Mutating S590, T593, and S602 to aspartic acids also impaired phyA function. (A) Phenotypes of 4-d-old WT (Ler), phyA-1, and homozygous transgenic lines expressing WT or various mutant forms of Arabidopsis phyA (under the control of the native Arabidopsis PHYA promoter in the phyA-1 background) grown in darkness (D) or continuous FR light. (Scale bar: 2 mm.) (B) Quantitative analysis of hypocotyl lengths of the WT (Ler), phyA-1, and various transgenic lines shown in A. Error bars represent SD from 30 seedlings.