Fig. 1

Transactivation analysis of the CSE promoter by secondary wall-associated transcription factors in tobacco protoplasts. a Putative SNBE and SMRE sequences identified from the promoter region 2-kb upstream of the start codon of CSE. The numbers on the left indicate the position relative to the translational start site, while symbols on the right indicate whether the sequence was identified in the forward (+) or reverse (−) strands of the DNA. The consensus nucleotides in the SNBE and SMRE sequences are shaded in gray. b Schematic representation of the effector and reporter constructs. The effector construct consists of the constitutive CaMV 35S promoter driving the expression of secondary wall-associated (SCW) transcription factors, while the reporter construct consists of the CSE promoter driving the expression of firefly luciferase reporter gene (fLUC). c Transactivation analysis showing that only second-level MYB master switches (MYB46 and MYB83) and lignin-specific activators (MYB63 and MYB85) effectively activate the expression of the proCSE-driven fLUC reporter gene. Values are fold-changes normalized to protoplasts co-transfected with the reporter constructs and a CaMV 35S::GUS control plasmid. Error bars indicate the standard deviation and significance was determined by Student’s t test (***P < 0.001; n = 8)