector or pYES2-OsCCX2. Data are representative values of three independent experiments. (B) Cd content of transformants grown on CdCl₂-containing media. The pYES2-OsCCX2 and pYES2 empty vectors were transformed into wild type yeast BY4741, respectively. The transformants were grown on SD liquid cultures for 24 h (containing 1, 2, 5, and 10 μM CdCl₂, respectively), and the Cd content was determined. Data are average values of three independent experiments and are presented as mean ± SD. (C,D) Two-week-old seedlings were transplanted to 5 μM Cd-containing hydroponic solution, and the shoots and roots were collected at 1, 2, 3, 4, 5, 6, and 7 days. The shoot and the root were homogenized and subcellular fractions were separated by using differential centrifugation techniques. Data are average values of three independent experiments and are presented as mean ±SD.