Figure 1.

Morphological and Biochemical Analysis of rep1 Mutant under Various Light Conditions.

(A) Measurement of hypocotyl lengths. The seedlings were grown under various light conditions for 4 days. The hypocotyl lengths of the wild type (WT) and mutants were normalized to their respective hypocotyl lengths in darkness. The average length of the dark-grown seedlings was 13.61, 12.45, 14.20, 12.52, and 13.72 mm for the wild-type, phyB-9, phyA-211, rep1-1, and rep1-2 seedlings, respectively. The fluence rates used were 2.5, 7, 2, 10, and 15 μmol m⁻² sec⁻¹ for FR low, FR high, R low, R high, and white light (WL), respectively. Each measurement was performed with at least 25 seedlings. The error bars indicate standard deviations.

(B) Comparison of seedling morphology of the wild type (WT; top) and rep1-1 mutant (bottom) that were grown for 4 days under the light conditions indicated in (A). Note that the cotyledon expansion of the rep1-1 mutant under FR low conditions is partially defective compared with that of the wild type. .

(C) Fluence rate responses of inhibition of hypocotyl elongation under FR light. The seedlings were grown for 4 days under various fluence rates of FR light (0, 2.5, 4.4, 8.8, 19, and 45 μmol m⁻² sec⁻¹). The data shown are averages of relative hypocotyl lengths from at least 20 seedlings, normalized to their respective hypocotyl length in darkness. The error bars indicate standard deviations. s, sec; WT, wild type.

(D) End-of-day (EOD) FR responses of the wild type and mutants. The mean hypocotyl lengths from at least 20 seedlings are shown. Hatched bars, no EOD-FR treatments; black bars, EOD-FR treatments. The error bars indicate standard deviations. WT, wild type.

(E) Immunoblot analysis of PhyA. The seedlings were grown in darkness for 4 days (D) and then irradiated with R light, 10 μmol m⁻² sec⁻¹, for 6 hr (R). The specificity of the antibody to PhyA was verified by the absence of signal from the phyA-211 mutant.