Phylogeny of R2R3 MYB transcription factors involved in PA and flavonoid biosynthesis. Functionally characterized MYB factors, uncharacterized MYBs with enhanced expression in MYB134-overexpressing transgenic poplars, and other poplar and Arabidopsis MYBs grouping with the characterized MYBs are shown. The phylogeny was constructed using the maximum likelihood method, and bootstrap values were calculated from 1,000 phylogenetic constructions. Arrows mark positions of the two MYBs studied here, and asterisks indicate poplar MYB genes showing enhanced expression in MYB134-overexpressing transgenics. Accession numbers are listed in “Materials and Methods.”