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Nat Commun. 2017 Jun 7;8:15706. doi: 10.1038/ncomms15706.

Variation in auxin sensing guides AUX/IAA transcriptional repressor ubiquitylation and destruction.

Author information

1
Department of Molecular Signal Processing, Leibniz Institute of Plant Biochemistry (IPB), Halle (Saale) D-06120, Germany.
2
Institute of Agricultural and Nutritional Sciences, Martin Luther University Halle-Wittenberg, Halle (Saale) D-06120, Germany.
3
Institute of Synthetic Biology, University of Düsseldorf, Düsseldorf D-40225, Germany.
4
Spemann Graduate School of Biology and Medicine (SGBM), University of Freiburg, Freiburg D-79104, Germany.
5
Proteome Analytics Research Group, Leibniz Institute of Plant Biochemistry (IPB), Halle (Saale) D-06120, Germany.
6
Independent Junior Research Group Ubiquitination in Immunity, Leibniz Institute of Plant Biochemistry (IPB), Halle (Saale) D-06120, Germany.
7
Cluster of Excellence on Plant Science (CEPLAS), University of Düsseldorf, Düsseldorf D-40225, Germany.

Abstract

Auxin is a small molecule morphogen that bridges SCFTIR1/AFB-AUX/IAA co-receptor interactions leading to ubiquitylation and proteasome-dependent degradation of AUX/IAA transcriptional repressors. Here, we systematically dissect auxin sensing by SCFTIR1-IAA6 and SCFTIR1-IAA19 co-receptor complexes, and assess IAA6/IAA19 ubiquitylation in vitro and IAA6/IAA19 degradation in vivo. We show that TIR1-IAA19 and TIR1-IAA6 have distinct auxin affinities that correlate with ubiquitylation and turnover dynamics of the AUX/IAA. We establish a system to track AUX/IAA ubiquitylation in IAA6 and IAA19 in vitro and show that it occurs in flexible hotspots in degron-flanking regions adorned with specific Lys residues. We propose that this signature is exploited during auxin-mediated SCFTIR1-AUX/IAA interactions. We present evidence for an evolving AUX/IAA repertoire, typified by the IAA6/IAA19 ohnologues, that discriminates the range of auxin concentrations found in plants. We postulate that the intrinsic flexibility of AUX/IAAs might bias their ubiquitylation and destruction kinetics enabling specific auxin responses.

PMID:
28589936
PMCID:
PMC5467235
DOI:
10.1038/ncomms15706
[Indexed for MEDLINE]
Free PMC Article

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