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

Abstract

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.

The Subcellular Localization of Tubby-Like Proteins and Participation in Stress Signaling and Root Colonization by the MutualistPiriformospora indica

“…We were unable to detect the accumulation of full-length AtTLPs fused to GFP in Arabidopsis by confocal laser-scanning microscopy. This suggests a high instability of these proteins, as reported for other FB proteins (Nibau et al, 2011). Since we detected a full-length AtTLP3-GFP fusion protein in N. benthamiana, the degradation of AtTLPs is executed apparently by specific proteases (Fig.…”

Comprehensive Expression Analysis of Rice Armadillo Gene Family During Abiotic Stress and Development

“…Recent finding suggests that homologues of these proteins are conserved across plants species exhibiting novel and overlapping functions. 37,38 Interestingly, some of the OsARMs ( OsPUB28 , OsARM14 , OsPUB75 ) were found to be showing elevated expression under developmental conditions but a significant down-regulation under stress conditions. Another U-box/ARM gene ( OsPUB6) , which was found to be highly, expressed under drought and salt stress conditions in the microarray analysis, share sequence similarity with Arabidopsis AtPUB18.…”

AtMYB93is an endodermis-specific transcriptional regulator of lateral root development in arabidopsis

“…28 ARABIDILLOs are F-box proteins, meaning they are implicated in proteasomal degradation of proteins. 29 Thus, we initially hypothesized that ARABIDILLOs might promote LR development through targeting a negative regulator of LR development -e.g., AtMYB93 -for degradation 26,27 ( Fig. 2A).…”

“…ARABIDILLOs are "intrinsic" LR regulators, which promote LR development independently from any known hormones or environmental cues. 26,27 Despite their rooting function, ARABIDILLO homologues are also found in early evolving plants that lack branched root systems. 28 ARABIDILLOs are F-box proteins, meaning they are implicated in proteasomal degradation of proteins.…”