Evolutionary model of urea carboxylase and urea amidolyase in fungi. (A) The evolution of the two types of bacterial urea carboxylases, UC1 and UC2, and the subsequent transfer of those genes to fungi and green algae. The arrows represent possible horizontal gene-transfer events. Dashed arrows indicate that both horizontal transfer and vertical transmission are possible. (B) Acquisition and loss events of the urea amidolyase and related proteins inferred within fungal evolution. The fungal consensus phylogeny and the presence/absence table for five proteins are the same as Figure 2. Within the tree, the colored symbols indicate gene-acquisition events while the grey symbols indicate the deletion of that gene.