Showing papers on "Zeatin published in 1985"
TL;DR: There are at least two phases in the differentiation of embryos from single cells, and the progression of the first phase required exogenous auxin, whereas that of the second phase was inhibited by the same growth regulator.
Abstract: A system was established in which single cells differentiated to embryos at a high frequency. Small spherical single cells from a carrot (Daucus carota L. cv “Kurodagosun”) cell suspension culture were obtained by fractionation through sieving, using nylon screens and then density gradient centrifugation in Percoll solutions. Eighty-five to 90% of these small single cells differentiated to embryos when they were cultured in a medium containing 2,4-dichlorophenoxyacetic acid (5 × 10−8 molar), zeatin (10−6 molar), and mannitol (0.2 molar) for 7 days, followed by transfer to a medium containing zeatin (10−7 molar) but no auxin. This indicates that there are at least two phases in the differentiation of embryos from single cells. The progression of the first phase required exogenous auxin, whereas that of the second phase was inhibited by the same growth regulator. The relationship between the morphology and potency for embryogenesis from single cells was discussed. The system established here is a useful one for investigation of differentiation process from a single cell to a whole plant via embryogenesis, especially in its early stage.
224 citations
TL;DR: Seaweed concentrate prepared from Ecklonia maxima stimulated the growth of in vitro cultured tomato roots and both root extension and root elongation were significantly improved, indicating the presence of more than one stimulatory compound each which may affect different aspects of root growth differently.
145 citations
TL;DR: The metabolism of trans-[8-(14)C]zeatin was examined in embryos of Phaseolus vulgaris and P. lunatus in an attempt to detect genetic variations in organized plant tissues, and genetic differences appear to be embryo-specific.
Abstract: The metabolism of trans-[8-14C]zeatin was examined in embryos of Phaseolus vulgaris cv Great Northern (GN) and P. lunatus cv Kingston (K) in an attempt to detect genetic variations in organized plant tissues. Metabolites were fractionated by HPLC, and identified by chemical and enzymic tests and GC-MS analyses. Five major metabolites were recovered from P. vulgaris embryo extracts: ribosylzeatin, ribosylzeatin 5′-monophosphate, an O-glucoside of ribosylzeatin, and two novel metabolites, designated as I and II. Based on results of degradation tests and GC-MS analyses, I and II were tentatively identified as O-ribosyl derivatives of zeatin and ribosylzeatin. In embryos of P. lunatus, however, metabolites I and II were not present. The major metabolites were ribosylzeatin, ribosylzeatin 5′-monophosphate, and the O-glucosyl derivatives of zeatin and ribosylzeatin. The zeatin metabolites recovered were the same for embryos of different sizes but their quantities varied with embryo size and incubation time. The genetic differences appear to be embryo-specific and may be useful in the studies of the possible relationship between abnormal interspecific hybrid embryo growth and hormonal derangement in Phaseolus. In addition, analyses of both organized (intact) and unorganized (callus) tissues of the same genotype may provide an opportunity to address the problem of differential expression of genes regulating cytokinin metabolism during plant development.
66 citations
TL;DR: A radioimmunoassay, combined with high-performance liquid chromatography, has been used to analyse the zeatin-type cytokinins of potato tubers and tuber buds throughout growth and storage, finding that metabolism of injected cytokinin was greater in non-dormant than in dormant tubers.
Abstract: A radioimmunoassay, combined with high-performance liquid chromatography, has been used to analyse the zeatin-type cytokinins of potato (Solanum tuberosum L. cv. Majestic) tubers and tuber buds throughout growth and storage. During tuber growth, zeatin riboside was the predominant cytokinin detected in all tissues. Immediately after harvest, the total cytokinin concentration fell dramatically in the storage tissue, largely as a consequence of the disappearance of zeatin riboside. During storage, levels of cytokinins in the storage tissue remained relatively constant, but increased in the tuber buds. In the buds of tubers stored at 2°C there was a 20-to 50-fold increase in total cytokinin over six weeks, coinciding with the natural break of innate dormancy. At 10°C the rise in the level of bud cytokinins was slower, correlating with the longer duration of innate dormancy. Injecting unlabelled cytokinins into tubers in amounts known to induce sprouting gave rise to increases in cytokinin concentrations in the buds of the same order as the increase associated with the natural break of dormancy. Metabolism of injected cytokinins was greater in non-dormant than in dormant tubers. The roles of cytokinin concentration and the sensitivity of the buds to cytokinin in the control of dormancy are discussed.
61 citations
TL;DR: A sub-culturable callus line was obtained from young leaf blades of Betula pendula f.
60 citations
TL;DR: Potato Line Mb1501B is a derivative of the cultivar Maris Bard (Solanum tuberosum), transformed with T-DNA from A. tumefaciens strain LBA1501, which grew as frequently branching stunted shoots with a basal callus, lacking roots.
Abstract: Potato Line Mb1501B is a derivative of the cultivar Maris Bard (Solanum tuberosum), transformed with T-DNA from A. tumefaciens strain LBA1501. In culture it grew as frequently branching stunted shoots with a basal callus, lacking roots. These shoots did not form tubers. When grafted, Mb1501B shoots gradually became morphologically more normal and aerial tubers formed readily. Cultured Mb1501B shoots contained 100–200-fold higher concentrations of the biologically-active cytokinins zeatin, zeatin riboside and their corresponding side-chain o-glucosides than untransformed Maris Bard shoots. Cultured Mb1501B shoots contained approximately a 3-fold lower concentration of indole acetic acid (IAA). In grafted Mb1501B plants a 3–10-fold higher concentration of the active cytokinins was found compared with untransformed plants and no difference in IAA concentration.
50 citations
TL;DR: It was inferred from the results that sucrose was exhausted at a low concentration of sucrose and at a high cell density, resulting in the decrease of yield of anthocyanin.
Abstract: Anthocyanin formation in a suspension culture of Daucus carota is induced by transfer from medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) to one lacking 2,4-D. The specific yields were strongly influenced by the inoculum density. Inoculum density altered the effect of zeatin concentration on anthocyanin accumulation. The in part by increasing the sucrose levels. It was inferred from the results that sucrose was exhausted at a low concentration of sucrose and at a high cell density, resulting in the decrease of yield of anthocyanin.
48 citations
TL;DR: Seven monoclonal anti-zeatin riboside antibodies were characterized by radioimmunoassay (RIA) and found to measure femtomole quantities of this cytokinin and it was possible to combine selected antibodies to provide a mixture with a predictable measuring range and cross-reactivity.
Abstract: Seven monoclonal anti-zeatin riboside antibodies were characterized by radioimmunoassay (RIA) and found to measure femtomole (10−15 M) quantities (∼20 pg) of this cytokinin. The antibodies had different measuring ranges defined by the linear portion of the logit/log plots; slopes and intercepts of the line varied considerably between the antibodies. Competitive binding trials againstcis-zeatin riboside (cZR), dihydrozeatin riboside (diHZR), zeatin (Z), and isopentenyl adenosine (iPA) showed differences among the seven antibodies in their cross-reactivities towards these structurally related cytokinins. It was possible to combine selected antibodies to provide a mixture with a predictable measuring range and cross-reactivity; the ability to prepare a highly specific reagent in this manner with well-defined reactivity was noted and differences between monoclonal antibody and polyclonal antiserum probes for measurement of cytokinins were discussed.
48 citations
TL;DR: The kinetics of growth and RA production suggested that the increase in final RA content was due to both an increase in the rate of RA synthesis and initiation of the period of synthesis in the exponential rather than the linear growth phase.
Abstract: Cell suspension cultures of Anchusa officinalis required exogenous phytohormones for their normal growth. Cell lysis was observed at the third passage in a hormone-free medium. Using hormone — depleted cells, the effects of auxins (2,4-D, NAA, IAA and CFP) and cytokinins (BA, kinetin, and zeatin) on cell growth and RA production were investigated. All auxins tested could maintain growth and integrity of the cells whereas cytokinins alone could not, suggesting that this culture is auxindependent. Among the auxins tested, NAA had a pronounced effect on RA production. The total RA content obtained at optimum NAA concentration (0.25 mg/l) reached 1.7 g/l (12% of dry weight). The kinetics of growth and RA production suggested that the increase in final RA content was due to both an increase in the rate of RA synthesis and initiation of the period of synthesis in the exponential rather than the linear growth phase.
42 citations
TL;DR: The principal biologically active cytokinins in xylem exudate of young Phaseolus vulgaris L. plants were identified by bioassay, high-performance liquid chromatography, enzymic degradation and combined gas chromatography-mass spectrometry.
Abstract: The principal biologically active cytokinins in xylem exudate of young Phaseolus vulgaris L. plants were identified by bioassay, high-performance liquid chromatography, enzymic degradation and combined gas chromatography-mass spectrometry (selected ion monitoring) a zeatin riboside, zeatin nucleotide, dihydrozeatin riboside, dihydrozeatin nucleotide, O-glucosyl zeatin, O-glycosyl dihydrozeatin, O-glucosyl dihydrozeatin riboside, and O-glucosyl dihydrozeatin nucleotide. Trace amounts of O-glucosyl zeatin riboside and O-glucosyl zeatin nucleotide were also detected.
42 citations
TL;DR: In this paper, the metabolism of N 6 -(Δ 2 -isopentenyl) adenine, dihydrozeatin, zeatin- O -glucoside and dihydrogen hydroxide was studied using derooted radish seedlings.
TL;DR: Fully habituated tissues, which are not transformed by the tumour-inducing (Ti) plasmid, contain high levels of ZR and IPA, indicating that the production of these cytokinins is not a unique property of crown-gall cells.
TL;DR: Kinetic studies of formation of glucosides of 6-benzylaminopurine in excised radish cotyledons indicated that the 3, 7, and 9-glucosides were each formed directly from BAP.
Abstract: Kinetic studies of formation of glucosides of 6-benzylaminopurine (BAP) in excised radish cotyledons indicated that the 3-, 7-, and 9-glucosides (N-glucosides) were each formed directly from BAP. The 7- and 9-glucosides of BAP and the 7-glucoside of zeatin exhibited great stability in the cotyledons, but the 3-glucoside was converted to free BAP and to the 7- and 9-glucosides of BAP. When3H-labeled zeatin was supplied to developed cotyledons, at high concentrations (100 μM), 7-glucosylzeatin was the principal metabolite, but an appreciable proportion of the extracted3H was due to O-glucosylzeatin. In immature cotyledons, as used in the radish cotyledon cytokinin bioassay, this O-glucoside was shown to be converted into zeatin 7-glucoside probably via free zeatin. Metabolism of BAP and zeatin in radish cotyledons was studied in relation to cytokinin-induced cotyledon expansion. Cytokinin N-glucosides were not metabolites responsible for the observed cytokinin-induced expansion, and were not detoxification products, or deactivation products formation of which was coupled with cytokinin action. However, the free base, its riboside, and nucleotide were possible active forms of BAP associated with cotyledon expansion. The possible significance of cytokinin N-glucosides is discussed. Senescent and nonsenescent cotyledons differed in their metabolism of BAP, zeatin, and zeatin riboside. Senescence was associated principally with a reduction in ability to form 7-glucosylzeatin, enhanced metabolism to adenine derivatives, and an inability to form appreciable amounts of 3-glucosyl-BAP. A two-dimensional thin layer chromatography (TLC) system, based on adjoining layers of cellulose and silica gel, for separating zeatin metabolites is described. This does not completely separate zeatin and zeatin riboside from the corresponding dihydro-compounds. A reversed phase TLC method for achieving these separations is also reported.
TL;DR: In this article, the change in the levels of endogenous cytokinins in the shoot and grain of rice (Oryza sativa L. japonica cultivar Nihonbare) during its growth and development was followed by selected ion monitoring using deuterium-labeled internal standards.
Abstract: The change in the levels of endogenous cytokinins in the shoot and grain of rice (Oryza sativa L. japonica cultivar Nihonbare) during its growth and development was followed by selected ion monitoring using deuterium-labelled internal standards. Five cytokinins, zeatin (Z), cis-Z, ribosyl-zeatin (RZ), cis-RZ and 6-(3-methyl-but-2-enylamino)purine riboside were detected in the shoot, root and ear of rice. The maximum contents of RZ and Z in the shoot and root were found at the maximum tillering stage. In the ear, the levels of Z and RZ changed markedly. It is therefore suspected that RZ and Z play some roles in the tillering and seed growth in rice.
TL;DR: The regeneration capacity of calli decreased gradually and ended after 6 months in culture, and a low percentage of albino plants was observed among the regenerated plants.
Abstract: Callus cultures were initiated from isolated immature embryos of Hordeum spontaneum and Hordeum bulbosum on MS or B5 basal medium supplemented with 2 mg/1 2,4-D. Shoot regeneration occurred on transfer of tissue to media containing 1 mg/1 IAA and 1 mg/1 zeatin. The regenerated shoot buds were rooted on basal medium without hormones. The in vitro regenerated plants were transferred to soil and were grown to fertile mature plants. A low percentage of albino plants was observed among the regenerated plants. No major differences were detected between the two species in respect to their potency to form callus or to the regeneration capacity. The regeneration capacity of calli decreased gradually and ended after 6 months in culture.
TL;DR: Globular, heart-shaped and torpedo-shaped embryoids have differentiated from explants of ungerminated chestnut cotyledon cultured in vitro on a solid mineral medium, and bipolar structures are interpreted as being globular to cotYledonary stages of embryoid development.
TL;DR: Cytological investigations with light microscopy demonstrated differentiation of embryogenic nodules and early stages of development of somatic embryos in immature corn embryos isolated on the 21st and 30th day after pollination.
TL;DR: Anatomical studies showed that initiation of callus takes place by meristematic activity in epidermal cells of leaves, and cortical cells of roots, and Cytological investigations revealed no change in chromosomal complement.
TL;DR: Zeatin metabolites were isolated from seedcoats and pod tissues of Phaseolus vulgaris and P. lunatus embryos and the major metabolite was the mononucleotide of zeatin and the array of metabolites recovered was not influenced by the extraction method.
Abstract: Zeatin metabolites were isolated from seedcoats and pod tissues of Phaseolus vulgaris and P. lunatus. The differences observed previously between P. vulgaris and P. lunatus embryos, i.e. the formation of O-ribosyl derivatives in the former and O-glucosyl derivatives in the latter, could also be detected in seedcoats, although the levels of these metabolites were much lower and there was a concomitant increase of breakdown products (adenine, adenosine and AMP). Inner pod wall tissues of both genotypes metabolized zeatin at a slow rate and the major metabolite was the mononucleotide of zeatin. The array of metabolites recovered was not influenced by the extraction method (cold ethanol or modified Bieleski solution).
TL;DR: The cytokinin promotion of NADH oxidation by peroxidase may result from an interaction of the hormones with copper, with peroxIDase conferring a specificity similar to the cytokinins specificity observed in growth and development.
Abstract: Apparently free-base cytokinins can interact with cupric ions in a specific manner. Oxidation of NADH by a horseradish peroxidase system was strongly promoted by such cytokinins provided cupric ions were present. Oxidation was promoted by 5 micromolar kinetin, zeatin, 6-benzylaminopurine (BA), or 6-(Δ2-isopentenylamino)purine (2iP) but not by adenine, 6-methylaminopurine or 6,6-dimethylaminopurine. The 6-methylaminopurine promoted oxidation at 500 micromolar but adenine and 6,6-dimethylaminopurine did not. Activity of the free-base purines correlated well with their activity in cell-division assays. However, addition of methoxymethyl-, cyclohexyl-, or tetrahydropyranyl- at N-9 of BA or of ribosyl- at N-9 of BA, 2iP, kinetin, or zeatin eliminated activity in the peroxidase system. In a nonenzymic system containing cupric ions, all of the bases, including adenine, inhibited the Cu2+ -stimulated oxidation of ascorbic acid. As in the peroxidase system, the N-9 derivatives were inactive. The cytokinin promotion of NADH oxidation by peroxidase may result from an interaction of the hormones with copper, with peroxidase conferring a specificity similar to the cytokinin specificity observed in growth and development.
TL;DR: The morphogenic response of 6 mm explants was potentiated by low concentrations of zeatin and a five fold increase was obtained with a concentration of 5.0 mg/l, and IAA present at high concentration inhibited formation of adventitious buds in 6 mmExplants.
Journal Article•
TL;DR: The results of chromatographic analyses suggest, that substances stimulating the soybean callus are likely to be: riboside 6 (gamma, gamma-dimethylallylamino) purine and ribosides zeatin, which are produced by Rhizopogon luteolus.
Abstract: Studies on the effect of post culture liquids of actinomycetes on cytokinin-like substances production by mycorrhizal fungi have revealed that actinomycete metabolites inhibited or stimulated the synthesis of these compounds. The results of chromatographic analyses suggest, that substances stimulating the soybean callus are likely to be: riboside 6 (gamma, gamma-dimethylallylamino) purine and riboside zeatin. Using gas chromatography it was confirmed that both substances are produced by Rhizopogon luteolus. Paxillus involutus synthesizes probably besides the two substances also zeatin, as appears from the data obtained by column chromatography.
TL;DR: The higher cytokinin content of the curly birch sap may explain the poorer apical dominance of curly birches, and possibly even the curly-grained wood formation itself, which can be interpreted as being due to a gall-type cell division activity.
TL;DR: Endogenous levels of cytokinin nucleotides in an anise cell culture were determined during proembryonal, as well as embryonal development, indicating a major role to cytokinins in cell division, but not in embryo differentiation.
Abstract: Endogenous levels of cytokinin nucleotides in an anise cell culture were determined during proembryonal, as well as embryonal development. In both cultures the maximum level of isopentenyladenine nucleotides was found during the first four days of incubation which correlated with the beginning of logarithmic growth (embryonal: 8 ng g−1 tresh weight; proembryonal: 17.4 ng g−1 fresh weight). The concentration of zeatin nucleotides remained constant at a very low level. The present data and those of Ernst et al. (1984) and Ernst and Oesterhelt (1984) are concerned in ascribing a major role to cytokinins in cell division, but not in embryo differentiation.
TL;DR: Purified extracts of developing fruits of “Shamouti’ orange, derived from leafy and leafless inflorescences, showed two paper chromatographic zones of cytokinin activity by the Amaranthus bioassay, which appeared to be relatively higher in fruit from the leafy than in Fruit from the Leafless inflorescence type.
TL;DR: Endogenous cytokinin activity was determined in the flowers of Cosmos sulphureus Cav.
Abstract: Endogenous cytokinin activity was determined in the flowers of Cosmos sulphureus Cav. from bud emergence to full bloom using the soybean callus bioassay. Cytokinin activity was low early in flower development but increased prior to full bloom. In Sephadex LH-20 column chromatography of flower extracts, the cytokinins present co-eluted with zeatin, zeatin riboside and glucoside cytokinin. While the former two predominated prior to full bloom, cytokinin glucoside activity appeared to be at a maximum at full bloom. The possible relevance of these findings is discussed in relation to flower development.
TL;DR: Full grown plants have been raised successfully in vitro by culturing meristems excised from rhizome of Hedychium roxburghii Blume on Murashige and Skoog's medium supplemented with NAA and kinetin.
Abstract: Full grown plants have been raised successfully in vitro by culturing meristems excised from rhizome of Hedychium roxburghii Blume on Murashige and Skoog's medium supplemented with NAA and kinetin. Zeatin associated with IAA stimulated the development of buds on the basal region of the stem. A low concentration of NAA (0.2 mg.1-1) enhanced the root formation on young excised buds.
TL;DR: A range of endogenous cytokinins have been identified in Datura crown-gall tissue by GC-MS and metabolism studies usingcis- andtrans-isomers of zeatin riboside indicate that interconversion of the two isomers does not occur in this tissue.
Abstract: A range of endogenous cytokinins have been identified inDatura crown-gall tissue by GC-MS. Incorporation of [3H]adenine into zeatin riboside, zeatin and its nucleotide(s) is also shown. Metabolism studies usingcis- andtrans-isomers of zeatin riboside indicate that interconversion of the two isomers does not occur in this tissue. Data on the identity of major endogenous cytokinins in a genetic tumour line of tobacco is also provided.
TL;DR: Protocols were established for achieving plant regeneration from stem internode, callus, and cell suspension cultures of Solanum lycopersicoides Dun and zeatin was found most effective relative to number, rapidity of response and overall quality of shoots.
Abstract: Protocols were established for achieving plant regeneration from stem internode, callus, and cell suspension cultures of Solanum lycopersicoides Dun. Two accessions of S. lycopersicoides exhibited different responses as to callus formation on various media, requirement of gibberellic acid for shoot regeneration, and ability to grow in suspension culture. The optimum medium for initiation and maintenance of cell suspension cultures was Murashige and Skoog [9] medium with 15 mg l− NAA. For shoot regeneration, of three cytokinins tested, zeatin was found most effective relative to number, rapidity of response and overall quality of shoots. Shoot regeneration from stem explants, callus and suspension cultures was optimum on MS + 3.0 mg l−1 zeatin + 0.1 mg l−1 gibberellic acid.
TL;DR: An interaction between natural cytokinins and trigonelline in control of the cell cycle in peas and soybeans is reported, the first report of an interaction of two naturally occurring hormones that affect cell arrest in either G1 or G2 in tissues of either plants or animals.