Figure 5.

Conserved amino acids and the stop codon position of the Suc control peptide are necessary for Suc-induced repression of translation. Relative normalized LUC activity levels of 10-d-old seedlings transformed with the 35S:bZIP11 5′ leader:LUC construct or versions with mutated 5′ leaders. Following transformation, seedlings were incubated for 24 h in medium containing either no Suc (white bars) or 6% Suc (gray bars). Means of at least three biological replicates are presented. Error bars represent sd from the mean. Two or more independent experiments were performed with essentially similar results. A, The amino acid sequence of the 28 C-terminal amino acids of the SC-peptide or mutated versions used for transformation experiments are indicated on the left. Changed amino acids are indicated in underlined lowercase letters. B, Schematic drawings of constructs used for transient expression experiments are indicated to the left. Rectangles represent ORFs. Dark gray rectangles represent uORF2. The mutated 5′ leaders encode either a shorter uORF2, early stop (the last two residues missing); a longer uORF2, late stop (13 residues added after the intact uORF2 sequence); or a combinatorial mutant, double frame shift, in which a frame shift mutation (Fig. 3) is combined with another frame shift mutation at the end of uORF2. This latter construct encodes a uORF2 peptide in which only the first two and last two residues are the same as in the wild-type counterpart. WT, Wild type.