TOBFAC: The database of tobacco transcription factors
Family: AUX-IAA
Minimum number of tobacco AUX-IAA genes: 35
Count of tobacco AUX-IAA sequences: 52
Pfam accession: AUX_IAA
SHOULD possess AUX_IAA domain but SHOULD NOT possess Auxin_resp domain
The Aux/IAA family of genes are key regulators of auxin-modified gene expression. The plant hormone auxin (indole-3-acetic acid, IAA) regulates diverse cellular and developmental responses in plants, including cell division, expansion, differentiation and patterning of embryo responses. Auxin can regulate the gene expression of several families, including GH3 and SAUR, as well as Aux/IAA itself. The Aux/IAA proteins act as repressors of auxin-induced gene expression, possibly through modulating the activity of DNA-binding auxin response factors (ARFs). Aux/IAA and ARF are thought to interact through C-terminal protein-protein interaction domains found in both Aux/IAA and ARF.
Recent evidence suggests that Aux/IAA proteins can also mediate light responses. Some members of the AUX/IAA family are longer and contain an N-terminal DNA binding domain and may have an early function in the establishment of vascular and body patterns in embryonic and post-embryonic development in some plants.
Aux/IAA proteins are short-lived nuclear proteins that repress expression of primary/early auxin response genes in protoplast transfection assays. Repression is thought to result from Aux/IAA proteins dimerizing with auxin response factor (ARF) transcriptional activators that reside on auxin-responsive promoter elements, referred to as AuxREs. Most Aux/IAA proteins contain four conserved domains, designated domains I, II, III, and IV. Domain II and domains III and IV play roles in protein stability and dimerization, respectively. A clear function for domain I had not been established. Results reported here indicate that domain I in Aux/IAA proteins is an active repression domain that is transferable and dominant over activation domains. An LxLxL motif within domain I is important for conferring repression. The dominance of Aux/IAA repression domains over activation domains in ARF transcriptional activators provides a plausible explanation for the repression of auxin response genes via ARF-Aux/IAA dimerization on auxin-responsive promoters.
Liscum, E; Reed, JW. Genetics of Aux/IAA and ARF action in plant growth and development. Plant Mol. Biol. 2002. 49(3-4):387-400 PMID: 12036262
Tiwari, SB; Hagen, G; Guilfoyle, TJ. Aux/IAA proteins contain a potent transcriptional repression domain. Plant Cell 2004. 16(2):533-43 PMID: 14742873
Tiwari, SB; Wang, XJ; Hagen, G; Guilfoyle, TJ. AUX/IAA proteins are active repressors, and their stability and activity are modulated by auxin. Plant Cell 2001.13(12):2809-22 PMID: 11752389
Reed JW. Roles and activities of Aux/IAA proteins in Arabidopsis. Trends Plant Sci. 2001 Sep;6(9):420-5. PMID: 11544131
Number of contigs: 36
Number of singlets: 16
Number of N terminal – 17
Number of C terminal – 25
Number of full – 10
Total minimum number – 35
| Family | Genbank ID | Name |
| AUX-IAA | AF123505 | Nt-iaa2.5 deduced protein |
Paul J Rushton
Marta T. Bokowiec
Xianfeng (Jeff) Chen
Thomas (Tom) W Laudeman
Jennifer F. Brannock
Michael P. Timko