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1.
M. G. Mina  A. Goldsworthy 《Planta》1991,186(1):104-108
Weak externally applied electric currents changed the natural electrical pattern surrounding cells from tobacco (Nicotiana tabacum L.) suspension cultures. The artificial currents were applied transversely to short filaments of cells placed between a microelectrode lose to the filament surface and a large platinum electrode some distance away. The natural current patterns before and after electrical treatment were measured with a vibrating probe. Significant effects were confined to the cell adjacent to the microelectrode. Currents with densities of 100 A · cm–2 at the cell surface applied for 10 min or 3 A · cm–2 for several hours caused a localized increase in the natural current entering the part of the cell which had been nearest the positive electrode. There was no corresponding local increase in current leaving from the opposite side of the cell. Instead, the extra current appeared to leave over a relatively large area. The overall effect was a tendency for the cell to repolarize transversely with a greater proportion of its transcellular currents flowing in the direction of the current applied. The effect was measurable for several hours after the external current was discontinued and may be evidence for a natural mechanism by which neighbouring cells entrain one another's polarities during differentiation. The effect of external currents on cells growing in a 2,4-dichlorophenoxyacetic acid (2,4-D) medium (which suppresses differentiation) was qualitatively the same as on cells in an indole-3-acetic acid medium (which promotes differentiation). If anything, the response was greater in 2,4-D, implying that the disruptive effect of 2,4-D on cell and tissue polarization is not a consequence of it preventing cells sensing the transcellular currents of their neighbours.Abbreviation 2,4-D 2,4-dichlorophenoxyacetic acid The authors are indebted to the Agricultural and Food Research Council of the U.K. for financial support and to the Royal Society for the provision of the vibrating probe.  相似文献   

2.
Accumulation of radiolabelled naphthalene-1-acetic acid (1-NAA), 2,4-dichlorophenoxyacetic acid (2,4-D), and indole-3-acetic acid (IAA) has been measured in suspension-cultured tobacco (Nicotiana tabacum) cells. In this paper is presented a simple methodology allowing activities of the auxin influx and efflux carriers to be monitored independently by measuring the cellular accumulation of [3H]NAA and [14C]2,4-D. We have shown that 1-NAA enters cells by passive diffusion and has its accumulation level controlled by the efflux carrier. By contrast, 2,4-D uptake is mostly ensured by the influx carrier and this auxin is not secreted by the efflux carrier. Both auxin carriers contribute to IAA accumulation. The kinetic parameters and specificity of each carrier have been determined and new information concerning interactions with naphthylphthalamic acid, pyrenoylbenzoic acid, and naphthalene-2-acetic acid are provided. The relative contributions of diffusion and carrier-mediated influx and efflux to the membrane transport of 2,4-D, 1-NAA, and IAA have been quantified, and the data indicate that plant cells are able to modulate over a large range their auxin content by modifying the activity of each carrier.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - 1-NAA naphthalene-1-acetic acid - 2-NAA naphthalene-2-acetic acid - NPA N-1-naphthylphthalamic acid - PBA 2-(1-pyrenoyl)benzoic acid - Vm maximum transport capacity of the carrier In honour of Professor Dieter Klämbt's 65th birthdayThe authors thank Drs. A.E. Geissler and G.F. Katekar (CSIRO, Canberra City, Australia) for providing auxin efflux carrier inhibitors CPD, CPP, and PBA, and Dr. H. Barbier-Brygoo (Institut des Sciences Végétales, CNRS, Gif-sur-Yvette, France) for helpful discussions. This work was supported by funds from the Centre National de la Recherche Scientifique (UPR0040).  相似文献   

3.
4.
The accumulation and decline of free indole-3-acetic acid (IAA) and tryptophan has been monitored in cells of Acer pseudoplatanus L. grown in batch suspension cultures. The period of maximal IAA accumulation per cell or per unit dry weight of tissue was found to precede the peak of tryptophan accumulation by several days. A study of cell viability throughout a growth passage indicated the presence of a basal level of non-viable cells of 5–7%, with only minor increases occurring during the first week of the three-week growth passage. The results suggest that IAA biosynthesis is not regulated by substrate availability arising from proteolysis in dead cells.Abbreviation GC-MS Gas chromatography-mass spectrometry - IAA indole-3-acetic acid - 5-MT 5-methyltryptophan - TLC thin-layer chromatography  相似文献   

5.
The compartmentation and metabolism of indole-3-acetic acid (IAA) was examined in protoplasts derived from needles ofPinus sylvestris L., leaves of normal plants ofNicotiana tabacum L., leaves ofN. tabacum plants carrying the T-DNA gene 1 (rG1 plants) and leaves ofN. tabacum plants carrying the T-DNA gene 2 (rG2 plants) by using a rapid cell-fractionation method. In all tissues, 30%–40% of the IAA pool was located in the chloroplast, while the remainder was found in the cytosol. Quantitative analysis of indole-3-ethanol (IEt) showed that in bothPinus andNicotiana the IEt pool was located exclusively in the cytosol. The only plant that contained endogenous indoleacetamide (IAAm) was therG1-mutant ofN. tabacum, expressing theAgrobacterium tumefaciens T-DNA gene 1. Cellular fractionation of protoplasts from this transgenic plant showed that the entire IAAm pool was located in the cytosol. Feeding experiments utilizing [5-3H]tryptophan, [5-3H]IEt, [1′-14C] and [2′-14C]IAA demonstrated that the biosynthesis and catabolism of IAA occurred in the cytosol in bothPinus and in the wild type and the different mutants ofNicotiana. Furthermore, the biosynthesis of IAAm in therG1 plants was also shown to be localized in the cytosol.  相似文献   

6.
We have developed a specific radioimmunoassay [RIA] for indole-3-acetic acid (IAA) in the 0.2 ng to 12 ng range which, in principle, can be extended to other indole auxins as well. Methods are presented for obtaining suitable antibody, for the RIA procedure, and for measuring IAA in methanolic extracts of plant tissues. Antibody specific for IAA was obtained from rabbits immunized with IAA bound to bovine serum albumin by formaldehyde treatment. In assays with this antibody, 2,4-dichlorophenoxyacetic acid and indoles structurally related to IAA reacted from 300- to 3000-fold less than did IAA itself. However, -and -naphthaleneacetic acid reacted significantly and hence interfered with the assay. Extracts of tobacco (Nicotiana tabacum L.) tissue were immunoassayed after partial purification by buffer-ether partition. Crown-gall tumor tissue, which is auxin-autotrophic, and pith tissue depleted of auxin by the diffusion method contained, respectively, 26.7 ng and <0.5 ng extractable IAA per gram fresh weight.Abbreviations BSA bovine serum albumin - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - -NAA -naphthalenacetic acid - PBS phosphate-buffered saline - RIA radioimmunoassay  相似文献   

7.
Göran Sandberg 《Planta》1984,161(5):398-403
Combined gas chromatography-mass spectrometry has been used to identify indole-3-ethanol (IEt) in a purified extract from needles of Pinus sylvestris L. Quantitative estimates obtained by high-performance liquid chromatography with fluorescence detection, corrected for samples losses occurring during purification, indicate that Pinus needles contain 46±4 ng g-1 IEt. This compares with 24.5±6.5 ng g-1 indole-3-acetic acid (IAA) and 2.3±0.4 ng g-1 indole-3-carboxylic acid (ICA) (Sandberg et al. 1984, Phytochemistry, 23, 99–102). Metabolism studies with needles incubated in a culture medium in darkness revealed that both [3-14C]-tryptophan and [2-14C]tryptamine mine are converted to [14C]IEt. It was also shown that [3-14C]IEt acted as a precursor of [14C]IAA. The observed metabolism appears to be enzymic in nature. The [2-14C]IAA was not catabolised to [14C]ICA in detectable quantities implying that, at best, only a minor portion of the endogenous ICA pool in the Pinus needles originates from IAA.Abbreviations DEAE diethylaminoethyl - GC-MS gas chromatography-mass spectrometry - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - ICA indole-3-carboxylic acid - IEt indole-3-ethanol - PVP polyvinylpyrrolidone  相似文献   

8.
Indole-3-acetic acid (IAA) was oxidized by horseradish peroxidase, but ester and amide conjugates of IAA were not degraded. Addition of indoleacetyl-myo-inositol, indoleacetyl-L-aspartate, indoleacetylglycine, indoleacetyl-L-alanine, indoleacetyl-D-alanine, or indoleacetyl--alanine did not affect the rate of oxidation of IAA by horseradish peroxidase. Peroxidase preparations from Pisum sativum L. and Zea mays L. behaved similarly in that they rapidly oxidized IAA, but not conjugates found in the plant from which the peroxidase was prepared. These results indicate that conjugation could affect the stability of IAA in vivo.Abbreviation IAA Indole-3-acetic acid  相似文献   

9.
Synthesis of indole-3-acetic acid (IAA), using stable-isotope incorporation, was investigated in Zea mays L. Incorporation of 2H from 2H2O into IAA molecules was shown to occur in intact plantlets and excised primary roots cultured in vitro. This demonstrates the de-novo formation of IAA, a process which is quantitatively well defined and is initiated early in germination.Abbreviations IAA indole-3-acetic acid  相似文献   

10.
It has been reported that auxin induces an epinastic growth response in plant leaf tissues. Leaf strips of tobacco (Nicotiana tabacum L. 'Bright Yellow 2') were used to study the effects of indole-3-acetic acid (IAA), the principal form of auxin in higher plants, and a synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), on epinastic leaf curvature. Incubation of leaf strips with 10 micro M IAA resulted in a marked epinastic curvature response. Unexpectedly, 2,4-D showed only a weak IAA-like activity in inducing epinasty. Interestingly, the presence of 2,4-D resulted in inhibition of the IAA-dependent epinastic curvature. In vivo Lineweaver-Burk kinetic analysis clearly indicated that the interaction between IAA and 2,4-D reported here is not a result of competitive inhibition. Using kinetic analysis, it was not possible to determine whether the mode of interaction between IAA and 2,4-D was non-competitive or uncompetitive. 2,4-D inhibits the IAA-dependent epinasty via complex and as yet unidentified mechanisms.  相似文献   

11.
Z. R. Sung 《Planta》1979,145(4):339-345
A 5-methyltryptophan(5-MT)-resistant cell line of wild carrot (Daucus carota L.), W001, that exhibited auxin-independent callus growth, was found to accumulate indole-3-acetic acid (IAA) and tryptophan (trp). Anthranilate-synthetase activity in W001 cell extract was less sensitive to feedback inhibition by trp than in the original 5-MT-sensitive cell lines. It is hypothesized that the resistant enzyme allowed more trp synthesis and accumulation which, in turn, affected the IAA concentration in the cell. Since carrot cultures cannot regenerate in the presence of exogenous auxin, the elevated IAA concentration in W001 may be responsible for its drastically reduced capacity to regenerate. The relationship between trp and IAA levels was further investigated by examining the effect of 2,4-dichlorophenoxy acetic acid (2,4-D) on the endogenous concentration of trp and IAA. In general, the IAA level was reduced but the trp concentration was elevated when 2,4-D was present in the culture medium.Abbreviations 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - 5-MT 5-methyltryptophan - 5-MTr 5-MT-resistant - 5-MTs 5-MT-sensitive - trp tryptophan  相似文献   

12.
The use of spectrofluorimeter coupled to a reverse phase high performance liquid chromatography column permits selective detection of indole-3-acetic acid at the low picogram level. The value of the technique is demonstrated by the analysis of endogenous IAA in elongating shoots, xylem sap and callus of Douglas-fir. The data are also used to illustrate a procedure whereby the accuracy of chromatographic analyses can be verified within definable probability limits.Abbreviations GC-MS combined gas chromatography-mass spectrometry - HPLC high performance liquid chromatography - IAA indole-3-acetic acid - SEC steric exclusion chromatography - SICM selected ion current monitoring Technical Paper No. 5379 from the Oregon State University Agricultural Experiment Station  相似文献   

13.
Oxindole-3-acetic acid (OxIAA) has been identified in germinating seeds of Scots pine (Pinus sylvestris) using gas chromatography-mass spectrometry. Seeds germinated for 5 d contained 2.7 ng OxIAA·g-1 (dry weight) whereas ungerminated seeds contained 0.2 ng·g-1. Isotopically labelled OxIAA was formed in seeds incubated with [1-14C]-, [2-14C]- or [2H5]indole-3-acetic acid.Abbreviations DDC sodium diethyldithiocarbamate - GC gas chromatography - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - MS mass spectrometry - OxIAA oxindole-3-acetic acid - PVP polyvinylpyrrolidone - TMS trimethylsilyl  相似文献   

14.
Gas chromatography-mass spectrometric analyses of purified extracts from cultures of Rhizobium phaseoli wild-type strain 8002, grown in a non-tryptophan-supplemented liquid medium, demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol (IEt), indole-3-aldehyde and indole-3-methanol (IM). In metabolism studies with 3H-, 14C- and 2H-labelled substrates the bacterium was shown to convert tryptophan to IEt, IAA and IM; IEt to IAA and IM; and IAA to IM. Indole-3-acetamide (IAAm) could not be detected as either an endogenous constituent or a metabolite of [3H]tryptophan nor did cultures convert [14C]IAAm to IAA. Biosynthesis of IAA in R. phaseoli, thus, involves a different pathway from that operating in Pseudomonas savastanio and Agrobacterium tumefaciens-induced crown-gall tumours.Abbreviations IAA indole-3-acetic acid - IAld indole-3-aldehyde - IAAm indole-3-acetamide - IEt indole-3-ethanol - IM indole-3-methanol - HPLC-RC high-performance liquid chromatography-radio counting - GC-MS gas chromatography-mass spectrometry  相似文献   

15.
P. E. Pilet  P. Meuwly 《Planta》1986,169(1):16-22
Five types of anion-exchanger resin beads which had adsorbed indole-3-acetic acid (IAA) were tested as IAA donors. The rate of IAA-uptake by beads was a function of time and pH. The release was relatively steady during 6 h application on vertical maize roots. No IAA degradation occurred in the beads (Amberlite IRA 400 type) but 45.8% was metabolised in the roots during treatment. Beads loaded with IAA and placed on one side of the root (at 2.20±0.03 mm from the tip) induced a curvature towards and above the bead (23.3±1.1 degrees after 5.25 h application). In contrast, control beads (without IAA) did not change the axial growth rate. Applied IAA seemed to move differently from endogenous IAA. The use of resin beads loaded with IAA offers a technique to study the effects of local IAA application on intact growing roots.Abbreviations 3,3-DGA 3,3 dimethyl-glutaric acid - HPLC high-performance liquid chromatography - IAA indole-3-acetic acid - Ox-IAA oxindole-3-acetic acid  相似文献   

16.
When cell-suspension cultures and callus tissue from Nicotiana tabacum are grown on medium containing -naphthaleneacetic acid (NAA) and kinetin, three classes of auxin-binding proteins can be detected. When the herbicide 2,4-dichlorophenoxyacetic acid is used instead of both NAA and kinetin, one of these sites, which is membranebound, disappears. After retransferring cells to medium containing NAA and kinetin, this membrane-bound site reappears after four to eight weeks. This reappearance is correlated with the ability of the cells to regenerate roots.Abbreviations IAA indole-3-acetic acid - NAA -naphthaleneacetic acid - 2,4-D 2,4-dichlorophenoxyacetic acid  相似文献   

17.
Root segments of Pisum sativum L. were transformed by several strains of Agrobacterium rhizogenes. The resulting hairy roots, as well as apical segments from untransformed pea roots, were used to initiate root lines cultured in vitro. Levels of free IAA were quantified in the sub-cultured lines by gas-chromatography coupled to mass spectrometry, using selected ion monitoring. For most of the cultured untransformed and transformed root lines the IAA content was very small, compared with levels in untransformed intact primary roots. However, an agropine-type hairy root line (incited by strain 15834) contained significantly higher amounts of IAA. The peculiar phenotype of this root line (abundant production of calli) appears to be associated with an increased IAA level, as opposed to most of the hairy root lines, where the extensive secondary root proliferation associated with the hairy-root disease cannot be merely attributed to a markedly enhanced IAA content.  相似文献   

18.
S. Lachaud  J. L. Bonnemain 《Planta》1984,161(3):207-215
Branches were cut from young beeches (Fagus sylvatica L.) at various stages of the annual cycle and [3H]indole-3-acetic acid (0.35 nmol) was applied to the whole surface of the apical section of each branch, just below the apical bud. The labelled pulse (moving auxin) and the following weakly radioactive zone (auxin and metabolites retained by the tissues) were localized by counting: microautoradiographss were made using cross sections from these two regions. During the second fortnight of April, auxin was transported by nearly all the cells of the young primary shoot, but the label was more concentrated in the vascular bundles. Auxin transport became the more localized: the cortical parenchyma appeared to lose its ability to transport the hormone (end of April), followed in turn by the pith parenchyma (May). Polar auxin movement at that time was limited to the outer part of the bundle (cambial zone and phloem) and to the inner part (protoxylem parenchyma). Later protoxylem parenchyma ceased to carry auxin. During the whole period of cambial activity, auxin was transported and retained mainly by the cambial zone and its recent derivatives. In September, before the onset of dormancy, and in February, at the end of the resting period, the transport pathways and retention sites for auxin were mainly in the phloem, where sieve tubes often completely lacked radiolabel. When cambial reactivation occurred in the one-year shoot, auxin was mainly carried and retained again in the cambial zone and differentiating derivatives.Abbreviation IAA indole-3-acetic acid  相似文献   

19.
Germinating seed ofDalbergia dolichopetala converted both [2H5]l-tryptophan and [2H5]indole-3-ethanol to [2H5]indole-3-acetic acid (IAA). Metabolism of [2-14C]IAA resulted in the production of indole-3-acetylaspartic acid (IAAsp), as well as several unidentified components, referred to as metabolites I, II, IV and V. Re-application of [14C]IAAsp to the germinating seed led to the accumulation of the polar, water-soluble compound, metabolite V, as the major metabolite, together with a small amount of IAA. Metabolites I, II and IV were not detected, nor were these compounds associated with the metabolism of [2-14C]IAA by shoots and excised cotyledons and roots from 26-d-oldD. dolichopetala seedlings. Both shoots and cotyledons converted IAA to IAAsp and metabolite V, while IAAsp was the only metabolite detected in extracts from excised roots. The available evidence indicates that inDalbergia, and other species, IAAsp may not act as a storage product that can be hydrolysed to provide the plant with a ready supply of IAA.Abbreviations HPLC-RC high-performance liquid chromatography-radiocounting - IAA indole-3-acetic acid - IAAsp indole-3-acetylaspartic acid - IAlnos 2-O-indole-3-acetyl-myo-inositol - IEt indole-3-ethanol  相似文献   

20.
A specific solid-phase enzyme immunoassay for the detection of as little as 3–4 pg of indole-3-acetic acid (IAA) is described. The assay involves minimal procedural efforts and requires only standard laboratory equipment. Up to 50 samples in triplicate, processed simultaneously, can be assayed and evaluated in 2.5 h. As little as 1 mg oat coleoptile tissue is sufficient for a quantitative IAA analysis and little or no extract purification is necessary. Using this assay, levels of IAA have been determined in coleoptiles of maize and oat. The distribution of IAA within single coleoptiles was quantitated and the production of IAA during the regeneration of the physiological tip in Avena coleoptiles was investigated. The changes in levels of IAA and other major phytohormones were quantitated during the growth of oat coleoptiles.Abbreviations ABA abscisic acid - BHT butylated hydroxytoluene - BSA bovine serum albumin - IAA indole-3-acetic acid - TBS Trishydroxymethylaminomethane buffered saline Part 21 in the series Use of Immunoassay in Plant Science  相似文献   

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