ARABIDILLO proteins have a novel and conserved domain structure important for the regulation of their stability

• Published in: Plant molecular biology Vol. 75; no. 1-2; pp. 77 - 92
• Main Authors: Nibau, Cândida, Gibbs, Daniel J, Bunting, Karen A, Moody, Laura A, Smiles, Emma J, Tubby, Jennifer A, Bradshaw, Susan J, Coates, Juliet C
• Format: Journal Article
• Language: English
• Published: Dordrecht Dordrecht : Springer Netherlands 2011; Springer Netherlands; Springer Nature B.V
• Subjects: Amino Acid Sequence; Arabidopsis Proteins - chemistry; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Armadillo repeats; beta Catenin - chemistry; beta Catenin - genetics; beta Catenin - metabolism; Binding Sites - genetics; Biochemistry; Biomedical and Life Sciences; Blotting, Western; Botany; Cell cycle; Conserved Sequence - genetics; F-box; F-Box Proteins - chemistry; F-Box Proteins - genetics; F-Box Proteins - metabolism; Gene Expression Regulation, Plant; Hormones; Leucine-rich repeats; Life Sciences; Models, Molecular; Molecular biology; Molecular Sequence Data; Mutation; Phylogeny; Plant biology; Plant Pathology; Plant Sciences; Proteasome Endopeptidase Complex - metabolism; Protein Binding; Protein Stability; Protein Structure, Tertiary; Proteins; Repetitive Sequences, Amino Acid; Reverse Transcriptase Polymerase Chain Reaction; Sequence Homology, Amino Acid; SKP Cullin F-Box Protein Ligases - genetics; SKP Cullin F-Box Protein Ligases - metabolism; Two-Hybrid System Techniques; Ubiquitin - metabolism; Leucine-rich repeats; Protein stability; F-box; Armadillo repeats
• ISSN: 0167-4412; 1573-5028
• DOI: 10.1007/s11103-010-9709-1

ARABIDILLO proteins are F-box-Armadillo (ARM) proteins that regulate root branching in Arabidopsis. Many F-box proteins in plants, yeast and mammals are unstable. In plants, the mechanism for this instability has not been fully investigated. Here, we show that a conserved family of plant ARABIDILLO-related proteins has a unique domain structure consisting of an F-box and leucine-rich repeats (LRRs) followed by ARM-repeats. The LRRs are similar to those found in other plant and animal F-box proteins, including cell cycle proteins and hormone receptors. We demonstrate that the LRRs are required for ARABIDILLO1 function in vivo. ARABIDILLO1 protein is unstable: we show that ARABIDILLO1 protein is associated with ubiquitin and is turned over by the proteasome. Both the F-box and LRR regions of ARABIDILLO1 appear to enable this turnover to occur. Application of known lateral root-regulating signals has no effect on ARABIDILLO1 stability. In addition, plants that lack or overexpress ARABIDILLO proteins respond normally to known lateral root-regulating signals. Thus, we suggest that the signal(s) regulating ARABIDILLO stability in vivo may be either highly specific or novel. The structural conservation between ARABIDILLOs and other plant and animal F-box proteins suggests that the stability of other F-box proteins may be controlled by similar mechanisms.