Figure 5.

Alternative models depicting the evolution of the plant P3 protein. Model 1. Duplication and divergence of the ancestral L12-like gene occurred very early in the eukaryotic lineage resulting in P1, P2, and P3 type proteins in ancestral eukaryotes. Contemporary plants have retained the P3 gene, whereas the specific loss of P3 from other contemporary eukaryotes is necessary to explain the absence of P3 in these species. Model 2. Duplication and divergence of the ancestral L12-like gene occurred very early in the eukaryotic lineage to produce P1 and P2 type P-proteins in ancestral eukaryotes. Further duplication and divergence within the plant lineage produced the P3 seen in modern plants.