Fig 1.

Biosynthesis of flavonoids and isoflavonoids, indicating competing pathways for naringenin in transgenic Arabidopsis expressing IFS. Formation of liquiritigenin requires the activity of a chalcone reductase (CHR) that co-acts with chalcone synthase (CHS) to form isoliquritigenin. CHR is present in legumes, but not in Arabidopsis. Daidzein cannot be made in Arabidopsis without introduction of CHR and a legume CHI. Steps blocked in the tt3, tt5, and tt6 mutations are shown. F3H, flavonoid 3-hydroxylase; DFR, dihydroflavonol reductase.