In Arabidopsis (Arabidopsis thaliana), root hairs are formed in cell files over the cleft of underlying cortex cells. This pattern is established by a well-known gene regulatory network of transcription factors. In this study, we show that WRKY75 suppresses root hair development in nonroot hair files and that it represses the expression of TRIPTYCHON and CAPRICE. The WRKY75 protein binds to the CAPRICE promoter in a yeast one-hybrid assay. Binding to the promoter fragment requires an intact WRKY protein-binding motif, the W box. A comparison of the spatial expression of WRKY75 and the localization of the WRKY75 protein revealed that WRKY75 is expressed in the pericycle and vascular tissue and that the WRKY75 RNA or protein moves into the epidermis.