Fig. 1. Molecular characterization of MYB3R1 and MYB3R4. (A) Phylogenetic relationship of R1R2R3-Myb proteins in plants. The phylogenetic tree was constructed based on the amino acid sequence similarities in the Myb domains of R1R2R3-Myb proteins from tobacco (NtmybA1, NtmybA2 and NtmybB), Arabidopsis (MYB3R1-MYB3R5) and rice (Os01g12860, Os12g13570, Os01g62410 and Os05g38460). (B) Protein structure of MYB3R1 and MYB3R4. The Myb domain is located in the N-terminus and contains tandemly repeated sequences that are designated R1, R2, and R3 (black boxes). Two separate regions in the C-terminal half show sequence similarity to their homologs in tobacco and rice (hatched boxes). (C) Position of T-DNA insertions in MYB3R1 and MYB3R4. Boxes and lines represent exons and introns, respectively. Arrows above the boxes indicate positions of T-DNA insertions. Black and white boxes correspond to coding and non-coding regions, respectively. Arrowheads indicate the positions of primers used for quantitative RT-PCR. (D) Transcript levels of MYB3R1 and MYB3R4 in wild-type and T-DNA insertion mutants. Levels of each transcript were determined by real-time quantitative RT-PCR using the primer pairs shown in C.