Figure 5

Co-evolution of Runx and CBFβ proteins. A) We generated the accepted organismal phylogeny relating 11 taxa for which both Runx and CBFβ sequences are available. We then inferred the evolutionary change in Runx (blue) and CBFβ (green) along each branch of this phylogeny by using the JTT matrix to calculate patristic distances. B) For each node on the tree, the evolutionary change in CBFβ and GAPDH were plotted against the evolutionary change in Runx. The regression reveals a significant and strong correlation between the evolutionary change in Runx and CBFβ (represented by squares and solid line; R² = 0.83, F_1,17 = 85.11, p < 0.0001) but not between Runx and GAPDH (circles and dashed line). The outliers (the circle and square with a Runx branch length of ~0.3) represent the divergence between the protostome ancestor and the common Caenorhabditis ancestor (see panel A). Both Runx (branch length = ~0.3) and CBFβ (branch length = ~0.44) diverged rapidly within this lineage, while GAPDH continued to evolve more slowly (equivalent branch length in GAPDH tree = ~0.05).