ARABIDILLO proteins have a novel and conserved domain structure important for the regulation of their stability.
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.
School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK.
Cândida
C
Nibau
Daniel J
DJ
Gibbs
Karen A
KA
Bunting
Laura A
LA
Moody
Emma J
EJ
Smiles
Jennifer A
JA
Tubby
Susan J
SJ
Bradshaw
Juliet C
JC
Coates
D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D017124:Conserved Sequence / Q000235:genetics*; D044783:F-Box Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D020449:Repetitive Sequences, Amino Acid; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044843:SKP Cullin F-Box Protein Ligases / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism; D051176:beta Catenin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
C120363:ASK1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D044783:F-Box Proteins; D025801:Ubiquitin; C508786:arabidillo-1 protein, Arabidopsis; D051176:beta Catenin; C484058:ASK2 protein, Arabidopsis; D044843:SKP Cullin F-Box Protein Ligases; D046988:Proteasome Endopeptidase Complex