Fig. 6. MYB3R1 and MYB3R4 act as transcriptional activators. (A) Activation of KN gene promoter by MYB3R1 and MYB3R4. KN::LUC reporter plasmid and 35S::MYB3R1 or 35S::MYB3R4 expression plasmid were co-transfected into tobacco BY-2 protoplasts, either with or without 35S::CYCB1. (B) MSA elements are required for MYB3R4-induced activation of the KN promoter. The KNMSA::LUC construct contains the KN promoter in which all three MSA elements are mutated. KN::LUC and KNMSA::LUC were transfected into tobacco BY-2 protoplasts together with 35S::MYB3R4 expression plasmids, either with or without 35S::CYCB1. (C) Effects of MYB3R4 on the activity of G2/M phase-specific promoters. Each promoter was fused to LUC and transfected into tobacco BY-2 protoplasts together with 35S::MYB3R4 expression plasmids, either with or without 35S::CYCB1. All LUC activities in A, B and C are normalized relative to the control transfection without expression plasmid. Bars represent mean values in each of five independent transfections; error bars represent s.d.