Figure 6.

Role of AUG-Stop in B-Dependent Downregulation of SKU5.

(A) mRNA accumulation in Col-0 roots under 100 µM B (+B) and 0.3 µM B (−B). Means ± sd of relative mRNA accumulation (n = 3) are shown. Asterisk indicates significant reduction under +B condition (P < 0.05).

(B) Schematic representation of the 5′-SKU5(−206):LUC RNA. Open boxes represent uORFs. 5′-SKU5(−206):LUC RNA was translated in WGE, and means ± sd of relative LUC activities (n = 3) are shown. Asterisks indicate significant reductions of relative reporter activity in RNA carrying AUGUAA (P < 0.05).

(C) and (D) Primer extension (C) and toeprint (D) analyses in WGE with 300 µM B (+B) or without B supplementation (−B). Signals are enlarged below the main image of the AUGUAA lane, and means ± sd of relative signal intensities are shown (n = 3). Asterisks indicate significant differences (P < 0.05).

(E) Nucleotide sequence around AUG-stop and the positions of primer extension (magenta) and toeprint signals (green) are marked. Ribosome occupation of RNA having the AUG codon positioned at the P-site is shown.

(F) Arabidopsis Wassilewskija (Ws) and sku5 mutant plants were grown under 0.3 µM B (−B) or 100 µM B (+B) conditions for 10 d, and root length was measured. Means ± sd of root length (n = 5 to 10) are shown. Asterisks indicate significant reductions in root lengths of sku5 mutants compared with wild-type Wassilewskija (P < 0.05). Bar = 10 mm.