Figure 3.

Reduced levels of flavonoids in the stem of low-R:FR-treated plants. The chart shows the steps of lignin and flavonoid (anthocyanin, flavonol) biosynthesis catalyzed by enzymes encoded by genes showing significant expression responses to R:FR. The expression in the stem and leaf of plants treated for 4 d with low R:FR compared with their high-R:FR controls and/or in the stem of seedlings exposed for 1 or 4 h to low R:FR and subsequently transferred back to high R:FR is shown when significant differences were observed (data are from Supplemental Tables S1 and S2). The levels of lignin, kaempferol, rutin, quercetin, and anthocyanin in plants treated for 4 d with low R:FR compared with their high-R:FR controls are indicated (data are means ± se of four to 12 plant replicates, and significant effects of low compared with high R:FR are indicated [t test, * P < 0.05, ** P < 0.01]). ANS, Anthocyanin synthase; C4H, transcinnamate 4-monooxygenase; CHI, chalcone isomerase-like protein; CHS, chalcone synthase; DFR, dihydroflavonol 4-reductase; F3H, flavanone 3β-hydroxylase; FLS, flavonol synthase; FW, fresh weight; IFR, isoflavone reductase; HQT, hydroxycinnamoyl-CoA quinate transferase; RT, rhamnosyltransferase; UFGT, flavonoid 3-glucosyltransferase; UGG, UDP-Glc:glucosyltransferase. The chart is based on the BRENDA database (http://www.brenda-enzymes.info; Scheer et al., 2011).