Interaction of ABA receptor components analyzed by BiFC. Pairs of PYR/PYL5-YFP^C/PP2C4-YFP^N, PYR/PYL5-YFP^C/PYR/PYL5-YFP^N, and PP2C4-YFP^C/PKABA1/SNRK2.1-YFP^N were transformed into Arabidopsis protoplasts. Fluorescence images were taken 1 d after transformation. The pictures are YFP, bright field, autofluorescence (auto), and merged images.