Table of Contents
Auxin signaling pathway is regulated by the Ubiquitin 26S proteolysis system. The signaling pathway is discussed in this section. It is important for any kinds of Life Science related competitive exams.
Receptor of Auxin:
TIR1 (Transport Inhibitor Response 1)/ AFB1-5
TIR1:
TIR1 is a F-Box protein. It acts as a component of the SCF, a E3 ubiquitin ligase that transfer ubiquitin molecule to the Aux/IAA proteins, targeting them for proteolysis by the 26S proteosome.
Another receptor:
Auxin also acts through its interaction with another receptor protein-ABP1 (Auxin binding protein-1). It is located in the lumen of endoplasmic reticulum as well as plasma membrane.
Inhibitor of Auxin signaling pathway:
Aux/IAA proteins.
Ligand:
Auxin
Signaling pathway:
Ubiquitin 26S proteolysis system.
The description of the auxin signaling pathway:
Auxin binds to TIR1. It mediates physiological effects through the transcriptional regulation. When TIR1 binds auxin, the complex then binds to Aux/IAA proteins.
A] In the absence of auxin:
Aux/IAAs directly interact with ARFs (Auxin Response Factor- a transcription factor) and prevent their transcriptional activity.
B] In the presence of auxin:
AUX/IAAs are rapidly eliminated abrogating their inhibition of ARFs and the expressions of Auxin responses genes.
The auxin receptor, TIR1 acts as a component of the SCF, a E3 ubiquitin ligase that transfer ubiquitin molecule to the Aux/IAA proteins, targeting them for proteolysis by the 26S proteosome.
In this way, auxin triggers the binding of Aux/IAA- TIR1 binding and ubiquitination and degradation of Aux/IAAs.
But, how the TIR1 protein senses and becomes activated by auxin remains unknown.
Result:
Plant growth and development.
Other related notes:
- Auxin biosynthesis: https://thebiologyislove.com/auxin-biosynthesis-pathway-2-types/
- Gibberellin signaling pathway: https://thebiologyislove.com/ga1-gibberellin-signaling-pathway/
- Cytokinin signaling pathway: https://thebiologyislove.com/cytokinin-signaling-pathway/
- Ethylene signaling pathway: https://thebiologyislove.com/ethylene-signaling-pathway/
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