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Plant Physiol. 2015 Sep;169(1):803-13. doi: 10.1104/pp.15.00587. Epub 2015 Jul 6.

Rate Motifs Tune Auxin/Indole-3-Acetic Acid Degradation Dynamics.

Author information

1
Departments of Biology (B.L.M., J.M.G., M.K., A.N., A.L., J.L.N.) and Pharmacology (H.M., T.R.H., N.Z.), University of Washington, Seattle, Washington 98195;Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany (A.H., L.I.A.C.V.); andHoward Hughes Medical Institute, Chevy Chase, Maryland 20815 (N.Z.).
2
Departments of Biology (B.L.M., J.M.G., M.K., A.N., A.L., J.L.N.) and Pharmacology (H.M., T.R.H., N.Z.), University of Washington, Seattle, Washington 98195;Leibniz Institute of Plant Biochemistry, 06120 Halle (Saale), Germany (A.H., L.I.A.C.V.); andHoward Hughes Medical Institute, Chevy Chase, Maryland 20815 (N.Z.) jn7@uw.edu.

Abstract

Ubiquitin-mediated protein degradation is a common feature in diverse plant cell signaling pathways; however, the factors that control the dynamics of regulated protein turnover are largely unknown. One of the best-characterized families of E3 ubiquitin ligases facilitates ubiquitination of auxin (aux)/indole-3-acetic acid (IAA) repressor proteins in the presence of auxin. Rates of auxin-induced degradation vary widely within the Aux/IAA family, and sequences outside of the characterized degron (the minimum region required for auxin-induced degradation) can accelerate or decelerate degradation. We have used synthetic auxin degradation assays in yeast (Saccharomyces cerevisiae) and in plants to characterize motifs flanking the degron that contribute to tuning the dynamics of Aux/IAA degradation. The presence of these rate motifs is conserved in phylogenetically distant members of the Arabidopsis (Arabidopsis thaliana) Aux/IAA family, as well as in their putative Brassica rapa orthologs. We found that rate motifs can act by enhancing interaction between repressors and the E3, but that this is not the only mechanism of action. Phenotypes of transgenic plants expressing a deletion in a rate motif in IAA28 resembled plants expressing degron mutations, underscoring the functional relevance of Aux/IAA degradation dynamics in regulating auxin responses.

PMID:
26149575
PMCID:
PMC4577399
DOI:
10.1104/pp.15.00587
[Indexed for MEDLINE]
Free PMC Article

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