The prey vector pGADT7 expressing PPK or PPKC fused to the GAL4 activation domain and the Bait vector pBridge expressing CRY2 fused to the GAL4 DNA binding domain were used. The pairs of plasmids were co-transformed into yeast strain AH109. Colonies were selected on plates (SD-LW). After culture in SD-LW medium for 16 h (Dark), transformants were subcultured into fresh SD-LW medium and kept in dark or irradiated with blue light (30 mol m-2 s-1). β-galactosidase activity was measured using chlorophenol red-β-D-galactopyranoside as substrate and Miller Units were calculated according to the Clontech Yeast Protocols Handbook.