Functional complementation of S. cerevisiae ctr1Δctr3Δ mutant (MPY17) by expression of rice COPTs. Yeast ScCtr1 was used as positive control. Empty vector (V) was used as negative control. Transformants were grown in SC-His or SC-His-Ura medium to exponential phase and then spotted onto ethanol/glycerol (YPEG)-selective media supplemented with 5 to 50 μM CuSO4 or without supplementation of CuSO4 (0). (a) Expression of COPTs alone. (b) Coexpression of COPTs. The p413 and p416 are yeast expression vectors.