Auxin initiate complex growth and development processes in plants through its signalling pathway. The mechanism of action of this hormone facilitate the rapid or spontaneous switching between transcriptional repression and gene activation via the auxin-dependent degradation of transcriptional repressor.
The signalling pathway consists of small number of core proteins or protein components which are represented by large gene family. This core proteins belongs to 3 protein family.
F-box Transport Inhibitor Response 1/ Auxin Signalling F-box protein (TIR1/AFB)Auxin/ Indole-3-Acetic Acid (AUX/IAA)transcriptional repressorAuxin Response For (ARF) transcription factors.
The hormone auxin facilitate the interaction of TIR/AFB and AUX/IAA. Hence leading to the release of ARF repression. Gene expression associated with ARF activation have been implicated in diverse processes in land plants, Including embryogenesis, establishment of polarity and tropic responses.
￼At low concentrations of auxin levels, AUX/IAA transcriptional repressor interact with ARF and repress their activity. When TIR1/AFB proteins bind to AUX/IAA transcriptional repressor which mediates the subsequent poly ubiquitylation and subsequent proteasomal degradation. Rapid induction of auxin responsive genes including a us AUX/IAA, GH3 negative feedback loops. AUX/IAAtranscriptional repressor interact with proteins in the signallin pathway through three different domains leucine repeat EAR motif within domain 1Internal domain II which contains a GWP-core degron motifC- terminal region