FIGURE 2. Flavonoid biosynthetic pathway. Enzymes involved in anthocyanin biosynthesis and side branches leading to related flavonoid pathways are shown. PAL, phenylalanine ammonialyase; C4H, cinnamate 4-hydroxylase; 4Cl, coumarate: CoA ligase; CHS, chalcone synthase; CHI, chalcone isomerase; F3H, flavanone 3β-hydroxylase; F3′H, dihydroflavonol 3′ hydroxylase; F3′5′H, dihydroflavonol 3′5′ hydroxylase; DFR, dihydroflavonol reductase; ANS, anthocyanidin synthase; UF3GT, UDP-glucose flavonol 3-0-glucosyl transferase; RT, rhamnosyl transferase.
anthocyanin pigments are therefore important to reproductive success and hence to gene transmission. In addition to pigment production, several side branches of the pathway also produce compounds that are important in plant disease defense, pollen viability, microbial interactions, and UV protection (Koes et al., 1994). The flavonoid pathway has a pleiotropic role in plants, and one must consider that a single mutation in the