Nucleo-cytoplasmic partitioning of ARF proteins controls auxin responses in Arabidopsis thaliana

The phytohormone auxin plays crucial roles in nearly every aspect of plant growth and development. The AUXIN RESPONSE FACTOR (ARF) family of transcription factors regulates auxin-responsive gene expression and exhibit nuclear localization in regions of high auxin responsiveness. Here we show that activating ARF7 and ARF19 proteins accumulate in micron-sized assemblies within the cytoplasm of tissues with attenuated auxin responsiveness. The intrinsically disordered middle region and the folded PB1 interaction domain of ARFs drive protein assembly formation. Mutation of a single lysine within the PB1 domain abrogates cytoplasmic assemblies, promotes ARF nuclear localization, and results in an altered transcriptome and morphological defects. Our data suggest a model in which ARF nucleo-cytoplasmic partitioning regulates auxin responsiveness, thus providing a mechanism for cellular competence for auxin signaling. RNA-seq analysis of Col-0 (Wt), Col-0 carrying UBQ10:YFP-ARF19, and Col-0 carrying UBQ10:YFP-ARF19K962A in the absence and presence of auxin treatment.