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New tangles in the auxin signaling web.

Wright RC, Nemhauser JL - F1000Prime Rep (2015)

Bottom Line: This potential combinatorial diversity in signaling pathways likely contributes to the myriad of context-specific responses to auxin.Recent structures of several domains from ARF proteins have exposed new modes of ARF dimerization, new models for ARF-AuxRE specificity, and the strong likelihood of larger order complexes formed by ARF and Aux/IAA homo- and heteromultimerization.Preliminary experiments support a role for these novel interactions in planta, further increasing the potential architectural complexity of this seemingly simple pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Washington, Seattle Washington 98195 USA.

ABSTRACT
Plants use auxin to relay critical information that shapes their growth and development. Auxin perception and transcriptional activation are mediated by the degradation of Aux/IAA repressor proteins. Degradation of Aux/IAAs relieves repression on Auxin Response Factors (ARFs), which bind DNA sequences called Auxin Response Elements (AuxREs). In most higher plant genomes, multiple paralogs exist for each part of the auxin nuclear signaling pathway. This potential combinatorial diversity in signaling pathways likely contributes to the myriad of context-specific responses to auxin. Recent structures of several domains from ARF proteins have exposed new modes of ARF dimerization, new models for ARF-AuxRE specificity, and the strong likelihood of larger order complexes formed by ARF and Aux/IAA homo- and heteromultimerization. Preliminary experiments support a role for these novel interactions in planta, further increasing the potential architectural complexity of this seemingly simple pathway.

No MeSH data available.


Related in: MedlinePlus

Domain diagram and simple structural schematic of the newly postulated auxin responsive transcriptional regulatory complex(A) Domain diagrams of a typical Aux/IAA repressor family protein and a typical Auxin Response Factor (ARF) transcription factor. (B) A highly simplified structural schematic of an ARF regulatory complex in the absence of auxin. An ARF dimer is bound to an Auxin Response Element (AuxRE) inverted repeat. ARF and Aux/IAA PB1 domains form multimers, interacting via positive and negative faces. Structural data exist for domains with solid colors and lines, whereas dashed lines represent domains of unknown structure.DBD, DNA-binding domain, DD, dimerization domain; B3, B3 DNA-binding domain; AD, ancillary domain; MR, middle region; PB1, PB1 protein-protein interaction domain; EAR, EAR motif corepressor-binding domain; Deg, degron motif; N, N-terminus; C, C-terminus.
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fig-001: Domain diagram and simple structural schematic of the newly postulated auxin responsive transcriptional regulatory complex(A) Domain diagrams of a typical Aux/IAA repressor family protein and a typical Auxin Response Factor (ARF) transcription factor. (B) A highly simplified structural schematic of an ARF regulatory complex in the absence of auxin. An ARF dimer is bound to an Auxin Response Element (AuxRE) inverted repeat. ARF and Aux/IAA PB1 domains form multimers, interacting via positive and negative faces. Structural data exist for domains with solid colors and lines, whereas dashed lines represent domains of unknown structure.DBD, DNA-binding domain, DD, dimerization domain; B3, B3 DNA-binding domain; AD, ancillary domain; MR, middle region; PB1, PB1 protein-protein interaction domain; EAR, EAR motif corepressor-binding domain; Deg, degron motif; N, N-terminus; C, C-terminus.

Mentions: The forward nuclear auxin signaling pathway can be reconstituted in yeast using only five plant parts [28], providing strong evidence that this circuit represents the minimal auxin-specific response machinery. These parts include ARFs, which are able to bind to promoters containing AuxREs [6,7]. In the absence of auxin, ARFs are bound to Aux/IAA repressor proteins (Figure 1B) [8]. Repression by Aux/IAAs is facilitated by recruitment of TOPLESS-type corepressors (TPLs) [29]. Auxin relieves ARFs of this repression by enhancing associations between Aux/IAAs and members of the TIR1/AFB family of auxin receptors [12]. TIR1/AFBs act as the substrate recognition subunit of Skp1-Cullin-F-box E3 ubiquitin-ligase complexes. Thus, auxin promotes ubiquitination and subsequent degradation of Aux/IAAs, relieving transcriptional repression on auxin response genes [13,14]. The mechanism by which ARFs mediate transcriptional activation is not well understood.


New tangles in the auxin signaling web.

Wright RC, Nemhauser JL - F1000Prime Rep (2015)

Domain diagram and simple structural schematic of the newly postulated auxin responsive transcriptional regulatory complex(A) Domain diagrams of a typical Aux/IAA repressor family protein and a typical Auxin Response Factor (ARF) transcription factor. (B) A highly simplified structural schematic of an ARF regulatory complex in the absence of auxin. An ARF dimer is bound to an Auxin Response Element (AuxRE) inverted repeat. ARF and Aux/IAA PB1 domains form multimers, interacting via positive and negative faces. Structural data exist for domains with solid colors and lines, whereas dashed lines represent domains of unknown structure.DBD, DNA-binding domain, DD, dimerization domain; B3, B3 DNA-binding domain; AD, ancillary domain; MR, middle region; PB1, PB1 protein-protein interaction domain; EAR, EAR motif corepressor-binding domain; Deg, degron motif; N, N-terminus; C, C-terminus.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4335792&req=5

fig-001: Domain diagram and simple structural schematic of the newly postulated auxin responsive transcriptional regulatory complex(A) Domain diagrams of a typical Aux/IAA repressor family protein and a typical Auxin Response Factor (ARF) transcription factor. (B) A highly simplified structural schematic of an ARF regulatory complex in the absence of auxin. An ARF dimer is bound to an Auxin Response Element (AuxRE) inverted repeat. ARF and Aux/IAA PB1 domains form multimers, interacting via positive and negative faces. Structural data exist for domains with solid colors and lines, whereas dashed lines represent domains of unknown structure.DBD, DNA-binding domain, DD, dimerization domain; B3, B3 DNA-binding domain; AD, ancillary domain; MR, middle region; PB1, PB1 protein-protein interaction domain; EAR, EAR motif corepressor-binding domain; Deg, degron motif; N, N-terminus; C, C-terminus.
Mentions: The forward nuclear auxin signaling pathway can be reconstituted in yeast using only five plant parts [28], providing strong evidence that this circuit represents the minimal auxin-specific response machinery. These parts include ARFs, which are able to bind to promoters containing AuxREs [6,7]. In the absence of auxin, ARFs are bound to Aux/IAA repressor proteins (Figure 1B) [8]. Repression by Aux/IAAs is facilitated by recruitment of TOPLESS-type corepressors (TPLs) [29]. Auxin relieves ARFs of this repression by enhancing associations between Aux/IAAs and members of the TIR1/AFB family of auxin receptors [12]. TIR1/AFBs act as the substrate recognition subunit of Skp1-Cullin-F-box E3 ubiquitin-ligase complexes. Thus, auxin promotes ubiquitination and subsequent degradation of Aux/IAAs, relieving transcriptional repression on auxin response genes [13,14]. The mechanism by which ARFs mediate transcriptional activation is not well understood.

Bottom Line: This potential combinatorial diversity in signaling pathways likely contributes to the myriad of context-specific responses to auxin.Recent structures of several domains from ARF proteins have exposed new modes of ARF dimerization, new models for ARF-AuxRE specificity, and the strong likelihood of larger order complexes formed by ARF and Aux/IAA homo- and heteromultimerization.Preliminary experiments support a role for these novel interactions in planta, further increasing the potential architectural complexity of this seemingly simple pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, University of Washington, Seattle Washington 98195 USA.

ABSTRACT
Plants use auxin to relay critical information that shapes their growth and development. Auxin perception and transcriptional activation are mediated by the degradation of Aux/IAA repressor proteins. Degradation of Aux/IAAs relieves repression on Auxin Response Factors (ARFs), which bind DNA sequences called Auxin Response Elements (AuxREs). In most higher plant genomes, multiple paralogs exist for each part of the auxin nuclear signaling pathway. This potential combinatorial diversity in signaling pathways likely contributes to the myriad of context-specific responses to auxin. Recent structures of several domains from ARF proteins have exposed new modes of ARF dimerization, new models for ARF-AuxRE specificity, and the strong likelihood of larger order complexes formed by ARF and Aux/IAA homo- and heteromultimerization. Preliminary experiments support a role for these novel interactions in planta, further increasing the potential architectural complexity of this seemingly simple pathway.

No MeSH data available.


Related in: MedlinePlus