Seminars

Auxin regulates a bewildering array of processes during plant growth and development. This complexity contrasts with the apparent simplicity of the auxin-signaling pathway.  Auxin regulates transcription through the TIR1/AFB-Aux/IAA-ARF pathway. The hormone directly binds to the F-box protein of the SCFTIR1/AFB ubiquitin protein ligase E3 and promotes an
interaction with the Aux/IAA transcriptional repressors, thus stimulating their degradation. Loss of the Aux/IAAs permits ARF-dependent transcription.
In the case of the TIR1/AFB proteins, recent results indicate that different members of the family have distinct activities both with respect to auxin binding and Aux/IAA interaction. We are currently exploring the possibility that these differences contribute to the complexity of auxin response.  We
are also investigating the downstream transcriptional networks that mediate auxin-dependent growth responses.  Finally, we are using the bryophyte Physcomitrella patens to identify ancestral components of auxin signaling pathways. Our results indicate that the mechanism of auxin signaling is conserved in land plants.