Figure 1.

Schematic overview of the flavonoid biosynthetic pathway and regulation in tomato fruit. The amino acid l-Phe is transformed into naringenin chalcone by the action of PAL, C4H, 4CL, and CHS enzymes. Naringenin chalcone is the precursor of different flavonoid classes: chalcones, flavonones, flavones, isoflavones, dihydroflavonols, and flavonols. SlMYB12 TF is the main activator of the flavonol biosynthetic branch to act on PAL, 4CL, CHS, CHI, F3H, and FLS genes (Adato et al., 2009; Ballester et al., 2010). 3GT, 3-O-GLYCOSYL TRANSFERASE; RT, RHAMNOSYL TRANSFERASE.