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At least 73 records · Page 4Linked to original sources
PubMed1968

Influence of Substrate and Tissue Manganese on the IAA-Oxidase System in Cotton.

Tissue manganese was found to influence the indoleacetic acid (IAA) system of cotton over a wide range of concentrations. The cofactor and inhibitor activities of the IAA-oxidase system were affected as the concentration of manganese in the tissue was varied. Maximum inhibitor activity was found in leaf extracts from the plants grown in 0.5 mg/l manganese (Hoagland's level). The inhibitor activity decreased in the leaf extracts of plants grown at concentrations of manganese either higher or lower than 0.5 mg/l. Abnormally high IAA-oxidase activity was found in the leaves of plants grown in deficient levels of manganese (<0.0005, 0.005 mg/l) and the extracts from plants in the <0.0005 mg/l Mn treatment showed IAA-oxidase cofactor activity.

Journal Article↗
PubMed1969

Flower Formation in Excised Tobacco Stem Segments; II. Reversible Removal of IAA Inhibition by RNA Base Analogues.

The RNA base analogues, 2-thiouracil, 6-azauracil and 8-azaguanine incorporated singly into the medium, increased the number of floral buds in excised stem segments of Nicotiana tabacum variety Wisconsin No. 38 cultured in vitro. Combined treatments with 2 and 3 base analogues were even more effective. The effects were prevented by the corresponding natural counterparts, uracil, uridine, and guanosine respectively. These nucleic acid constituents added to cultures without base analogues did not affect the number of floral buds formed. In stem segments from the lower internodes treatments with the analogues effected a transition from vegetative to floral bud formation, thus in a sense removing the floral gradient as defined by Chouard and Aghion.The inhibition of flower bud formation ordinarily achieved even with low concentrations of indole-3-acetic acid (IAA) was counteracted by low concentrations of 2-thiouracil, 6-azauracil and 8-azaguanine. Reversal to vegetative bud formation was not achieved even with high IAA concentrations in the presence of the base analogues.Stem segments excised from young, vegetative tobacco plants never formed floral buds in vitro. Thus, the inhibiting effect of IAA and the promoting effect of base analogues seem to be on the expression and not on the induction of flowering. The regulatory action of the IAA and base analogues in flower bud formation is tentatively ascribed to their differential effects on RNA synthesis.

Journal Article↗
PubMed1987

Effect of pH on IAA Uptake by Maize Root Segments.

The uptake of [5-(3)H]indoleacetic acid (IAA) by Zea mays L. root segments involves nonsaturable and saturable processes. The pH optimum of the saturable component was found to be 5.0. The proton ionophore carbonylcyanide p-trifluoromethoxyphenylhydrazone inhibited at 100 micromolar the saturable component of IAA uptake but had no effect on non-saturable uptake. This indicates that the saturable component of IAA uptake is dependent on the proton gradient across the plasmalemma. The high level of proton extrusion in the elongation zone of the root will stimulate nonsaturable and saturable uptake of IAA in that zone.

Journal Article↗
PubMed2000

IAA-synthase, an enzyme complex from Arabidopsis thaliana catalyzing the formation of indole-3-acetic acid from (S)-tryptophan.

An enzyme complex was isolated from Arabidopsis thaliana that catalyzes the entire pathway of biosynthesis of the major plant growth hormone, indole-3-acetic acid (IAA), from (S)-tryptophan. The 160-180 kDa, soluble complex catalyzes a strictly O2-dependent reaction which requires no further added factors and is stereospecific for the substrate (S)-tryptophan (app. Km = 120 microM). H2(18)O labeling proved that both oxygen atoms of IAA were delivered via H2O. This, as well as immunological evidence for the presence of a nitrilase-like protein in the complex, suggests the reaction to proceed via the intermediate indole-3-acetonitrile. IAA-synthase forms a tight metabolite channel committed to IAA production and occurs in shoots, roots and cell cultures of A. thaliana.

Arabidopsis↗
PubMed2006

Kinetics of inactivation of phytase (phy A) during modification of histidine residue by IAA and DEP.

Chemical probing of histidine residues using specific modifiers, iodoacetic acid (IAA) and diethylpyrocarbonate (DEP) resulted in the inactivation of phytase (phy A). The kinetic theory of the substrate reaction during the modification of enzyme activity was applied to a study of the kinetics of the course of inactivation of phytase by IAA and DEP. The results suggested that histidine residues are involved in the active site of the enzyme. They also indicated that inactivation of the enzyme by IAA was via a complexing type inhibition, while the inhibition by DEP reaction involved a conformational change step before inactivation. The dissociation constant of the enzyme-inhibitor complex of IAA, the constant of the conformational change of DEP and the microscopic rate constants of two inhibitors were obtained.

6-Phytase↗
PubMed2000

Time clustering of high titre insulin autoantibodies (IAA) in the cord blood of infants born to non-diabetic mothers.

Insulin autoantibodies (IAA) are markers for autoimmune insulitis, and are reported in up to 100% of diabetic children before the age of five years, but in fewer than 1% of their controls. Their origins are unknown. In this report a cluster of high titre IAA in cord blood is reported, distinct from the low titre 'non-specific' binding previously described. The distributions of displaceable insulin binding measured in adults (Group A, n = 79), adolescents (Group B, n = 19), primary school children (Group C, n = 32) and third trimester pregnant women (Group D, n = 60) were all unimodal, normal and not different from each other (A = 0.57+/-0.64%, B = 0.87+/-0.45%, C = 0.81+/-0.87% and D = 0.35+/-0.48%). The distribution of insulin binding in the cord sera of consecutive newborns (n = 428) born between October and the following May, however, was bimodal. The first distribution, included 400 sera, was symmetrical and not different (0.79+/-0.45%) from groups A, B, C and D. The second distribution comprised the remaining 28 sera (7% of the total sample) with insulin-displaceable binding values in an IDW-validated radio assay ranging from 2.2% to 31.1%. The appearance of IAA was not HLA-restricted, but the frequency of IAA+ samples was seen to vary over five consecutive months. The timing is consistent with acute viral infection, but the implications for future insulin dependent diabetes will await long-term follow-up of the children and mothers involved.

Adolescent↗
PubMed2000

Growth behaviour and indole acetic acid (IAA) production by a Rhizobium isolated from root nodules of Alysicarpus vaginalis DC.

From the root nodules of Alysicarpus vaginalis DC, the symbiont was isolated and identified as a Rhizobium sp. The bacteria produced a high amount (107 microg/ml) of indole acetic acid (IAA) in culture from tryptophan supplemented yeast extract mannitol medium. The isolate preferred L-isomer of tryptophan for maximum IAA production. The production was maximum when the bacteria reached its stationary phase of growth. The production of IAA could be increased up to 70% over yeast extract glucose medium by supplementing ZnSO4, 7H2O (0.5 microg/ml). L-asparagine (0.2%) and sodium dodecyl sulfate (1.0 microg/ml). The possible relationship between the rhizobial IAA production and legume-rhizobia symbiosis is discussed.

Carbon↗
PubMedDate not supplied

[Inhibition of IAA-induced growth of wheat coleoptile fragments by chitin-chitosan oligomers].

We studied the comparative effects of the phytohormone indolylacetic acid (IAA) and chitooligosaccharides (5-10 kDa, degree of deacetylation 35%) on the growth of coleoptile fragments of 3-day wheat germlings. IAA (10 mg/l) stimulated elongation of coleoptile fragments by 80%, as compared to the control (water). Chitooligosaccharides at 0.01-1500 mg/l or higher did not exert auxin-like effects, but at 100 mg/l or higher, suppressed elongation of the coleoptile fragments, as compared to the control (water). Incubation of coleoptile fragments in solutions containing both IAA and chitooligosaccharides (100 mg/l or higher) suppressed their IAA-induced elongation, which correlated with the inhibition of growth of 3-day wheat germlings after wetting seeds in solutions of chitooligosaccharides. It has been proposed that the phytohormone-like properties of chitooligosaccharides can be related to changes in the endogenous balance of phytohormones in plants.

Chitin↗
PubMedDate not supplied

[Effect of IAA on the content of RNA in the cells and isolated nuclei of Aspergillus oryzae].

The content of RNA in mycelium and isolated nuclei of Aspergillus oryzae 3-9-15 was studied after its growth during two days on the modified Capek medium containing 0.01 and 10 mg% of IAA. A direct correlation has been established between the extracellular concentration of IAA and its content in the mycelium and isolated nuclei of the fungus. The stimulating effect of the extracellular IAA on the content of RNA in the isolated nuclei was optimal after one hour of incubation in the Capek medium containing 0.01 or 10 mg% of IAA.

Aspergillus↗
PubMed2002

[Effects of NaCl stress on seedling growth and IAA metabolism of sweet potato and its relation to salt-tolerance].

Seedlings of three sweet-potato (Ipomoea batatas) cultivars with different salt-tolerance were stressed with different concentrations of NaCl during the seedling stage. Plant growth, leaf area growth, and IAA content decreased with increasing NaCl concentration, while the activities of POD and IAA oxidase increased. The extent of plant growth, leaf area growth and IAA content decrease and the extent of POD and IAA oxidase activity increase were larger in sensitive cultivar than those in moderately tolerant and tolerant cultivars. In addition, the content of chlorogenic acid increased under NaCl stress. Chlorogenic acid content reached its peak value at 170 mmol.L-1 of NaCl in sensitive and moderately tolerant cultivars and 225 mmol.L-1 of NaCl in tolerant cultivar. Chlorogenic acid content decreased with increasing NaCl concentration, but it was higher than that of the control.

Chlorogenic Acid↗
PubMed2004

Induced resistance in tomato plants by IAA against Fusarium oxysporum lycopersici.

The phytohormone IAA (indol-3-acetic acid) was tested in vitro on growth of tomato wilt pathogen Fusarium oxysporum lycopersici. The hormone reduced spore germination, mycelial dry weight and protein content. Such reduction was matched with the elevation in the hormone concentration. The in vivo application of IAA to soil of the uninoculated plants (controls) improved growth and yielded longer shoot and root, particularly at low concentrations. Moreover, the hormone could prevent completely any chance for disease incidence by soil pathogens. Presence of IAA in soil of inoculated plants not only reduced the infection rate but also increased plant growth, causing that they appeared healthy and normal. Disease suppression in tomato plants, exerted by application of IAA, was achieved through either increasing plant growth, exerting a direct harmful effect on the target pathogen and/or inducing resistance in host tissue. The induced resistance was correlated with induction of certain secondary metabolites which may have a role in increasing tolerance in tomato plants to the pathogen.

Antifungal Agents↗
PubMed1977

A scanning electron microscopic study of IAA-induced tumors in bean (Phaseolus vulgaris L.) embryos.

A scanning electron microscopic study of indole-3-acetic acid (IAA) induced tumour in the hypocotyl region of bean embryos shows a distinct morphological, structural and topographical change from the non-treated bean embryos. The IAA-induced tumour surface, in the hypocotyl region, shows distinct cell enlargement, some cellular proliferation in the parenchymatous tissue, total destruction of the epidermis and stomata and some variation in trichome structures. In dole-3-acetic acid inhibits the normal growth of the epicotyl, and, as age progresses, adventitious roots appear all over the surface. When IAA-depletion occurs, epicotyl growth resumes, which indicates that this tumour formation in bean embryos is an IAA-dependent tumour.

Indoleacetic Acids↗
PubMed1978

Cytological study of inhibitory effects of IAA on the root growth in the Pinus silvestris.

It has been found that IAA at the concentrations 0.1--10.0 ppm retards the pine root growth and decreases mitotic activity. All the applied concentrations of this hormone cause a decrease of the 3H-thymidine incorporation index and inhibit endomitotic polyploidization in suprameristematic segments. The mean time of the cell cycle prolongs and the heterogeneity of cellular populations increases in parallel with the increase of IAA concentration. The template activity of DNA decreases under the influence of the applied concentrations of IAA; this effect is being particularly strong in the meristematic root segment. IAA exerts also an inhibitory influence on protein synthesis, especially reducing the synthesis of histones.

DNA↗
PubMed2005

Role of a Ca2+-ATPase induced by ABA and IAA in the generation of specific Ca2+ signals.

The control of the Ca(2+)-ATPase gene (LCA1) that encodes two different membrane-located isoforms by two antagonic phytohormones, ABA and IAA, has been investigated. Strikingly both the growth regulators induce the LCA1 expression. By using a protoplast transient system, the cis-acting DNA elements responding to both, abiotic stress (ABA) and normal development (IAA), are dissected. ABA triggered a 4-fold increase in the GUS-activity. A single ACGT motif responsible for most of the LCA1 mRNA induction was localized at an unexpectedly large distance (1577 bp) upstream of the translational start. In the case of IAA, although there is a TGTCTC sequence that is known to be an important cis-acting element, two TGA motifs play a more critical role. It is proposed that the Ca(2+)-ATPase isoforms might intervene in the generation of specific Ca(2+) signals by restoring steady-state Ca(2+) levels, modulating both frequency and amplitude of Ca(2+) waves via wave interference.

Abscisic Acid↗
PubMed2004

Effects of cadmium and copper on peroxidase, NADH oxidase and IAA oxidase activities in cell wall, soluble and microsomal membrane fractions of pea roots.

Twelve-day-old seedlings of pea (Pisum sativum L.) that were treated for 4 days by 20 and 100 micromol/l Cd(NO3)2 or CuSO4 showed a growth reduction in all organs. From root protein extracts, the activities of guaiacol peroxidase (GPX; EC 1.11.1.7), ascorbate peroxidase (APX; EC 1.11.1.11), coniferyl alcohol peroxidase (CAPX), NADH oxidase, and indole-3-acetic acid (IAA) oxidase were measured in covalently--and ionically--[symbol: see text] bound cell wall, soluble, and microsomal membrane fractions. With the exception of 20 micromol/l Cu, metal treatments enhanced GPX activity in all fractions. Only IAA oxidase activity was metal-elevated in the covalently bound cell wall fraction, while the ionic one showed Cd stimulation for all assayed enzymic activities. These effects were not entirely observed in Cu-treated plants, since APX and IAA oxidase activities were only enhanced in this fraction. However, soluble extract showed stimulation of APX activity, while in the microsomal fraction metal exposure also increased the activities of CAPX and NADH oxidase. Differential responses of root cell fractions to the presence of cadmium and copper ions are discussed in regard to the contribution of their enzymic capacities in antioxidant, lignification, and auxin degradation pathways. Comparisons between metals and dose effects are also underlined.

Cadmium Compounds↗
PubMed2005

Thidiazuron influences the endogenous levels of cytokinins and IAA during the flowering of isolated shoots of Dendrobium.

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. The results revealed that the presence of 1.8microM TDZ had a profound effect on the endogenous cytokinins (CKs) and IAA levels of the explants, when compared to those grown on a TDZ-free medium. A significant increase in CKs (especially [9R]iP and [9R]Z) and IAA in the first samples (taken at day 5) grown on TDZ-enriched medium was associated with flower induction, while a second increase in the level of these hormones after 25d of culture was related to flower development. The histological changes detected in the shoot apical meristem of explants grown in the presence of 1.8microM TDZ during 30d of culture are also described. Based on these findings, it is suggested that both auxin and CKs seem to be involved with the floral transition of Dendrobium Second Love in vitro. However, a possible direct effect of TDZ on flower formation is not discarded.

Adenosine↗
PubMed2004

Brassinolides and IAA induce the transcription of four alpha-expansin genes related to development in Cicer arietinum.

Four different cDNAs encoding alpha-expansins have been identified in Cicer arietinum (Ca-EXPA1, Ca-EXPA2, Ca-EXPA3 and Ca-EXPA4). The shared amino acid sequence similarity among the four alpha-expansin proteins ranged from 67 to 89%. All of them display common characteristics such as molecular mass (around 24 kDa), amino acid numbers, and also the presence of a signal peptide. The transcription pattern of chickpea alpha-expansin genes in seedlings and plants suggests a specific role for each of the four alpha-expansins in different phases of development or in different plant organs. High levels of Ca-EXPA2 transcripts coincide with maximum epicotyl and stem growth, indicating an important involvement of this particular alpha-expansin in elongating tissues. Ca-EXPA3 would be related to radicle development, while Ca-EXPA4 seems to be involved in pod development. A considerable increase in the level of all Ca-EXPA transcripts accompanied the indole acetic acid (IAA) plus brassinolide (BR)-induced elongation of excised epicotyl segments. This IAA + BR induction was seen even for the chickpea expansin genes whose transcription was not affected by IAA or BR alone.

Amino Acid Sequence↗
PubMed2000

Cytoskeletal inhibitors suppress the stomatal opening of Vicia faba L. induced by fusicoccin and IAA.

Stomatal movement is governed by osmotic potential, in which K(+) concentration plays the dominant role. Our previous work has shown that both microtubules and microfilaments are involved in regulating stomatal movement. In the present investigation the relationships between cytoskeletal components and K(+) fluxes in stomatal opening were addressed by using fusicoccin (FC), indoleacetic acid (IAA), and cytoskeletal inhibitors to treat both epidermal strips and protoplasts of guard cells. The results revealed that FC and IAA induced stomatal opening with or without KCl in the dark. Also FC or IAA induced guard cell protoplast swelling in the dark even without added KCl. However, the induction was partially suppressed when strips and protoplasts were pretreated with cytochalasin B (CB), an inhibitor of F-actin polymerization, or oryzalin, an inhibitor of plant microtubule polymerization. Thus our preliminary results indicate for the first time that microtubules and microfilaments can affect stomatal opening independently of K(+) fluxes.

Journal Article↗