Overexpression of TgMYB2 from the teak MYB gene family impacts biomass accumulation and secondary cell wall in tobacco plants.

Teak is a tropical forest tree of great commercial importance. This hardwood species has been considered the best decorative wood in the world with extraordinary qualities of color, density and durability. Despite its commercial importance, molecular mechanisms regulating wood formation in teak are still obscure. In plants, the MYB transcription factors (TFs) are the master switches in the regulation of secondary cell wall biosynthesis. Previous transcriptome analyses of the secondary xylem of teak trees have identified high expression of MYB in young tree stems. In the present work, the full-length coding sequence of the TgMYB2 gene was isolated from teak young stems, characterized, cloned and constitutively overexpressed in tobacco plants. Phylogenetic relationships and molecular analyses recognized TgMYB2 as a 3R-MYB protein, which contains conserved motifs identified as R1-R2-R3 MYB repeats. In transgenic tobacco plants, the overexpressed TgMYB2 protein was localized exclusively in the cell nucleus, as expected for a transcription factor. The overexpressed TgMYB2 significantly modified secondary plant growth and improved biomass. Furthermore, we provide evidence that TgMYB2 plays an important role in the coordinated regulation of cellulose, hemicellulose, and lignin biosynthetic pathways.