The E3 Ubiquitin Ligase AFF1 targets ARF19 to the proteasome

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, mild auxin resistance, and developmental defects. Together, our data suggest a new mechanism, namely control of ARF protein stability, in regulating auxin responsiveness. Overall design: This RNAseq experiment examined 3 genotypes (Col-0, aff1-1, aff1-2) of 4 day old Arabidopsis thaliana seedlings under two conditions (mock treated or 2 hour treatment with 10mM indole-3-acetic acid (IAA)). The RNA was isolated from whole seedlings. There were three replicates carried out for each genotype/treatment combination yeilding a total of 18 samples. The aff1-2 line is Salk_083453.