Controls of BiFC assays in C. roseus cells. Cells were co-transformed using a combination of plasmids as indicated: (A-C) the split of nuclear transcription factor bZIP as a positive control. An additional co-transformation with the CFP nuclear marker (B) confirms the co-localization of the two fluorescence signals (C). (D-O) YFPN-HPt9/-RR13 or YFPC-HPt2/-RR16 with the split bZIP as a negative control. For each combination, an additional co-transformation with the CFP nuclear marker was performed (E, H, K, N). The morphology was observed by differential interference contrast (DIC) microscopy (C, F, I, L, O). Scale bar = 10 μm.