Dirigent proteins impart stereoselectivity on the phenoxy radical-coupling reaction, yielding optically active lignans from two molecules of coniferyl alcohol in the biosynthesis of lignans, flavonolignans, and alkaloids and thus plays a central role in plant secondary metabolism (By similarity). Also involved in the biosynthesis of etoposide, a chemotherapeutic compound of the topoisomerase inhibitor family (PubMed:26359402). Aromatic compound metabolism; phenylpropanoid biosynthesis. Homodimer. Expressed in rhizomes, stems, and leaves. Transiently induced after wounding and by jasmonic acid (MeJA) (PubMed:26359402, PubMed:23653238). After an exposition to UV-light, first transiently induced before fading out (PubMed:23653238). Combinatorially expression of Sinopodophyllum hexandrum (mayapple) genes of the podophyllotoxin pathway (e.g. DIR, PLR, SDH, CYP719A23, OMT3, CYP71CU1, OMT1, 2-ODD, CYP71BE54 and CYP82D61) in Nicotiana benthamiana (tobacco) results in the production of the chemotherapeutic compound etoposide. Belongs to the plant dirigent protein family.