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. Homodimer. Expressed in root vasculature and meristems, cotyledons, flowers, siliques, and leaf trichomes. Localized in the interfascicular/vascular cambia and developing xylem. In flowers, expressed in the vasculature of sepals, petals, stamen filaments, and the gynoecium stylar region. In siliques, observed in the stigmatic region and epidermal layers. Belongs to the plant dirigent protein family.