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Gene Review

IAA1  -  auxin-responsive protein IAA1

Arabidopsis thaliana

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Disease relevance of IAA1


High impact information on IAA1

  • Expression studies using an auxin-regulated reporter suggest that AUX1 is necessary for root gravitropism by facilitating basipetal auxin transport to distal elongation zone tissues [2].
  • The tir1 mutants are deficient in a variety of auxin-regulated growth processes including hypocotyl elongation and lateral root formation [3].
  • The identification of IAMT1 and the elucidation of its role in Arabidopsis leaf development have broad implications for auxin-regulated developmental process [4].
  • In particular, a clear reduction in endogenous levels of free indoleacetic acid (IAA) and IAA conjugates was shown [5].
  • The stunted growth of the mutant is not rescued by gibberellin, brassinosteroid, or indoleacetic acid application and is not attributable to excessive ethylene response, but supplementing the medium with Glc improves viability and root growth [6].

Biological context of IAA1


Anatomical context of IAA1

  • In a transient assay system in tobacco protoplasts using steady-state differences as an indirect measure of protein half-life, LUC fusions with full-length PSIAA6 and IAA1, an Aux/IAA protein from Arabidopsis, resulted in protein accumulations that were 3.5 and 1 [11].

Associations of IAA1 with chemical compounds

  • The molecular cloning of AXR5 revealed that the gene encodes the IAA1 protein, a member of the Aux/IAA family of proteins [8].
  • We used a steroid hormone-inducible system to reveal putative roles and downstream signaling of IAA1 in auxin response [12].
  • The response of most family members to IAA is rapid (within 4 to 30 minutes) and insensitive to cycloheximide [13].
  • The B3 DNA binding domain is shared amongst various plant-specific transcription factors, including factors involved in auxin-regulated and abscisic acid-regulated transcription [14].
  • Local application of the auxin-transport inhibitor naphthylphthalamic acid (NPA) at the root-shoot junction decreased the number and density of lateral roots and reduced the free indoleacetic acid (IAA) levels in the root and [3H]IAA transport into the root [15].

Physical interactions of IAA1

  • Biochemical studies show that IAA1/AXR5 interacts with TIR1 in an auxin-dependent manner [8].

Regulatory relationships of IAA1


Other interactions of IAA1


Analytical, diagnostic and therapeutic context of IAA1

  • For example, the expression of several genes, such as those encoding members of LATERAL ORGAN BOUNDARIES domain proteins and AUXIN-REGULATED GENE INVOLVED IN ORGAN SIZE, are disrupted in the double mutant [19].
  • GUS expression was preferentially enhanced in the root elongation zone after treatment of young seedlings with 10(-7) M IAA [20].
  • The genes were structurally characterized and sequence analysis of their 5'-flanking regions revealed the presence of several highly conserved sequences found in various auxin-regulated genes from other plant species [21].


  1. ACS4, a primary indoleacetic acid-responsive gene encoding 1-aminocyclopropane-1-carboxylate synthase in Arabidopsis thaliana. Structural characterization, expression in Escherichia coli, and expression characteristics in response to auxin [corrected]. Abel, S., Nguyen, M.D., Chow, W., Theologis, A. J. Biol. Chem. (1995) [Pubmed]
  2. Localization of the auxin permease AUX1 suggests two functionally distinct hormone transport pathways operate in the Arabidopsis root apex. Swarup, R., Friml, J., Marchant, A., Ljung, K., Sandberg, G., Palme, K., Bennett, M. Genes Dev. (2001) [Pubmed]
  3. The TIR1 protein of Arabidopsis functions in auxin response and is related to human SKP2 and yeast grr1p. Ruegger, M., Dewey, E., Gray, W.M., Hobbie, L., Turner, J., Estelle, M. Genes Dev. (1998) [Pubmed]
  4. An indole-3-acetic acid carboxyl methyltransferase regulates Arabidopsis leaf development. Qin, G., Gu, H., Zhao, Y., Ma, Z., Shi, G., Yang, Y., Pichersky, E., Chen, H., Liu, M., Chen, Z., Qu, L.J. Plant Cell (2005) [Pubmed]
  5. Auxin and light control of adventitious rooting in Arabidopsis require ARGONAUTE1. Sorin, C., Bussell, J.D., Camus, I., Ljung, K., Kowalczyk, M., Geiss, G., McKhann, H., Garcion, C., Vaucheret, H., Sandberg, G., Bellini, C. Plant Cell (2005) [Pubmed]
  6. The Arabidopsis thaliana ABSCISIC ACID-INSENSITIVE8 encodes a novel protein mediating abscisic acid and sugar responses essential for growth. Brocard-Gifford, I., Lynch, T.J., Garcia, M.E., Malhotra, B., Finkelstein, R.R. Plant Cell (2004) [Pubmed]
  7. Protein-protein interactions among the Aux/IAA proteins. Kim, J., Harter, K., Theologis, A. Proc. Natl. Acad. Sci. U.S.A. (1997) [Pubmed]
  8. The IAA1 protein is encoded by AXR5 and is a substrate of SCF(TIR1). Yang, X., Lee, S., So, J.H., Dharmasiri, S., Dharmasiri, N., Ge, L., Jensen, C., Hangarter, R., Hobbie, L., Estelle, M. Plant J. (2004) [Pubmed]
  9. The indolic compound hypaphorine produced by ectomycorrhizal fungus interferes with auxin action and evokes early responses in nonhost Arabidopsis thaliana. Reboutier, D., Bianchi, M., Brault, M., Roux, C., Dauphin, A., Rona, J.P., Legué, V., Lapeyrie, F., Bouteau, F. Mol. Plant Microbe Interact. (2002) [Pubmed]
  10. Yokonolide B, a novel inhibitor of auxin action, blocks degradation of AUX/IAA factors. Hayashi, K., Jones, A.M., Ogino, K., Yamazoe, A., Oono, Y., Inoguchi, M., Kondo, H., Nozaki, H. J. Biol. Chem. (2003) [Pubmed]
  11. Degradation of Aux/IAA proteins is essential for normal auxin signalling. Worley, C.K., Zenser, N., Ramos, J., Rouse, D., Leyser, O., Theologis, A., Callis, J. Plant J. (2000) [Pubmed]
  12. Mutation in domain II of IAA1 confers diverse auxin-related phenotypes and represses auxin-activated expression of Aux/IAA genes in steroid regulator-inducible system. Park, J.Y., Kim, H.J., Kim, J. Plant J. (2002) [Pubmed]
  13. The PS-IAA4/5-like family of early auxin-inducible mRNAs in Arabidopsis thaliana. Abel, S., Nguyen, M.D., Theologis, A. J. Mol. Biol. (1995) [Pubmed]
  14. Solution structure of the B3 DNA binding domain of the Arabidopsis cold-responsive transcription factor RAV1. Yamasaki, K., Kigawa, T., Inoue, M., Tateno, M., Yamasaki, T., Yabuki, T., Aoki, M., Seki, E., Matsuda, T., Tomo, Y., Hayami, N., Terada, T., Shirouzu, M., Osanai, T., Tanaka, A., Seki, M., Shinozaki, K., Yokoyama, S. Plant Cell (2004) [Pubmed]
  15. Inhibition of auxin movement from the shoot into the root inhibits lateral root development in Arabidopsis. Reed, R.C., Brady, S.R., Muday, G.K. Plant Physiol. (1998) [Pubmed]
  16. Arabidopsis SHY2/IAA3 inhibits auxin-regulated gene expression. Tian, Q., Uhlir, N.J., Reed, J.W. Plant Cell (2002) [Pubmed]
  17. The F-box protein TIR1 is an auxin receptor. Dharmasiri, N., Dharmasiri, S., Estelle, M. Nature (2005) [Pubmed]
  18. AXR1-ECR1-dependent conjugation of RUB1 to the Arabidopsis Cullin AtCUL1 is required for auxin response. del Pozo, J.C., Dharmasiri, S., Hellmann, H., Walker, L., Gray, W.M., Estelle, M. Plant Cell (2002) [Pubmed]
  19. Functional genomic analysis of the AUXIN RESPONSE FACTOR gene family members in Arabidopsis thaliana: unique and overlapping functions of ARF7 and ARF19. Okushima, Y., Overvoorde, P.J., Arima, K., Alonso, J.M., Chan, A., Chang, C., Ecker, J.R., Hughes, B., Lui, A., Nguyen, D., Onodera, C., Quach, H., Smith, A., Yu, G., Theologis, A. Plant Cell (2005) [Pubmed]
  20. age Mutants of Arabidopsis exhibit altered auxin-regulated gene expression. Oono, Y., Chen, Q.G., Overvoorde, P.J., Köhler, C., Theologis, A. Plant Cell (1998) [Pubmed]
  21. Structural characterization of the early indoleacetic acid-inducible genes, PS-IAA4/5 and PS-IAA6, of pea (Pisum sativum L.). Oeller, P.W., Keller, J.A., Parks, J.E., Silbert, J.E., Theologis, A. J. Mol. Biol. (1993) [Pubmed]
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