Unrooted phylogenetic tree of dirigent and dirigent-like family proteins (Pfam PF03018). The subfamily nomenclature of Ralph et al. (2) is maintained, with some families split where clear divisions were apparent (e.g. DIR-a1 and DIR-a2). Proteins whose functional characterization has been described in the literature are indicated (e.g. DRR206 (12, 14), a (+)-pinoresinol–forming DP from pea (P. sativum), in the Dir-a1 subfamily; AtDIR6 (8, 9, 13), a (–)-pinoresinol–forming DP from A. thaliana, in the Dir-a2 subfamily; GePTS1 (19) and PsPTS1, medicarpin-forming DPs from licorice (G. echinata) and pea, respectively, in the Dir-b/d subfamily; GhDIR4 (16, 17), an aromatic diterpenoid ((+)-gossypol–forming) DP from cotton (G. hirsutum); and AtDIR10 (20), a Casparian band lignin-forming DP from A. thaliana, in the Dir-e subfamily). The narrow distributions of sequences from gymnosperms, lycophytes, and bryophytes are easily discernable and contrast with the broad distribution of angiosperm dicots and even broader distribution of extant angiosperm monocots (mainly crop grasses). Ends of each branch of the tree are colored for different land plant families as indicated (e.g. light blue ends indicate lycophytes).