Fig. 5.

Harnessing the AtPIF variants for the light-dependent regulation of gene expression in mammalian cells. a The AtPhyB PCM and AtPIF variants are connected to a VP16 trans-activating domain and an E-protein DNA-binding domain that binds to a synthetic promoter sequence. Red light promotes association of the AtPhyB:AtPIF pair and thereby activates the expression of a secreted alkaline phosphatase (SEAP) reporter gene. b SEAP expression was determined in Chinese hamster ovary cells (CHO-K1) for the diverse AtPIF6 variants and normalized to the constitutive expression of Gaussia luciferase. Black and red bars denote mean ± SEM normalized SEAP expression for n = 4 independent biological replicates under dark or red-light conditions, respectively. Cells were kept in darkness for 24 h, supplemented with PCB, and then either kept in darkness for 24 h or illuminated for 24 h with 20 µmol m⁻² s⁻¹ 660-nm light. As a negative control, the reporter construct alone was transfected. The numbers above the bars indicate the factor difference between dark and red-light conditions for a given AtPIF6 variant. c As b but for the AtPIF3 variants. d As b but for the AtPIF1 variants.