GCNA and YABBY HMG boxes are more closely related to each other than they are to any other type of HMG box, either within plants or across eukarya.

(A) Maximum likelihood tree of all known classes of plant HMG boxes. GCNA proteins in green algae and spikemoss (Selaginella, a basal land plant) are yellow. YABBY proteins in green algae (Spirogyra), Selaginella, and seed plants are pink. The six non-GCNA/YABBY types of plant HMG boxes are gray. (B) Maximum likelihood tree of all major classes of animal and fungal HMG boxes. The two-helix HMG boxes of GCNAs and YABBYs are more related to each other than they are to the first two helices of any other type of HMG box in animals or fungi. Colors are as in (A), with the addition of vertebrate GCNA proteins (orange). Non-GCNA/YABBY classes of HMG boxes are gray. Bootstrap values over 600 (out of 1000) are indicated. Trees were constructed using PhyML.