CalS5 is a direct target of ARF17. A, Potential ARF-binding sites in the 1.5-kb CalS5 promoter. The black box indicates the position of the canonical AuxRE sequence (GAGACA). The black lines at top indicate fragments amplified in Chip-PCR assays. B, Real-time PCR of promoter fragments in ChIP using ARF17-GFP flower buds. Enrichment was only observed when the fragment containing the AuxRE was amplified when affinity-purified GFP antibody was used. C, EMSA for ARF17 binding to the CalS5 gene promoter. GST-ARF17 protein was mixed with a biotin-labeled 64-bp probe containing the AuxRE and 5- or 25-fold unlabeled probe as competitor. The arrowhead indicates a shift band. FP, Free probe.