Comparative indole-3-acetic Acid levels in the slender pea and other pea phenotypes

Free indole-3-acetic acid levels were measured by gas chromatography-mass spectrometry in three ultra-tall `slender' Pisum sativum L. lines differing in gibberellin content. Measurements were made for apices and stem elongation zones of light-grown plants and values were compared with wild-type, dwarf, and nana phenotypes in which internode length is genetically regulated, purportedly via the gibberellin level. Indole-3-acetic acid levels of growing stems paralleled growth rates in all lines, and were high in all three slender genotypes. Growth was inhibited by p-chlorophenoxyisobutyric acid, demonstrating the requirement of auxin activity for stem elongation, and also by the ethylene precursor 1-aminocyclopropane-1-carboxylic acid. It is concluded that the slender phenotype may arise from constant activation of a gibberellin receptor or transduction chain event leading directly or indirectly to elevated levels of indole-3-acetic acid, and that increased indole-3-acetic acid levels are a significant factor in the promotion of stem elongation.     

Gibberellin-enhanced indole-3-acetic acid biosynthesis: D-Tryptophan as the precursor of indole-3-acetic acid

Stem segments excised from light-grown Pisum sativum L. (cv. Little Marvel) plants elongated in the presence of indole-3-acetic acid and its precursors, except for L-tryptophan, which required the addition of gibberellin A, for induction of growth. Segment elongation was promoted by D-tryptophan without a requirement for gibberellin, and growth in the presence of both D-tryptophan and L-tryptophan with gibberellin A3, was inhibited by the D-aminotransferase inhibitor D-cycloserine. Tryp-tophan racemase activity was detected in apices and promoted conversion of L-tryptophan to the D isomer; this activity was enhanced by gibberellin A3. When applied to apices of intact untreated plants, radiolabeled D-tryptophan was converted to indole-3-acetic acid and indoleacetylaspartic acid much more readily than L-tryptophan. Treatment of plants with gibberellin A3, 3 days prior to application of labeled tryptophan increased conversion of L-tryptophan to the free auxin and its conjugate by more than 3-fold, and led to labeling of N-malonyl-D-tryptophan. It is proposed that gibberellin increases the biosynthesis of indole-3-acetic acid by regulating the conversion of L-tryptophan to D-tryptophan, which is then converted to the auxin.     

Synergism between Gibberellin and Auxin in the Growth of Intact Tomato

Gibberellin A_4&7 was more effective than gibberellic acid in increasing shoot elongation when applied to the apex of intact Lycopersicum esculentum seedlings of Tiny Tim, a dwarf cultivar, and Winsall, a tall cultivar. After 14 days, gibberellic acid and gibberellin A_4&7 stimulated growth of the dwarf more than the tall tomato. In tall tomato the application of indole-3-acetic acid alone (6.1 μg/plant) showed an inhibitory growth effect, but when applied with 17.5 μg per plant of gibberellic acid, it had a synergistic effect at 7 days but not at 14 days. When the auxin concentration was reduced to 0.61 μg per plant a synergistic effect was observed on tall plants at 7 and 14 days between indole-3-acetic acid and gibberellic acid. Application of gibberellin A_4&7 with auxin did not give a synergistic response in tall or dwarf tomato.     

Gibberellin-auxin interaction in pea stem elongation

Joint application of gibberellic acid and indole-3-acetic acid to excised stem sections, terminal cuttings, and decapitated plants of a green dwarf pea results in a markedly synergistic growth response to these hormones. Synergism in green tall pea stem sections is comparatively small, although growth is kinetically indistinguishable from similarly treated dwarf sections.

Gibberellin-induced growth does not appear to be mediated through its effect on auxin synthesis, since gibberellin pretreatment of dwarf cuttings fails to elicit an enhanced tryptophan-induced growth response of sections, whereas auxin-induced growth is strongly enhanced. Also, tryptophan-gibberellin synergism is not significant in sections and cuttings of green dwarf peas, while auxin-gibberellin synergism is.

Administration of gibberellic acid prior to indole-3-acetic acid results in greatly increased growth. In reversed order, the application fails to produce any synergistic interaction. This indicates that gibberellin action must precede auxin action in growth regulation.

     

Increased endogenous gibberellin level inhibits root growth of Pinus massoniana Lamb. plantlets during long-term subculture

In Vitro Cellular & Developmental Biology - Plant - In this study, we investigated the roles of the plant hormones indole-3-acetic acid (IAA) and gibberellin (GA) in regulating Pinus massoniana...     

Determination of phytohormones in phloem exudate from tree species by radioimmunoassay

A sensitive and specific radioimmunoassay was used to determine quantitatively four of the most important phytohormones in the phloem exudate from 14 different tree species of 8 genera. For cytokinins and indole-3-acetic acid (IAA) we found higher concentrations than those reported previously for other species. The gibberellin values were of the same order of magnitude as in earlier analyses (with different methods) of tree phloem exudates, but lower than the ones reported for Ricinus. Free abscisic acid (ABA) was found in tree phloem exudates in similar concentrations as before in Yucca or palm phloem exudate, but at considerably lower ones than reported for Ricinus and in Lupinus phloem exudate.Abbreviations IAA indole-3-acetic acid - ABA abscisic acid - GA gibberellic acid     

Tryptophol Formation by Zygosaccharomyces priorianus

Zygosaccharomyces priorianus converted L-tryptophan to tryptophol and to small quantities of indole-3-acetic acid. Neither tryptophol nor indole-3-acetic acid was metabolized when added separately to growing cultures. The possible intermediacy of indole-3-pyruvic acid, indole-3-acetaldehyde, and tryptamine in the degradation of L-tryptophan was tested by feeding these compounds to Z. priorianus and Saccharomyces cerevisiae. Indole-3-pyruvic acid and indole-3-acetaldehyde were converted to tryptophol and indole-3-acetic acid, with the latter accumulating only in small amounts. Tryptamine was converted to its N-acetyl derivative by these organisms. A qualitative study was made on the metabolism of L-phenylalanine, L-tyrosine, and L-5-hydroxytryptophan by these organisms. Like L-tryptophan, these amino acids were metabolized to their respective alcohol and acid derivatives. Of a large number of organisms tested, the yeasts possessed the highest capacity for degrading L-tryptophan to tryptophol.     

Auxin, Gibberellin, Cytokinin and Abscisic Acid Production in Some Bacteria

Summary In this study, auxin (indole-3-acetic acid), gibberellin, cytokinin (zeatin) and abscisic acid production were investigated in the culture medium of the bacteria Proteus mirabilis, P. vulgaris, Klebsiella pneumoniae, Bacillus megaterium, B. cereus, Escherichia coli. To determine the levels of these plant growth regulators, high performance liquid chromatography (HPLC) technique was used. Our findings show that the bacteria used in this study synthesized the plant growth regulators, auxin, gibberellin, cytokinin and abscisic acid.     

Changes in Gibberellin-Like Substances and Indole-3-Acetic Acid in Picea abies during the Period of Shoot Elongation

Grafted clones of Picea abies (L.) Karst. were used for the study. A very rapid and conspicuous rise in the content of gibberellin-like substances chromatographically similar to gibberellin A₁, and of indole-3-acetic acid, occurred during the brief period of most rapid shoot elongation. A few days later, when the shoot growth had terminated, very small amounts of both compounds could be detected. The changes in the qualitative pattern of gibberellin-like substances were consistent with a suggested interconversion pathway leading from non-polar to increasingly polar compounds     

Role of Ascorbic Acid in Bud Development

Ascorbic acid was found to increase bud development in Pisum sativum L. The interactions of ascorbic acid with indole-3-acetic acid, kinetin and gibberellic acid were studied. It was found that ascorbic acid promoted bud growth and overcame the inhibitory effect of auxin. When applied with gibberellin, bud growth was greatly enhanced. Ascorbic acid promoted bud development in red light only; it did not in far-red or dark.     

Biosynthesis of auxin by the gram-positive phytopathogen Rhodococcus fascians is controlled by compounds specific to infected plant tissues

The role and metabolism of indole-3-acetic acid in gram-negative bacteria is well documented, but little is known about indole-3-acetic acid biosynthesis and regulation in gram-positive bacteria. The phytopathogen Rhodococcus fascians, a gram-positive organism, incites diverse developmental alterations, such as leafy galls, on a wide range of plants. Phenotypic analysis of a leafy gall suggests that auxin may play an important role in the development of the symptoms. We show here for the first time that R. fascians produces and secretes the auxin indole-3-acetic acid. Interestingly, whereas noninfected-tobacco extracts have no effect, indole-3-acetic acid synthesis is highly induced in the presence of infected-tobacco extracts when tryptophan is not limiting. Indole-3-acetic acid production by a plasmid-free strain shows that the biosynthetic genes are located on the bacterial chromosome, although plasmid-encoded genes contribute to the kinetics and regulation of indole-3-acetic acid biosynthesis. The indole-3-acetic acid intermediates present in bacterial cells and secreted into the growth media show that the main biosynthetic route used by R. fascians is the indole-3-pyruvic acid pathway with a possible rate-limiting role for indole-3-ethanol. The relationship between indole-3-acetic acid production and the symptoms induced by R. fascians is discussed.     

Proposed Model for the Peroxidase-Catalyzed Oxidation of Indole-3-acetic Acid in the Presence of the Inhibitor Ferulic Acid

Linear increments in ferulic acid concentration produce logarithmic increases in the ferulic acid-induced lag periods prior to the peroxidase-catalyzed oxidation of indole-3-acetic acid in a system containing 2,4-dichlorophenol and MnCl₂ in acetate buffer at pH 5.6. Maintaining the ratio of indole-3-acetic acid to ferulic acid constant at 100 while linearly raising the ferulic acid concentration results in linear increases in the lag period. Both indole-3-acetic acid and ferulic acid are substrates of horseradish peroxidase in the presence of H₂O₂, and indole-3-acetic acid competitively inhibits the oxidation of ferulic acid. A model for the enzymatic oxidation of indole-3-acetic acid catalyzed by peroxidase is proposed.     

Promotion of peroxidase activity in the cell wall of Nicotiana

Peroxidase catalyzes the oxidation of indole-3-acetic acid. The primary products of this reaction stimulate growth in plants. Therefore, our concept is that an increase in peroxidase activity will increase the effect of indole-3-acetic acid as a growth hormone. Our objective was to study the effect of 2,3,5-triiodobenzoic acid, a growth regulator, on isoperoxidases in the cell wall and cytoplasm of Nicotiana. Isoperoxidases from the cell wall and cytoplasmic fractions were separated by acrylamide gel electrophoresis. We found that 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase peroxidase activity in the cell wall. Since both 2,3,5-triiodobenzoic acid and indole-3-acetic acid increase the activity of the same isoperoxidase, we conclude that 2,3,5-triiodobenzoic acid synergizes rather than antagonizes auxin action, and we suggest that this increase in indole-3-acetic acid oxidase activity sensitizes plant tissues to auxin.     

解淀粉芽胞杆菌HZ-12中ysnE参与吲哚-3-乙酸合成的代谢途径研究

【目的】吲哚-3-乙酸是调控植物生长发育和生理活动的重要激素,吲哚-3-乙酸N-乙酰转移酶YsnE在吲哚-3-乙酸合成中发挥重要作用,本研究拟解析解淀粉芽胞杆菌中YsnE参与吲哚-3-乙酸合成的代谢途径。【方法】通过基因ysnE缺失和强化表达,分析ysnE对吲哚-3-乙酸合成影响,结合吲哚-3-乙酸合成中间物(吲哚丙酮酸、吲哚乙酰胺、色胺和吲哚乙腈)添加和体外酶转化实验,解析ysnE参与吲哚-3-乙酸合成的代谢途径。【结果】明确了YsnE在解淀粉芽胞杆菌HZ-12吲哚-3-乙酸合成中发挥重要作用。发现ysnE缺失菌株中的吲哚丙酮酸、吲哚乙酰胺和吲哚乙腈利用显著降低,揭示了YsnE主要发挥吲哚丙酮酸脱羧酶YclB和吲哚乙酰胺水解酶/腈水解酶/腈水合酶YhcX的功能,并通过参与吲哚丙酮酸、吲哚乙酰胺和吲哚乙腈途径来影响吲哚-3-乙酸合成。【结论】初步揭示了YsnE通过影响吲哚丙酮酸、吲哚乙酰胺和吲哚乙腈途径参与吲哚-3-乙酸合成的代谢机理,为吲哚-3-乙酸合成途径解析和代谢工程育种构建吲哚-3-乙酸高产菌株奠定了基础。     

Auxin activity of 3-methyleneoxindole in wheat

A product of the enzymatic oxidation of indole-3-acetic acid, 3-methyleneoxindole, is at least 50-fold more effective than indole-3-acetic acid in stimulating the growth of wheat (Triticum vulgare, red variety) coleoptiles. Ethylenediaminetetra-acetic acid can antagonize the growth-stimulating properties of the parent compound, indole-3-acetic acid, presumably by chelating Mn²⁺, which is required for the enzymatic oxidation of indole-3-acetic acid. The growth stimulating effect of 3-methyleneoxindole, a product of the blocked reaction, on the other hand, is still evident in the presence of ethylenedia-minetetraacetic acid. In the presence of 2-mercaptoethanol, indole-3-acetic acid fails to stimulate the elongation of wheat coleoptiles. The property of binding to sulfhydryl compounds including 2-mercaptoethanol is unique to 3-methyleneoxindole among indole-3-acetic acid and its oxidation products. These findings suggest that 3-methyleneoxindole is an obligatory intermediate in indole-3-acetic acid induced elongation of wheat coleoptiles.     

Fluctuation in levels of endogenous plant hormones in ovules of normal and mutant cotton during flowering and their relation to fiber development

The contents of indole-3-acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA), and cytokinins were determined in ovules of normal cotton (Tm-1) and a kind of fiber differentiation mutant (Xin) before and after flowering by enzyme-linked immunosorbent assays. It was found that 24 h before flowering, a peak of IAA content was observed in ovules of Tm-1, whereas in ovules of Xin, a low level of IAA was determined. From –1 day (1 day before flowering) to +3 days (3 days after flowering), GA₁₊₃ levels in ovules of Xin were 40–70% lower than those of Tm-1; GA₄₊₇ levels were very low, and there was no visible difference in GA₄₊₇ content between normal and mutant cotton. The ABA content in ovule of Tm-1 decreased by 70% 3 days after flowering, whereas that of Xin only decreased by 20%. The levels of cytokinins in ovules of Tm-1 decreased after flowering, and those of Xin kept up a steady increase.Abbreviations IAA indole-3-acetic acid - GA gibberellin - ABA abscisic acid - ELISA enzyme-linked immunosorbent assay - FW fresh weight - PBS phosphate-buffered saline - iPA isopentenyladenosine - ZR zeatin riboside - DHZR dihydrozeatin riboside - CTK cytokinin     

Role of Auxin in Induction of Polarity in Fucus vesiculosus Zygotes

We studied the effects of auxin (indole-3-acetic acid) on formation of the primary polarity axis in zygotes of the brown algae Fucus vesiculosusL. Within the first 2.5 h after fertilization, the zygotes release this phytohormone in the ambient medium. The treatment of developing zygotes with the inhibitor of indole-3-acetic acid transport from the cell 2,3,5-triiodobenzoic acid at 5 mg/l arrests the auxin secretion and leads to its accumulation in the cells. This causes a significant delay in zygote polarization. The treatment of zygotes with the exogenous indole-3-acetic acid at 1 mg/l stimulates cell polarization and formation of a rhizoid protuberance. When auxin was added to the medium with triiodobenzoic acid, the inhibitory effect of the latter was eliminated. It has been proposed that the content of indole-3-acetic acid in the ambient medium is a key factor in the induction of polarity of the F. vesiculosus zygotes.     

Biosynthesis of Auxin by the Gram-Positive Phytopathogen Rhodococcus fascians Is Controlled by Compounds Specific to Infected Plant Tissues

The role and metabolism of indole-3-acetic acid in gram-negative bacteria is well documented, but little is known about indole-3-acetic acid biosynthesis and regulation in gram-positive bacteria. The phytopathogen Rhodococcus fascians, a gram-positive organism, incites diverse developmental alterations, such as leafy galls, on a wide range of plants. Phenotypic analysis of a leafy gall suggests that auxin may play an important role in the development of the symptoms. We show here for the first time that R. fascians produces and secretes the auxin indole-3-acetic acid. Interestingly, whereas noninfected-tobacco extracts have no effect, indole-3-acetic acid synthesis is highly induced in the presence of infected-tobacco extracts when tryptophan is not limiting. Indole-3-acetic acid production by a plasmid-free strain shows that the biosynthetic genes are located on the bacterial chromosome, although plasmid-encoded genes contribute to the kinetics and regulation of indole-3-acetic acid biosynthesis. The indole-3-acetic acid intermediates present in bacterial cells and secreted into the growth media show that the main biosynthetic route used by R. fascians is the indole-3-pyruvic acid pathway with a possible rate-limiting role for indole-3-ethanol. The relationship between indole-3-acetic acid production and the symptoms induced by R. fascians is discussed.     

Translocation of Radiolabeled Indole-3-Acetic Acid and Indole-3-Acetyl-myo-Inositol from Kernel to Shoot of Zea mays L.

Either 5-[³H]indole-3-acetic acid (IAA) or 5-[³H]indole-3-acetyl-myo-inositol was applied to the endosperm of kernels of dark-grown Zea mays seedlings. The distribution of total radioactivity, radiolabeled indole-3-acetic acid, and radiolabeled ester conjugated indole-3-acetic acid, in the shoots was then determined. Differences were found in the distribution and chemical form of the radiolabeled indole-3-acetic acid in the shoot depending upon whether 5-[³H]indole-3-acetic acid or 5-[³H]indole-3-acetyl-myo-inositol was applied to the endosperm. We demonstrated that indole-3-acetyl-myo-inositol applied to the endosperm provides both free and ester conjugated indole-3-acetic acid to the mesocotyl and coleoptile. Free indole-3-acetic acid applied to the endosperm supplies some of the indole-3-acetic acid in the mesocotyl but essentially no indole-3-acetic acid to the coleoptile or primary leaves. It is concluded that free IAA from the endosperm is not a source of IAA for the coleoptile. Neither radioactive indole-3-acetyl-myo-inositol nor IAA accumulates in the tip of the coleoptile or the mesocotyl node and thus these studies do not explain how the coleoptile tip controls the amount of IAA in the shoot.     

Concentrations of Indole-3-acetic Acid and Its Esters in Avena and Zea

An isotope-dilution method has been developed for the assay of free indole-3-acetic acid and ester indole-3-acetic acid as measured by indole-3-acetic acid liberated by mild alkaline hydrolysis. Application of this method to seedlings of Avena sativa and Zea mays indicates the upper limit of free indole-3-acetic acid in Avena to be about 16 μg per kg and in Zea, about 24 μg. The amount of 1 n alkali-labile indole-3-acetic acid in Zea is about 330 μg per kg and there is very little 1 n alkali-labile IAA in Avena. A chemical characterization of the indole-3-acetic acid of Avena and a confirmation of the chemical characterization of the indole-3-acetic acid of Zea is presented.