Disease relevance of IAA1

• 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] [1].

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

• Screening an Arabidopsis lambda-ACT cDNA library using IAA1 as a bait reveals heterotypic interactions of IAA1 with known and newly discovered members of the Arabidopsis Aux/IAA gene family [7].
• The mutation prevents this interaction suggesting that the mutant phenotype is caused by the accumulation of IAA1/AXR5 [8].
• Combinatorial interactions among the various members of the Aux/IAA gene family may regulate a variety of late genes as well as serve as autoregulators of early auxin-regulated gene expression [7].
• In addition, we show that hypaphorine counteracts the rapid upregulation by indole-3-acetic acid and 1-naphthalenic-acetic acid of the primary auxin-responsive gene IAA1 and induces a rapid, transient membrane depolarization in root hairs and suspension cells, due to the modulation of anion and K+ currents [9].
• YkB blocks auxin-dependent cell division and auxin-regulated epinastic growth mediated by auxin-binding protein 1 [10].

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

• Arabidopsis SHY2/IAA3 inhibits auxin-regulated gene expression [16].
• In etiolated seedlings, ACS4 is specifically induced by indoleacetic acid (IAA) [1].

Other interactions of IAA1

• Here, we show that the pea PS-IAA4 and Arabidopsis IAA1 and IAA2 proteins perform homo- and heterotypic interactions in yeast using the two-hybrid system [7].
• Gel-filtration chromatography and chemical cross-linking experiments demonstrate that the PS-IAA4 and IAA1 proteins interact to form homodimers in vitro [7].
• Gain-of-function mutations in SHY2/IAA3 cause enlarged cotyledons, short hypocotyls, and altered auxin-regulated root development [16].
• Together, these results indicate that TIR1 is an auxin receptor that mediates Aux/IAA degradation and auxin-regulated transcription [17].
• Mutations in the AXR1 gene result in a reduction in auxin response and diverse defects in auxin-regulated growth and development [18].

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].

References