Mutations in the TIR1 Auxin Receptor That Increase Affinity for Auxin/Indole-3-Acetic Acid Proteins Result in Auxin Hypersensitivity

Yu, Hong; Moss, Britney L.; Jang, Seung-Hee; Prigge, Michael J.; Klavins, Eric; Nemhauser, Jennifer L.; Estelle, Mark

doi:10.1104/pp.113.215582

Cited by 62 publications

(52 citation statements)

References 40 publications

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“…Recently, two new tir1 mutants were identified in a yeast two-hybridbased screen. The tir1D170E and tir1M473L mutations increase the affinity of TIR1 for the Aux/IAA proteins, whereas plants expressing tir1D170E and tir1M473L transgenes show an auxin hypersensitive phenotype and developmental defects (Yu et al, 2013).…”

Section: Scf Tir1/afbs and Auxin Perceptionmentioning

confidence: 99%

SCF^TIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

2015

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Auxin regulates a vast array of growth and developmental processes throughout the life cycle of plants. Auxin responses are highly context dependent and can involve changes in cell division, cell expansion, and cell fate. The complexity of the auxin response is illustrated by the recent finding that the auxin-responsive gene set differs significantly between different cell types in the root. Auxin regulation of transcription involves a core pathway consisting of the TIR1/AFB F-box proteins, the Aux/IAA transcriptional repressors, and the ARF transcription factors. Auxin is perceived by a transient coreceptor complex consisting of a TIR1/AFB protein and an Aux/IAA protein. Auxin binding to the coreceptor results in degradation of the Aux/ IAAs and derepression of ARF-based transcription. Although the basic outlines of this pathway are now well established, it remains unclear how specificity of the pathway is conferred. However, recent results, focusing on the ways that these three families of proteins interact, are starting to provide important clues.

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Section: Scf Tir1/afbs and Auxin Perceptionmentioning

confidence: 99%

SCF^TIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

2015

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“…The KR Rate Motif Does Not Alter IAA Affinity for the TIR1 F-Box Protein Enhancing TIR1 affinity for Aux/IAAs can accelerate Aux/IAA degradation rate (Yu et al, 2013). To test whether rate motifs act by influencing Aux/IAA binding to TIR1, we used two measures of interaction strength: in vitro competition binding experiments and yeast two-hybrid assays.…”

Section: Rate Motifs Tune Aux/iaa Degradation Rate In Plant Rootsmentioning

confidence: 99%

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

Moss

Mao

Guseman³

et al. 2015

Plant Physiol.

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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 auxininduced 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.

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“…Both clones were sequence verified. pGILDA-TIR1 and pGILDA-IAA7 have been previously described (Yu et al, 2013).…”

Section: Molecular Cloning and Plant Materialsmentioning

confidence: 99%

Lysine Residues Are Not Required for Proteasome-Mediated Proteolysis of the Auxin/Indole Acidic Acid Protein IAA1

Gilkerson

Kelley²,

Tam

et al. 2015

Plant Physiol.

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Although many ubiquitin-proteasome substrates have been characterized in plants, very little is known about the corresponding ubiquitin attachment(s) underlying regulated proteolysis. Current dogma asserts that ubiquitin is typically covalently attached to a substrate through an isopeptide bond between the ubiquitin carboxy terminus and a substrate lysyl amino group. However, nonlysine (non-Lys) ubiquitin attachment has been observed in other eukaryotes, including the N terminus, cysteine, and serine/threonine modification. Here, we investigate site(s) of ubiquitin attachment on indole-3-acetic acid1 (IAA1), a short-lived Arabidopsis (Arabidopsis thaliana) Auxin/indole-3-acetic acid (Aux/IAA) family member. Most Aux/IAA proteins function as negative regulators of auxin responses and are targeted for degradation after ubiquitination by the ubiquitin ligase SCF TIR1/AFB (for S-Phase Kinase-Associated Protein1, Cullin, F-box [SCF] with Transport Inhibitor Response1 [TIR1]/Auxin Signaling F-box [AFB]) by an interaction directly facilitated by auxin. Surprisingly, using a Histidine-Hemaglutinin (HIS 6x -HA 3x ) epitope-tagged version expressed in vivo, Lys-less IAA1 was ubiquitinated and rapidly degraded in vivo. Lys-substituted versions of IAA1 localized to the nucleus as Yellow Fluorescent Protein fusions and interacted with both TIR1 and IAA7 in yeast (Saccharomyces cerevisiae) two-hybrid experiments, indicating that these proteins were functional. Ubiquitination on both HIS 6x -HA 3x -IAA1 and Lys-less HIS 6x -HA 3x -IAA1 proteins was sensitive to sodium hydroxide treatment, indicative of ubiquitin oxyester formation on serine or threonine residues. Additionally, baseresistant forms of ubiquitinated IAA1 were observed for HIS 6x -HA 3x -IAA1, suggesting additional lysyl-linked ubiquitin on this protein. Characterization of other Aux/IAA proteins showed that they have diverse degradation rates, adding additional complexity to auxin signaling. Altogether, these data indicate that Aux/IAA family members have protein-specific degradation rates and that ubiquitination of Aux/IAAs can occur on multiple types of amino residues to promote rapid auxin-mediated degradation.The ubiquitin-proteasome system (UPS) is the major pathway for degradation of regulatory proteins in eukaryotic cells. Ubiquitin (UBQ), an approximately 8-kD protein, is covalently ligated to substrates, often with additional UBQs linked to each other to form a polyubiquitin chain. UBQ chains with specific UBQ-UBQ linkages facilitate interaction between substrates and the 26S proteasome, a multifunctional protease. Ligation of UBQ to substrates requires three enzymatic activities in series: E1 UBQ-activating enzyme, E2 UBQ-conjugating enzyme, and an E3 ubiquitin ligase. UBQ attachment begins with the ATP-dependent covalent linkage of UBQ through its carboxy terminus to the E1 active-site Cys. The E1 then transfers thioester-linked activated UBQ to the E2 active-site Cys, forming a UBQ-charged E2. The UBQ-charged E2 interacts with an E3. E3 ligases bind ...

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Mutations in the TIR1 Auxin Receptor That Increase Affinity for Auxin/Indole-3-Acetic Acid Proteins Result in Auxin Hypersensitivity

Cited by 62 publications

References 40 publications

SCF^TIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

SCF^TIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

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

Lysine Residues Are Not Required for Proteasome-Mediated Proteolysis of the Auxin/Indole Acidic Acid Protein IAA1

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Mutations in the TIR1 Auxin Receptor That Increase Affinity for Auxin/Indole-3-Acetic Acid Proteins Result in Auxin Hypersensitivity

Cited by 62 publications

References 40 publications

SCFTIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

SCFTIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

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

Lysine Residues Are Not Required for Proteasome-Mediated Proteolysis of the Auxin/Indole Acidic Acid Protein IAA1

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SCF^TIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development

SCF^TIR1/AFB-Based Auxin Perception: Mechanism and Role in Plant Growth and Development