a, Multi-alignment of ZPR-type sequences from eight different angiosperm species (Aquilegia coerulea (Ac), Amborella trichopoda (Amtr), A. thaliana (At), Daucus carota (Dc), Medicago truncatula (Mt), Oryza sativa (Os), Populus trichocarpa (Pt), S. lycopersicum (Sl) and Sorghum bicolor (Sb)). At least one ZPR2-type and one ZPR3-type sequence was identified in all species that we considered. All ZPR2-type proteins have a Cys residue at the second position of the N-terminal domain. Amino acid position is displayed on top of each alignment, using A. thaliana ZPR2 as a reference. b, Molecular phylogenetic analysis by the maximum likelihood method. The tree with the highest log-likelihood (−1,500.12) is shown. The percentage of trees in which the associated taxa clustered together is shown next to the branches. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 28 protein sequences (listed in Supplementary Table 4).