Analysis of activation of the chs _H1 promoter (A) and the whole chs _H1 gene (B). The combinatorial transient expression assay by analysis of GUS activity was performed to analyze promoter activation (A); the relative levels of chs_H1 mRNA were determined by RT qPCR and normalized against the elongation factor 1 housekeeping gene to analyze the activation of chs_H1 gene by the TFs (B). Infiltrated A. tumefaciens strains in panel A: C-control, infiltration of A. tumefaciens LBA 4404 without plant vector; M2, HlMyb2; s-M3; s-HlMyb3; +W1, combinations with HlWDR1; +B2, combinations with HlbHLH2; +B2W1, combinations with HlbHLH2 and HlWDR1, 35S:GUS, ß-glucuronidase driven from 35S promoter of CaMV. The samples in panel B: 1, control infiltration of LBA 4404; 2, chs_H1 gene; 3, chs_H1 gene plus TF combination HlMyb2/HlbHLH2/HlWDR1; 4, chs_H1 gene plus TFs in combination s-HlMyb3/HlbHLH2/HlWDR1. Bars represent the confidence intervals at level α = 0.05.