A poplar R2R3-MYB transcription factor, PtrMYB152, is involved in regulation of lignin biosynthesis during secondary cell wall formation

Wood is the most abundant biomass in perennial woody plants. Extensive studies have shown that R2R3-MYB transcription factors are involved in regulation of lignin biosynthesis during secondary cell wall formation in many plant species, such as Arabidopsis, rice, maize and poplar. In this study, a MYB transcription factor, named PtrMYB152, was isolated from Populus trichocarpa and encoded a protein of 321 amino acids that contained a conserved R2R3-MYB domain. Phylogenetic analysis revealed that PtrMYB152 shares high sequence homology with other known plant MYBs associated with secondary wall formation. PtrMYB152 is specifically expressed in secondary wall-forming cells in poplar. Histochemical localizations of GUS expression in the transgenic Arabidopsis plants showed that PtrMYB152 is predominantly expressed in vascular tissues. Overexpression of PtrMYB152 resulted in specific activation of lignin biosynthetic genes, and caused ectopic deposition of lignin in stem and petiole of transgenic plants. These data indicated that PtrMYB152 is a specific transcriptional activator of lignin biosynthesis during wood formation of poplar.