Fig. 2.

Proposed biosynthetic relationships among aurones, auronidins, and anthocyanidins and comparison of the UV/visible-light spectra of corresponding glycosides. (A) Marchantia plants with a knockout mutation of the single chi gene showed no detectable flavones but were unaltered in auronidin production compared with WT plants. Plants with a knockout mutation of the candidate ppo aurone biosynthetic gene showed reduced auronidin content but were unaltered in flavone production. (B) Structures and corresponding UV/visible-light spectra recorded in acidified methanol of an aurone, aureusidin 4-glucoside (3) (λ_max = 402 nm); an auronidin, auronidin 4-neohesperidoside (1) (λ_max = 495 nm); and an anthocyanin, cyanidin 3-glucoside (4) (λ_max = 529 nm).