Figure 1.

Outline of the Flavonoid Metabolism in Arabidopsis.

Flavonoids are secondary metabolites derived from products of the phenylpropanoid biosynthetic pathway and the Krebs cycle. The final compounds include flavonols (colorless pigments), anthocyanins (pink and red pigments), and condensed tannins (brown pigments). The characterized enzymes are shown in boldface. The various mutants identified are noted adjacent to the step they affect, with putative regulatory loci given in parentheses. ban, banyuls; CHI, chalcone isomerase; CHS, chalcone synthase; C4H, cinnamate 4-hydroxylase; 4CL, 4-coumarate:CoA ligase; DFR, dihydroflavanol 4-reductase; F3H, flavanone 3-hydroxylase; F3′H, flavonoid 3′-hydroxylase; FLS, flavonol synthase; icx1, increased chalcone synthase expression1; LAR, leucoanthocyanidin reductase; LDOX, leucoanthocyanidin dioxygenase; PAL, phenylalanine ammonia-lyase; tt, transparent testa; ttg, transparent testa glabra.