Fig. 7. Effects of the SAC51 5'-leader on GUS reporter gene expression. (A) The GUS gene constructs consisting of the SAC51 promoter with either wild-type SAC51 or the mutant sac51-d 5'-leader sequences and the GUS coding sequence. White arrows represent the SAC51 promoter, boxes indicate exons, lines indicate introns; gray boxes represent uORFs and black blocks correspond to the GUS-coding sequence. (B-F) GUS staining (blue) in transgenic plants harboring the SAC51-GUS construct (left) or the sac51-d-GUS construct (right). Sixteen-day-old seedlings (B), inflorescences (C), young rosette leaves (D), roots (E), and mature embryos (F) are shown. Scale bars: B,C, 5 mm; D,E, 1 mm; F, 100 µm. (G) The relative GUS translational efficiency of SAC51-GUS and sac51-d-GUS constructs in wild-type (WT), acl5-1 and sac51-d acl5-1 backgrounds, and that of the sac51-C549A-GUS (C549A) construct in the wild-type background. The levels of GUS activity and GUS mRNA in the SAC51-GUS transgenic line in the wild-type background were set at 1.0. The GUS translational efficiencies were calculated as the GUS activity divided by the GUS mRNA level for each plant. The GUS mRNA levels were normalized to the ACT8 level in each sample. Bars show mean±s.d. (n=3). (H) Nucleotide and amino acid changes at the sac51-d mutation site in SAC51-GUS, sac51-d-GUS and sac51-C549A-GUS constructs. Nucleotide and amino acid changes are in bold.