Figure 3.

Phylogenetic trees of Poplar, grape, Medicago and soybean BTB protein families. BTB domains in the BTB family of four organisms identified by InterproScan were used to generate a midpoint-rooted NJ (neighbor joining) tree. The trees were created by Mega 4.0 with 1000 bootstrap replicates. Solid boxes on the nodes of the trees present higher bootstrap support (≥ 90%), and hollow ones indicate moderate (≥ 60%). Individual branches are color-coded by the nature of protein domains. We characterized all BTB proteins into 11 classes. Expanded views of trees with more detail can be found in supplement Figures S3–6 [see Additional file 5, 6, 7, 8].