Figure 1

Simplified, schematic representation of flavonoid biosynthesis in A. thaliana with a focus on proanthocyanidins. Essential steps of the flavonoid biosyntheses leading to proanthocyanidins (PAs) in the seed are presented. Enzymes and transcriptional regulators (grey shaded) are indicated by bold, capital letters; corresponding mutant plant lines are in italics. Dashed arrows tag multiple steps which are not fully understood. The question mark indicates a limited knowledge of this biosynthetic step and a restricted understanding of the involvement of the associated factors. Abbreviations are as follows: ANR/BAN anthocyanidin reductase, AHA10 P-type H⁺-ATPase, CHS chalcone synthase, CHI chalcone isomerase, DFR dihydroflavonol 4-reductase, EGL3 enhancer of glabra3, F3 H flavanone 3β-hydroxylase, F3'H flavonoid 3'-hydroxylase, GL3 glabra3, GST glutathione S transferase, LAC laccase-like, LDOX leucoanthocyanidin dioxygenase, MATE multidrug and toxic compound extrusion-type transporter, PAP production of anthocyanin pigments, TT transparent testa, TTG transparent testa glabra, UGTs UDP dependent glycosyltransferases. Modified from [1, 67, 68].