Figure 3.

Induction of FB in HL depends on carbon fixation, TP export, and carbohydrates.

(A) Anthocyanin accumulation in Col-0 (gray) and tpt-2 (yellow) in buffer containing different concentrations of SOR or SUC. Seedlings were transferred to the buffer at the end of the night and exposed to HL for 24 h.

(B and C) Relative expression of PAP1(B) and (C)LDOX in Col-0 (gray), adg1-1 (blue), and adg1-1 tpt-2 (green) after 8 h HL treatment. Gene expression was calculated using the 2^−ΔΔCt method relative to Col-0 after 8 h HL with SAND as the reference gene.

(D and E) Anthocyanin content (expressed as cyanidin equivalents) (D) and (E) phenotype of WT and mutant plants exposed to 24 h HL. Left column shows the adaxial view and right column the abaxial view of 2 individual plants.

(F and G) Relative expression of PAP1(F) and (G)LDOX in Col-0 before incubation (EoN, t0, gray) in 400 ppm CO₂ (light pink) or 50 ppm CO₂ (purple). Leaves were mounted in a LI-COR device and incubated for 4 h at 500 μmol photons m⁻² s⁻¹. Gene expression was calculated using the 2^−ΔΔCt method relative to expression at t0 with SAND as the reference gene. Five-week-old rosette plants were used, and each data point represents 1 leaf sample from independent plants.

(H) Anthocyanin content (expressed as cyanidin equivalents) after 24 h HL in Col-0 incubated in buffer with 90 mM SOR or SUC in the absence or presence of increasing amounts of DCMU (0–10 μM).

(I) Anthocyanin content (expressed as cyanidin equivalents) after 24 h HL in Col-0 and adg1-1 incubated in buffer with 90 mM SOR or SUC in the absence or presence of 10 μM DCMU.

(J) Same conditions as in (I), but samples were harvested after 8 h HL exposure. Gene expression was calculated using the 2^−ΔΔCt method relative to Col-0 before the transfer to incubation buffer, and SAND was used as the reference gene. The dashed lines in (J) and (K) show the mean anthocyanin content at t(0) in Col-0. All values are means ± standard deviations.

Statistical significance of differences between WT/control and mutants/treatment was calculated using 1-way ANOVA relative to Col-0 after 8 h HL (in B and C, Dunnett’s multiple comparisons test, n ≥ 3) or 24 h HL (in D, Tukey’s multiple comparisons test, n = 3) or to expression values before incubation at different CO₂ concentrations (t0 in F and G, Dunnett’s multiple comparisons test, n = 6) or 2-way ANOVA (Tukey’s multiple comparisons test in A and H–J, n = 3). Letters indicate significant differences at p ≤ 0.01. Values are means ± standard deviations.