Abstract
The R2R3-MYB proteins comprise one of the largest families of transcription factors in plants. R2R3-MYB family members regulate plant-specific processes, such as the elaboration of specialized cell types, including xylem, guard cells, trichomes, and root hairs, and the biosynthesis of specialized branches of metabolism, including phenylpropanoid biosynthesis. As such, R2R3-MYB family members are hypothesized to contribute to the emergence of evolutionary innovations that have arisen in specific plant lineages. As a first step in determining the role played by R2R3-MYB family members in the emergence of lineage-specific innovations in the genus Populus, the entire Populus trichocarpa R2R3-MYB family was characterized. The Populus R2R3-MYB complement is much larger than that found in other angiosperms with fully sequenced genomes. Phylogenetic analyses, together with chromosome placement, showed that the expansion of the Populus R2R3-MYB family was not only attributable to whole genome duplication but also involved selective expansion of specific R2R3-MYB clades. Expansion of the Populus R2R3-MYB family prominently involved members with expression patterns that suggested a role in specific components of Populus life history, including wood formation and reproductive development. An expandable compendium of microarray-based expression data (PopGenExpress) and associated Web-based tools were developed to better enable within- and between-species comparisons of Populus R2R3-MYB gene expression. This resource, which includes intuitive graphic visualization of gene expression data across multiple tissues, organs, and treatments, is freely available to, and expandable by, scientists wishing to better understand the genome biology of Populus, an ecologically dominant and economically important forest tree genus.
Highlights
The R2R3-MYB proteins comprise one of the largest families of transcription factors in plants
The Populus R2R3-MYB family was compared with the corresponding families from the woody perennial Vitis vinifera, which is a sister taxon to Populus in Eurosids I, and the more distantly related Arabidopsis, which is a member of Eurosids II
Using the conserved N-terminal DNA-binding domain (DBD) as the defining feature, 192 genes in the P. trichocarpa genome were annotated as encoding R2R3-MYB proteins and five genes were annotated as encoding 3R-MYB proteins (Table I; Supplemental Table S1)
Summary
The R2R3-MYB proteins comprise one of the largest families of transcription factors in plants. Plant growth and development are regulated by the coordinated expression of tens of thousands of genes This is achieved through the actions of transcription factors, proteins that show sequence-specific DNA binding that activate or repress transcription in response to endogenous and exogenous stimuli (Riechmann et al, 2000). The region C terminal to the DBD is the activation domain and varies considerably between MYB proteins (Kranz et al, 1998; Jin and Martin, 1999; Stracke et al, 2001; Jiang et al, 2004). This speaks to the wide range of regulatory roles played by members of this family (Kranz et al, 1998; Jin and Martin, 1999; Meissner et al, 1999). In the Arabidopsis genome, there are five 3R-MYB genes and 126 R2R3-MYB genes (Stracke et al, 2001; Durbarry et al, 2005), while in rice (Oryza sativa), there are 84 R2R3MYB genes (Jiang et al, 2004)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
