The F-box protein AFF1 regulates ARF protein accumulation to regulate auxin response

Abstract

Auxin critically regulates nearly every aspect of plant growth and development. Auxin-driven transcriptional responses are mediated through the AUXIN RESPONSE FACTOR (ARF) family of transcription factors. Although ARF protein stability is regulated via the 26S proteasome, molecular mechanisms underlying ARF stability and turnover are unknown. Here, we report the identification and functional characterization of an F-box E3 ubiquitin ligase, which we have named AUXIN RESPONSE FACTOR F-BOX1 (AFF1). AFF1 directly interacts with ARF19 and regulates its accumulation. Mutants defective in AFF1 display ARF19 protein hyperaccumulation, attenuated auxin responsiveness, and developmental defects. Together, our data suggest a new mechanism, namely control of ARF protein stability, in regulating auxin response.