Disease relevance of auxin

• After decapitation and treatment of epicotyls with IAA, synthetases also appear in a smooth vesicle fraction (density 1.11 g/cm3) which is rich in endoplasmic reticulum (ER) marker enzyme [1].
• Exposure to newly synthesised analogues of IAA shows a range of four orders of magnitude difference in cellular toxicity but no structure-activity relationships are apparent, in contrast to well-defined redox dependencies of oxidation by HRP intermediates or rates of decarboxylation of radical-cation intermediates [2].
• Resistance of transgenic tobacco seedlings expressing the Agrobacterium tumefaciens C58-6b gene, to growth-inhibitory levels of cytokinin is associated with elevated IAA levels and activation of phenylpropanoid metabolism [3].
• Effect of beta-indoleacetic acid on RNA and protein synthesis in Escherichia coli [4].

High impact information on auxin

• Six other Arabidopsis genes were specifically active on indole-3-acetic acid (IAA), and one was active on both IAA and salicylic acid [5].
• The highly pure (ca. 95%) plasma membrane vesicles maintained a pH differential across the membrane and accumulated a tritiated azido analogue of 3-indoleacetic acid (IAA), 5-azido-[7-3H]IAA ([3H]N3IAA), in a manner similar to the accumulation of [3H]IAA [6].
• The results of equilibrium dialysis experiments on the binding of beta-indoleacetic acid were consistent with the presence of a single weak binding site per subunit of protein, having an association constant of about 7 X 10(2) M-1 [7].
• The molecular cloning of AXR5 revealed that the gene encodes the IAA1 protein, a member of the Aux/IAA family of proteins [8].
• Exogenous indole-3-acetic acid (IAA) enhances the constitutive expression of ACS2, 4, 5, 6, 7, 8, and 11 in the root [9].

Chemical compound and disease context of auxin

• Substituted indole-3-acetic acid (IAA) derivatives, plant auxins with potential for use as prodrugs in enzyme-prodrug directed cancer therapies, were oxidised with horseradish peroxidase (HRP) and toxicity against V79 Chinese hamster lung fibroblasts was determined [10].
• Hairy roots of interspecific hybrid ginseng (Panax ginseng x P. quinquefolium), induced by Agrobacterium rhizogenes ATCC 15834, grew well in B5 liquid media supplemented with 2.5 microM auxins (3-indole butyric acid (IBA), 1-naphtaleneacetic acid (NAA) and 3-indoleacetic acid (IAA)) [11].

Biological context of auxin

• Similar analysis with root tip tissue treated with IAA reveals unique and overlapping expression patterns in the various cell types of the lateral root cap, cell division, and cell expansion zones [9].
• The thiamin diphosphate (ThDP)-dependent enzyme indolepyruvate decarboxylase (IPDC) is involved in the biosynthetic pathway of the phytohormone 3-indoleacetic acid and catalyzes the nonoxidative decarboxylation of 3-indolepyruvate to 3-indoleacetaldehyde and carbon dioxide [12].
• IAA is tolerated by humans in high doses and HRP is a robust enzyme meeting many of the requirements for targeting to tumours by coupling to antibodies or polymers, or by gene transfection [13].
• Upon treatment with IAA/HRP, liposomes undergo lipid peroxidation, strand breaks and adducts are formed in supercoiled plasmid DNA, and mammalian cells in culture lose colony-forming ability [2].
• The phenotype of MjCM-1 expressed at low levels can be rescued by the addition of indole-3-acetic acid (IAA), indicating MjCM-1 overexpression reduces IAA biosynthesis [14].

Anatomical context of auxin

• Here a novel model for IAA signaling pathway mediated by extracellular ROS produced by cell-wall POXs is proposed [15].
• The elimination of nicardipine in liver microsomes was decreased significantly in the presence of 3-indoxylsulfate and 3-indoleacetic acid [16].
• The effect of different concentrations of beta-indoleacetic acid (IAA) on RNA and protein synthesis and the stability of associations of E. coli ribosomes at 3 mM Mg2+ was investigated [4].

Associations of auxin with other chemical compounds

• Further, while rat serum albumin strongly bound L-tryptophan and indolyl-3-acetic acid (Ka approximately equal to 10(5) M-1), rat alpha 1-fetoprotein did not bind any of the indoles tested [17].
• After seven days of culture of White Sim petals, NAA may account for the changes found in the levels of IAA and DHZR, whereas TDZ may be responsible for the remarkable increases in N6-(delta2-isopentenyl)adenine (iP) and ZR [18].
• Serotonin, TRP, and IAA results were verified by cross-validation with an external laboratory using a previously validated HPLC method with fluorometric detection [19].
• The Rhus root culture showed the highest productivity for those secondary metabolites in a modified Linsmaier-Skoog (LS) liquid medium containing 30 mM NH4+ and 30 mM NO3- as nitrogen sources in the presence of 10(-6) M 3-indoleacetic acid (IAA) [20].
• This study reports the effects of thidiazuron (TDZ) on the endogenous levels of indoleacetic acid (IAA), zeatin, zeatin riboside ([9R]Z), isopentenyladenine and isopentenyladenosine ([9R]iP) as well as structural changes in the apical meristem of Dendrobium Second Love shoots during flower induction and initial development in vitro [21].
• A significant increase in the number of lateral roots under the Pi- Suc- condition in the chalcone synthase mutant (tt4-2) indicated a potential role for flavonoids in auxin-mediated Pi deficiency-induced modulation of RSA [22].
• Plants overaccumulating the defense signal molecule salicylic acid (SA) frequently display morphological phenotypes that are reminiscent of auxin-deficient or auxin-insensitive mutants, indicating that SA might interfere with auxin responses [23].
• The results indicate that auxin relies on NO in inducing PA, phosphatidylinositol phosphate, and phosphatidylinositol bisphosphate accumulation [24].

Gene context of auxin

• TIR1 is part of a ubiquitin protein ligase required for degradation of Aux/IAA proteins [8].
• An amplified auxin asymmetry may explain the mdr4 hypertropism [25].
• These results indicate that the increased auxin efflux activity conferred by PGP4 reduces auxin levels in the root hair cell and consequently inhibits root hair elongation [26].
• Modulation of auxin sensitivity by Pi was found to depend on the auxin receptor TRANSPORT INHIBITOR RESPONSE1 (TIR1) and the transcription factor AUXIN RESPONSE FACTOR19 (ARF19) [27].
• The efficacy of a number of auxin analogues and auxin transport inhibitors to displace IAA binding from AUX1 has also been determined and can be rationalized in terms of their physiological effects [28].
• Taken together, our data show that D6PK is required for efficient auxin transport and suggest that PIN proteins are D6PK phosphorylation targets [29].
• Our results are consistent with the possibility that limiting accumulation of the IAA precursor IBA via PDR8-promoted efflux contributes to auxin homeostasis [30].
• Immunolocalization of the PINFORMED1 (PIN1) polar auxin transporter revealed that PIN1 expression marks leaf primordia in maize, similarly to Arabidopsis [31].
• We show that auxin promoted PIN2 recycling from endosomes to the PM and increased PIN2 steady state levels in the PM fraction [32].
• We therefore suggest that the auxin phenotypes of iar4 mutants are the result of altered IAA homeostasis [33].
• This involves repression of the AUXIN INDUCIBLE (Aux/IAA) gene AXR2/IAA7, encoding a key component of ABA- and auxin-dependent responses during postgerminative growth [34].

Analytical, diagnostic and therapeutic context of auxin

• IAA, a weakly bound ligand, was rapidly excreted by the transplanted kidney during the first one to three days after renal transplantation, but CMPF, a strongly bound ligand, was slowly excreted [35].
• A rapid, highly efficient trapping system for the collection of 3-indoleacetic acid from a gas chromatography column [36].
• Transported radioactivity recovered from agar blocks eluted at the same retention time as authentic [3H]-IAA during HPLC fractionation [37].
• A new enzyme immunoassay micromethod for differential quantitation of the main natural forms of indolyl 3-acetic acid [38].
• Distribution of scopolamine and IAA was then determined by enzyme-linked immunosorbent assay (ELISA) [39].

References