Figure 5 MYB52 regulates the promoter activity of  PHT1;1.  A, A schematic illustration of constructs used for the analysis of  PHT1;1  promoter activity in a dual-luciferase assay. B,  PHT1;1  promoter activity was defined as the ratio of LUC:REN (firefly:renilla). Transformation with the empty vector served as a negative control. Data are presented as mean ±  se  ( n  = 4 biologically independent samples). The significance of differences was determined by two-sided Student’s  t  test (** P  < 0.01).