A zinc finger protein gene ZFP5 integrates phytohormone signaling to control root hair development in Arabidopsis

Although root hair development in Arabidopsis thaliana has been extensively studied, it remains unknown whether the zinc finger proteins, the largest family of transcription factors in plants, are involved in this process. Here we report that the C2H2 zinc finger protein ZINC FINGER PROTEIN 5 (ZFP5) is a key regulator of root hair initiation and morphogenesis in Arabidopsis. ZFP5 is mainly expressed in root and preferentially in root hair cells. Using both zfp5 mutants and ZFP5 RNAi lines, we show that reduction in ZFP5 function leads to fewer and much shorter root hairs compared to wild-type. Genetic and molecular experiments demonstrate that ZFP5 exerts its effect on root hair development by directly promoting expression of the CAPRICE (CPC) gene. Furthermore, we show that ZFP5 expression is induced by cytokinin, and that ZFP5 mediates cytokinin and ethylene effects on the formation and growth of root hairs. These results suggest that ZFP5 integrates various plant hormone cues to control root epidermal cell development in Arabidopsis.