Characterization of AFB5 in Arabidopsis Auxin Signaling




Minter, Lauren

Journal Title

Journal ISSN

Volume Title



Auxin is a pivotal hormone that regulates nearly every aspect of plant growth and development, both genomic as well as non-genomic responses. Genomic responses are regulated through the degradation of a group of transcriptional repressors called Aux/IAA proteins. These repressors are degraded through the ubiquitin-proteasome pathway involving SCF TIR1/AFBs in which TIR1/AFBs function as auxin co-receptors. TIR1 gene family in Arabidopsis consists of 6 genes, of which AFB4 and AFB5 are distantly related to TIR1. Two mutant alleles of Arabidopsis AFB5 (pic3 and pic59) were isolated through a genetic screen for picloram resistance, a synthetic auxin commonly used as an herbicide. Both mutant alleles exhibit primary root growth resistance to picloram and indole-3-butyric acid (IBA), but not to indole-3-acetic acid (IAA) and results indicate that AFB5 may not promote Aux/IAA degradation, suggesting that it functions partially or completely differently from TIR1. afb5 resistance to IBA in primary root elongation, lateral root proliferation, as well as altered responses to IBA-induced gene expression raises the possibility that AFB5 is involved in IBA rather than IAA signaling, however the role of IBA in auxin signaling still remains unclear. pic3 and pic59 display altered lateral root densities and primary root elongation, and expression of cell division reporter CyclinB



AFB5, Auxin signaling


Minter, L. (2015). Characterization of AFB5 in Arabidopsis auxin signaling (Unpublished thesis). Texas State University, San Marcos, Texas.


Rights Holder

Rights License

Rights URI