Different Behaviour of Indole-3-Acetic Acid and Indole-3-Butyric Acid in Stimulating Lateral Root Development in Rice (Oryza sativa L.)

The plant hormone auxin has been shown to be involved in lateral root development and application of auxins, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA), increases the number of lateral roots in several plants. We found that the effects of two auxins on lateral root development in the indica rice (Oryza sativa L. cv. IR8) were totally different from each other depending on the application method. When the roots were incubated with an auxin solution, IAA inhibited lateral root development, while IBA was stimulatory. In contrast, when auxin was applied to the shoot, IAA promoted lateral root formation, while IBA did not. The transport of [³H]IAA from shoot to root occurred efficiently (% transported compared to supplied) but that of [³H]IBA did not, which is consistent with the stimulatory effect of IAA on lateral root production when applied to the shoot. The auxin action of IBA has been suggested to be due to its conversion to IAA. However, in rice IAA competitively inhibited the stimulatory effect of IBA on lateral root formation when they were applied to the incubation solution, suggesting that the stimulatory effect of IBA on lateral root development is not through its conversion to IAA.     

Involvement of Abscisic Acid and Indole-3-acetic Acid in the Flowering of Pharbitis nil

The involvement of abscisic acid (ABA) and indole-3-acetic acid (IAA) in the regulation of flowering of Pharbitis nil was investigated through exogenous applications and analyses of endogenous levels. Both hormones inhibited the flowering of P. nil when they were applied before or after a single 15-h dark treatment. The inhibitory effect of ABA and IAA was significant when they were applied before the dark treatment, and the application to plumules was more effective than that to cotyledons. In all applications, the inhibitory effect of IAA was stronger than that of ABA. Endogenous levels of ABA and IAA in the plumules were compared between flower-inductive (15-h dark treatment) and noninductive (continuous light) light conditions. There was no significant difference in the ABA level between light and dark conditions, whereas the level of IAA was decreased by the dark treatment. These results suggest that biosynthesis and/or catabolism of IAA is affected by the light treatment and therefore may be involved in the regulation of early flowering processes in the apex. The inhibitory effects of ABA and IAA were reversed by an application of gibberellin A₃, indicating that gibberellin A₃ counteracts the flowering processes affected by ABA and IAA. Application of aminoethoxyvinylglycine restored the flowering response inhibited by IAA, which suggests the possibility that the inhibitory effect of IAA is the result of enhanced ethylene biosynthesis. Received November 22, 1996; accepted February 17, 1997     

Enhancement of Lipid Peroxidation by Indole-3-Acetic Acid and Derivatives: Substituent Effects

The peroxidation of liposomes by a haem peroxidase and hydrogen peroxide in the presence of indole-3-acetic acid and derivatives was investigated. It was found that these compounds can accelerate the lipid peroxidation up to 65 fold and this is attributed to the formation of peroxyl radicals that may react with the lipids, possibly by hydrogen abstraction. The peroxyl radicals are formed by peroxidase-catalyzed oxidation of the enhancers to radical cations which undergo cleavage of the carbon-carbon bond on the side-chain to yield CO2 and carbon-centred radicals that rapidly add oxygen. In competition with decarboxylation, the radical cations deprotonate reversibly from the Nl position. Rates of decarboxylation,pK_a values and rate of reaction with the peroxidase compound I indicate consistent substituent effects which, however, can not be quantitatively related to the usual Hammett or Brown parameters. Assuming that the rate of decarboxylation of the radical cations taken is a measure of the electron density of the molecule (or radical), it is found that the efficiency of these compounds as enhancers of lipid peroxidation increases with increasing electron density, suggesting that, at least in the model system, the oxidation of the substrates is the limiting step in causing lipid peroxidation.     

Enhancement of Lipid Peroxidation by Indole-3-Acetic Acid and Derivatives: Substituent Effects

The peroxidation of liposomes by a haem peroxidase and hydrogen peroxide in the presence of indole-3-acetic acid and derivatives was investigated. It was found that these compounds can accelerate the lipid peroxidation up to 65 fold and this is attributed to the formation of peroxyl radicals that may react with the lipids, possibly by hydrogen abstraction. The peroxyl radicals are formed by peroxidase-catalyzed oxidation of the enhancers to radical cations which undergo cleavage of the carbon-carbon bond on the side-chain to yield CO2 and carbon-centred radicals that rapidly add oxygen. In competition with decarboxylation, the radical cations deprotonate reversibly from the Nl position. Rates of decarboxylation,pK_a values and rate of reaction with the peroxidase compound I indicate consistent substituent effects which, however, can not be quantitatively related to the usual Hammett or Brown parameters. Assuming that the rate of decarboxylation of the radical cations taken is a measure of the electron density of the molecule (or radical), it is found that the efficiency of these compounds as enhancers of lipid peroxidation increases with increasing electron density, suggesting that, at least in the model system, the oxidation of the substrates is the limiting step in causing lipid peroxidation.     

Enhancing of Phytoremediation Efficiency Using Indole-3-Acetic Acid (IAA)

In this study, a pot experiment using Solanum nigrum L. grown in cadmium-contaminated soil was conducted in a greenhouse. Indole-3-acetic acid (IAA) was applied at three different concentrations (1 mg L^?1, 10 mg L^?1, and 100 mg L^?1) to examine the effects on phytoremediation efficiency. According to the experimental results, IAA increased the shoot biomass of S. nigrum significantly, by 124% at the highest concentration used, and increased the Cd concentration in the shoot of S. nigrum by 16%. The Cd extraction amount from a single plant was increased by up to 158%, demonstrating potential practical application for remediation practice.     

利用大肠杆菌细胞工厂生产吲哚-3-乙酸的研究

目的:利用重组大肠杆菌全细胞转化色氨酸生产IAA.方法:在大肠杆菌胞内构建两条全新的IAA合成途径,即吲哚-3-乙酰胺(indole-3-acetamide,IAM)途径和色胺(tryptamine,TRP)途径.结果:IAM途径涉及两个酶,分别是色氨酸-2-单加氧酶(IAAM)和酰胺酶(AMI1),构建好的重组大肠杆...     

热胁迫对不同发育阶段大豆生长素和脱落酸含量的影响(英文)

大豆等植物体内细胞受热或受其它理化因素（如：重金属离子、乙醇、氨基酸类似物）、以及缺氧、DNA损伤、病毒感染等病理因素刺激后,促发应激反应,启动某些基因表达,能产生各种生理活性物质以及各种酶类,共同调控代谢过程和某些激素的活动,如：吲哚乙酸（IAA）、脱落酸（ABA）等。这些内源IAA和ABA共同作用,调节着大豆的抗逆性,从而影响着大豆的农艺性状。本试验对华北生态型的六个大豆栽培种,进行热激处理;取其第三片展开叶,测其内源IAA和ABA含量。这些品种分别是：早熟17,诱处4号,诱变31,耐阴黑豆、科丰6号和科丰34（Tan．1）。初花期,第一天热激（43～45℃,4h）后,它们的IAA和ABA水平均显著高于对照（30～33℃）（Fig．1）。然而,在连续一天热激后（43～45℃,4h／d）,大多数品种的IAA和ABA比第一天减少（Fig．2）。盛花期连续热激处理二天（43～45℃,4h／d）,IAA水平一般低于对照（3～33℃）,半数品种ABA水平也低于对照（Fig．3）。结荚期连续两天热激后（45℃,4h／d）,IAA和ABA含量均显著高于对照（30～33℃）（Fig．4）。     

在吲哚乙酸不同位点偶联载体蛋白对其抗体特异性的影响

分别选择吲哚乙醇分子上的Ｃ１位羧基和吲哚环上的Ｎ位作为偶联载体蛋白的位点,用混合酸酐法和甲醛搭桥法分别合成了两种免疫原ＩＡＡ—ＣＯ—ＮＨ一ＨＳＡ和ＩＡＡ－Ｎ－ＢＳＡ,并进而制得了对吲哚乙酸侧链识别能力不同的两种多克隆抗体,分别可特异识别甲酯化ＩＡＡ和游离态ＩＡＡ;用碳化二亚胺法和甲醛搭桥法分别合成ＩＡＡ—ＣＯ—ＮＨ－ＢＳＡｂＩＡＡ—Ｎ—ＯＶＡ两种复合物,以之为包被物,建立了两种ＩＡＡＥＬＩＳＡ。其灵敏度分别为０．３５ｐｍｏｌ和１．８０ｐｐｍｏｌ;检测范围分别为０．７８～８００ｐｍｏｌ和１．９５～２０００ｐｍｏｌ;批内变异系数分别为４．４５％和４．７９％;批间变异系数分别为１．１５％和１．５０％。笔者用这两种ＥＬＩＳＡ检测了兰花气生根和桑树苗样品中ＩＡＡ的含量,发现两种检测结果相当一致。     

Determination of unbound concentration of the novel anti-tumour agent 5,6-dimethylxanthenone-4-acetic acid in human plasma by ultrafiltration followed by high-performance liquid chromatography with fluorimetric detection

The novel anti-tumour agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) is a highly protein bound drug with narrow therapeutic window. We report a simple HPLC method with fluorimetric detection for the determination of free DMXAA concentration in human plasma. Sample preparation involves the ultrafiltration of plasma by a Centrisart device for 30 min at 2000 g and extraction with acetonitrile: methanol mixture. The method was validated with respect to recovery, selectivity, linearity, precision, and accuracy. Calibration curves for DMXAA were constructed at the concentration range of 0.5–40 μM in blank plasma and phosphate buffer. The difference between the theoretical and calculated concentration and the relative standard deviation were less than 10% at all quality control (QC) concentrations. The HPLC method has been used for the analysis of preclinical studies.     

Auxin activity and molecular structure of 2-alkylindole-3-acetic acids

2-Methylindole-3-acetic acid (2-Me-IAA) is a known auxin, but its 2-ethyl homologue has been considered inactive. Here we show that the compound previously bioassayed as 2-ethylindole-3-acetic acid (2-Et-IAA) was, in fact, 3-(3-methylindol-2-yl)propionic acid. The proper 2-Et-IAA and its 2-(n-propyl) homologue (2-Pr-IAA) are prepared, unambiguously characterized, and their auxin activity is demonstrated in the Avena coleoptile-section straight-growth test. Their half-optimal concentrations are approximately the same as for 2-Me-IAA (2 × 10^–5mol L^–1), and hence about ten times larger than for unsubstituted indole-3-acetic acid (IAA) and its derivatives alkylated in positions 4, 5, 6 or 7. The optimal response elicited by 2-Et-IAA and 2-Pr-IAA is about half that observed for 2-Me-IAA. These characteristics place the three 2-alkyl-IAAs along the borderline between the classes of strong and weak auxins, thus corroborating the results of interaction similarity analysis, a mathematical approach based on the capability of auxin molecules to participate in non-bonding interactions with a generalized receptor protein. X-ray diffraction analysis shows no explicit structural features to be blamed for the decrease in auxin activity caused by attaching a 2-alkyl substituent to the IAA molecule; sterical interference of the 3-CH₂COOH group and the 2-alkyl moiety is barely recognizable in the crystalline state. Quantum-chemical calculations and molecular dynamics simulations suggest that 2-alkyl-IAAs, in the absence of crystal-packing restraints, prefer conformations with the CH₂-COOH bond tilted to the heterocyclic ring system. Substantially higher conformational energy (and hence lower abundance) is predicted for planar conformers which were previously shown to prevail for IAA and many of its derivatives substituted in the benzene moiety of the indole nucleus. This shift in the rotational preferences of the -CH₂COOH moiety may be one of the reasons for the reduced plant-growth promoting activity of 2-alkyl-IAAs.     

Facile Preparation of Deuterium-Labeled Standards of Indole-3-Acetic Acid (IAA) and Its Metabolites to Quantitatively Analyze the Disposition of Exogenous IAA in Arabidopsis thaliana

[2′,2′-²H₂]-indole-3-acetic acid ([2′,2′-²H₂]IAA) was prepared in an easy and efficient manner involving base-catalyzed hydrogen/deuterium exchange. 1-O-([2′,2′-²H₂]-indole-3-acetyl)-β-D-glucopyranose, [2′,2′-²H₂]-2-oxoindole-3-acetic acid, and 1-O-([2′,2′-²H₂]-2-oxoindole-3-acetyl)-β-D-glucopyranose were also successfully synthesized from deuterated IAA, and effectively utilized as internal standards in the quantitative analysis of IAA and its metabolites in Arabidopsis thaliana by using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS). The use of this technique shows that these metabolites were accumulated in the roots of Arabidopsis seedlings. Dynamic changes in the metabolites of IAA were observed in response to exogenous IAA, revealing that each metabolic action was regulated differently to contribute to the IAA homeostasis in Arabidopsis.     

Longitudinal Gradients of Indole-3-Acetic Acid and Abscisic Acid in the Hypocotyl of Etiolated Bean Seedlings

The longitudinal distribution of abscisic acid (ABA) and indole-3-aceticacid (IAA) along the hypocotyl of 5-d-old etiolated Phaseolusvulgaris L. cv. Limburg seedlings was measured. IAA was analysedby the L-methyl-indole--pryone assay (2-MIP) and ABA by electroncapture gas chromatography (ECD-GC). Length and width of theinner parenchyma cells, growth rate and protein content werealso measured. Cell expansion occurred predominantly in a region20 mm below the centre of the hook where elongation rate wasmaximal and where protein concentration decreased rapidly withdistance from the hook. The ratio between ABA and IAA was constant along the lengthof the hypocotyl. On a fresh weight basis the concentrationof both growth substances was maximal in the upper (youngest)part, decreased in slightly older sections where cell expansionwas proceeding and was smallest in the basal regions where cellexpansion was complete. However, when expressed on a proteinbasis the concentration gradient of the hormones was the reverseof that described on a fresh weight basis. Key words: IAA, ABA, hypocotyl, etiolated, bean     

A high-throughput method for the quantitative analysis of indole-3-acetic acid and other auxins from plant tissue

To investigate novel pathways involved in auxin biosynthesis, transport, metabolism, and response, we have developed a high-throughput screen for indole-3-acetic acid (IAA) levels. Historically, the quantitative analysis of IAA has been a cumbersome and time-consuming process that does not lend itself to the screening of large numbers of samples. The method described here can be performed with or without an automated liquid handler and involves purification solely by solid-phase extraction in a 96-well format, allowing the analysis of up to 96 samples per day. In preparation for quantitative analysis by selected ion monitoring-gas chromatography-mass spectrometry, the carboxylic acid moiety of IAA is derivatized by methylation. The derivatization of the IAA described here was also done in a 96-well format in which up to 96 samples can be methylated at once, minimizing the handling of the toxic reagent, diazomethane. To this end, we have designed a custom diazomethane generator that can safely withstand high flow and accommodate larger volumes. The method for IAA analysis is robust and accurate over a range of plant tissue weights and can be used to screen for and quantify other indolic auxins and compounds including indole-3-butyric acid, 4-chloro-indole-3-acetic acid, and indole-3-propionic acid.     

IAA, ABA, polyamines and free amino acids associated with zygotic embryo development of Ocotea catharinensis

The aim of this work was to study morphological and biochemical aspects during zygotic embryogenesis in O. catharinensis, by measuring changes in the endogenous concentrations of proteins, amino acids, polyamines (PAs), indole-3-acetic acid (IAA) and abscisic acid (ABA). Buffer-soluble and insoluble protein contents were determined by spectrometry, and amino acids, PAs, IAA and ABA concentrations were determined by high performance liquid chromatography. Total amino acid accumulation, predominantly asparagine, occurred when the embryo showed completely developed cotyledons, with posterior reduction in the mature embryo. This decrease in total amino acid concentration in the mature embryo may result from their use in storage␣as well as for LEA protein synthesis. Free putrescine (Put) concentration decreased, while free spermine (Spm) increased during embryo development. This suggest a role for Put in the initial phases of embryogenesis when high rates of cell division occur, while elevated concentration of Spm are essential from the middle to the end of embryo development, when growth is mainly due to cell elongation. An IAA peak in zygotic embryos occurred during initial development, suggesting a link between growth and cellular division as well as with the establishment of bilateral symmetry. ABA concentration declined during initial stages of development then increased at the mature embryo stage, suggesting a possible relationship with dormancy and recalcitrance characteristics. Our results show that changes in the phytohormones (IAA, ABA and PAs) concentrations in combination with amino acids are likely important factors determining the developmental stages of O.␣catharinensis zygotic embryos.     

Phytohormones in needles of healthy and declining silver fir (Abies alba Mill.): I. Indole-3-acetic acid

 Levels of indole-3-acetic acid (IAA) were determined in needles from silver fir (Abies alba Mill.) trees in the northern Black Forest. IAA was quantified by gas chromatography (GC) as 1-heptafluorobutyryl-IAA-methylester (HFB-IAA-ME) using electron capture detection. Prior to GC analysis, extensive purification of needle extracts was performed employing two HPLC steps. Peak identity of HFB-IAA-ME was confirmed by combined gas chromatography-mass spectrometry in selected samples. Levels of IAA in needles belonging to different needle age-classes exhibited a cyclic seasonal pattern with highest concentrations in winter and lowest levels in spring when bud-break occurred. Such a cyclic seasonal pattern of IAA levels was also observed in needles from declining fir trees or fir trees suffering from a strong sulfur impact (S-impact) in the field due to a local SO₂ source. Levels of IAA increased with increasing needle age. This age dependency of IAA concentrations was most pronounced in late autumn when IAA levels were high and nearly disappeared in spring when IAA levels reached their minimum. In needles from declining fir trees or fir trees suffering from a strong S-impact in the field, IAA levels hardly increased with increasing needle age. It is suggested that in healthy trees high levels of IAA protect older needles from abscission and that the considerable losses of older needles of declining fir trees or of fir trees under S-impact are a consequence of the low levels of IAA found in older needles of such trees. Received: 4 May 1995 / Accepted: 29 August 1995     

高效液相色谱法同时测定银凤桃中的赤霉素和脱落酸

赤霉素(GA3)和脱落酸(ABA)是果实组织中的两个重要激素,本试验用SymmetryC18色谱柱(4.6mm×150mm),以乙腈和1.8%乙酸[V(CH3CN)∶V(1.8%CH3COOH)=1∶1]为流动相,流速为0.5mL·min-1,Wa-ters2487UV-检测器,在检测波长254nm,柱温25℃的条件下,同时分离并测定了银凤桃中的GA3和ABA。GA3和ABA的分离效果理想,回收率分别达到100.1%和99.8%,该方法测量灵敏度达10-2ng·g-1,精密度RSD%<0.1。     

Abscisic acid and indole-3-acetic acid contents in orange trees infected by Xylella fastidiosa and submitted to cycles of water stress

Pêra sweet orange plants (Citrus sinensis L. Osbeck) grafted on Rangpur lime rootstock (1 year-old) (Citrus limonia Osbeck) were inoculated with Xylella fastidiosa, a xylem-limited bacterium pathogen, which causes Citrus Variegated Chlorosis (CVC). Since it was known that water deficiency in the field enhances CVC-effects on the plant, the trees were submitted to three cycles of water stress during a one year period (March and October, 1998; and April, 1999) and divided in four treatments: healthy plants (HP); water-stressed healthy plants (WSHP); diseased plants (DP) and water-stressed diseased plants (WSDP). Stomatal conductance (g _s) of water-stressed diseased plants decreased in the first and second cycles of water deficiency, as the stress was increasing. The low stomatal conductance verified may be due to the high concentrations of abscisic acid (ABA) found in these plants. In the third cycle, values of g _s in diseased plants were, usually, lower than in the healthy ones. In healthy plants, g _s was reduced when these plants were submitted to water deficiency, independently of the cycle. The drop in leaf water potential in healthy plants was faster after irrigation was withheld, because healthy plants transpired more and, therefore, the water content of the substrate decreased more quickly. When the irrigation of WSDP was withheld in the third cycle, it was not possible to detect increases in ABA contents, suggesting that other factors could be acting to diminish the stomatal conductance in these plants. The presence of Xylella fastidiosa did not induce an increase in indole-3-acetic acid content in the leaves. After three cycles of water deficiency, the concentrations of indole-3-acetic acid in WSHP and WSDP were lower than those concentrations in the irrigated controls on the day water stress was more severe.     

Modified solvent partitioning scheme providing increased specificity and rapidity of immunoassay for indole-3-acetic acid

Based on the distribution constant of IAA, the efficiency of solvent partitioning has been improved by modifying the proportions of the solvents. IAA is recovered almost quantitatively by this method which also renders further sample reduction superfluous. Selective IAA recovery is supported by the distribution of immunoreactive materials on chromatograms. This modified scheme simplifies prepurification of samples for more reliable immunoassay.     

Hormones in zygotic and microspore embryos of Brassica napus

A number of studies have used microspore-derived embryos (MDEs) as amodel for examining a range of processes, including hormonal regulation ofembryo development. We examined the hormonal physiology of MDEs with theprimaryobjective of testing the validity of using the MDE system as a model forhormonally-regulated development in zygotic embryos, through late stages. To dothis we identified and quantified endogenous levels of abscisic acid (ABA),indole-3-acetic acid (IAA) and a number of gibberellins (GAs), includingGA₁₉, GA₂₀, GA₁ and GA₈ in bothMDEsand zygotic embryos. The presence of GA₁₉, together with itsC₁₉ metabolites indicates that the early-13 hydroxylation pathway isoperative in both embryo systems. Gibberellins A₄ and GA₉were also identified, thereby confirming the presence of the earlynon-hydroxylation pathway in B. napus MDEs and zygoticembryos. In general, the pattern of change of hormone (ABA, IAA, GA₁and GA₂₀) content per embryo through embryogenesis was similar forMDEs and zygotic embryos. Indole-3-acetic acid and GA₁ increased toamaximum at day 30 after culture (DAC) before decreasing. Abscisicacid levels increased to a maximum at day 35, and declined in zygoticembryos but not in MDEs. GA₂₀ increased to the final harvest atmaturity, or day 40. The absolute content (g/embryo) of each hormone, howeverwas appreciably lower (5- to 15- fold) in the MDEs. This was not the result ofdilution into surrounding medium for ABA or IAA; GA₁, however, didaccumulate in the medium. Although there were absolute quantitative differencesin the levels of IAA and ABA found in the two embryo systems, the similaritiesin the pattern of hormone changes suggests that the MDE system can serve as auseful model for examining the physiological roles of hormones duringembryogenesis.