PIF4 interacts with TCP4 and regulates KRP1 expression. A and B, Luciferase transactivation assay showing binding of PIF4 (A) and TCP4 (B) to the KRP1 promoter in N. benthamiana leaves. C, Dual-luciferase assay in N. benthamiana leaves co-infiltrated with different transcription factors. LUC/REN ratio represents the relative activity of the KRP1 promoter, where REN was used as an internal control. Values represent mean ± se (n = 5) E.V., empty vector. Stars indicate Student’s t test P < 0.05. D, Split Luciferase assay showing protein–protein interaction between PIF4 (cloned with cLUC) and TCP4 (cloned with nLUC). E, BiFC assays in N. benthamiana showing an interaction between PIF4 and TCP4. NLS-RFP is used as a nuclear marker. Scale = 30 µm. F, Yeast two-hybrid assays showing an interaction between PIF4Δ53 and TCP4. The DBD was fused to truncated PIF4 named as PIF4Δ53, and the activation domain was fused to TCP4.