Showing papers on "Zeatin published in 1986"
TL;DR: Cytokinin-like substances in both healthy and infected roots of Brassica campestris L. ssp.
Abstract: Cytokinin-like substances in both healthy and infected (Plasmodiophora brassicae) Wor. strain S) roots of Brassica campestris L. ssp. pekinensis cv. Granat have been tentatively identified and quantified by HPLC. The isomers of the cytokinins could be seperated on a reversed phase column using a gradient elution with increasing amounts of methanol. Secondary plasmodia were isolated mechanically from Plasmodiophora brassicae infected roots. The time course of adenine uptake and its conversion to cytokinins were investigated. Evidence is presented for the incorporation of [U-14C]-adenine into trans-zeatin by secondary plasmodia.
100 citations
TL;DR: Hardening in vitro by partial desiccation with CaSO 4 under aseptic conditions improved the cucumber plantlet's leaf growth and their survival after transplanting to soil.
76 citations
TL;DR: Examination of cytokinin production by plasmid deletion mutants of PB213-2 and EW1006 indicated that cytkinin biosynthesis was specified, at least in part, by plasmsid-borne genes.
Abstract: Cytokinin production by strains of the phytopathogenic bacterium Pseudomonas syringae pv savastanoi was measured by immunoaffinity chromatography of the culture medium on immobilized anti-cytokinin antibodies, followed by high performance liquid chromatography, radioimmunoassay and mass spectrometry. P. savastanoi strain PB213-2 secretes zeatin (80 nanograms per milliliter) and ribosylzeatin (80 nanograms per milliliter). Even higher levels of zeatin (400 nanograms per milliliter) are produced by the olive-specific strain EW1006, which also produces 180 nanograms per milliliter of the recently identified cytokinin, ribosyl-1″ -methylzeatin. The amounts secreted were approximately 1000 times greater than those secreted by Agrobacterium tumefaciens (DA Regier, RO Morris 1982 Biochem Biophys Res Commun 104: 1560-1566). Examination of cytokinin production by plasmid deletion mutants of PB213-2 and EW1006 indicated that cytokinin biosynthesis was specified, at least in part, by plasmid-borne genes. A fragment of the 105 kilobase pair plasmid from EW1006 was cloned into Escherichia coli where its expression resulted in dimethylallyl transferase activity and the secretion of zeatin.
72 citations
TL;DR: The first step of root formation corresponded to a high IAA/Z + ZR ratio in the root-forming tissue, whereas the second step was characterized by a low ratio with low levels of hormones, and C hypocotyls recovered the initial high levels when roots regenerated (day 5).
Abstract: Indole acetic acid (IAA). abscisic acid (ABA), and zeatin plus zeatin riboside (Z + ZR) were determined daily in cuttings of Lycopersicon esculentum Mill. cv. Craigella (C) and the Craigella Lateral Suppressor (CLS) mutant during the first 5 days of the root-forming process. A solid-phase enzyme immunoassay using specific anti-hormone antibodies was used following a one-step HPLC purification procedure. The hormone measurements were made in cuttings divided into 4 parts. The main variations occurred in the terminal bud and in the basal part of the hypocotyl of the two tomato varieties, i.e. significant IAA and ABA increases during the first 2 days followed by a more or less fast return to the initial values at day 4 or 5. This is probably due to the ablation of the root system. Z + ZR levels dramatically decreased in the basal part of the Craigella hypocotyl 1 day after cutting. Contrary to CLS, C hypocotyls recovered the initial high levels when roots regenerated (day 5). This is probably linked to the greater ability of roots to produce cytokinins in C plants than in CLS ones. The first step of root formation (reactivation of the pericyclic cells and formation of root primordia) corresponded to a high IAA/Z + ZR ratio in the root-forming tissue, whereas the second step (elongation of young roots) was characterized by a low ratio with low levels of hormones.
71 citations
TL;DR: The results indirectly support the hypothesis that endogenous cytokinins prevent root formation in stems of intact plants and may be of importance for the regulation of rooting in cuttings.
Abstract: Benzylaminopurine (BAP) or zeatin continuously supplied through the rooting solution to cuttings of pea (Pisum sativum L. cv. Weibull's Marma), inhibited root formation down to a concentration of 3.10−9M. The inhibitory effect of BAP in the concentration range 10−8–10−7M was readily reversible if the cuttings were transferred to solutions without cytokinin after treatment for 1–4 days. A slight increase in the number of roots formed was obtained after treatment with low cytokinin concentrations for 1–2 days. Evidence from microscopic studies of primordia formation indicates that BAP inhibits differentiation of primordia at an early stage in their development. Growth of already formed primordia, or root elongation, was considerably less sensitive to the inhibitory effect of BAP. The results indirectly support the hypothesis that endogenous cytokinins prevent root formation in stems of intact plants and may be of importance for the regulation of rooting in cuttings.
57 citations
TL;DR: Both high concentrations of minerals and the addition of 10 μM riboflavin to the culture medium reduced callus growth and improved shoot growth and quality of Carica papaya.
Abstract: SummaryStudies were made of nutritional and hormonal factors affecting shoot and callus growth from apical and lateral bud explants of Carica papaya. Both high concentrations of minerals and the addition of 10 μM riboflavin to the culture medium reduced callus growth and improved shoot growth and quality. The promotion of shoot growth by cytokinin was greatly reduced when riboflavin was absent. Increasing auxin concentration reduced shoot growth; however this effect was removed when riboflavin was added. Six auxins (IAA, IBA, NAA, NOA, pCPA and 2,4-D) and five cytokinins (kinetin, 2iP, zeatin, PBA and BAP) were applied individually over a range of concentrations and the resultant growth was observed and recorded. Best shoot growth occurred when 1 μ mol l−1 of both NAA and BAP were added to a modified de Fossard et al. (1974) basal medium. High concentrations of auxin in the medium caused deformed shoot growth, whereas high concentrations of BAP and PBA caused excessive callus production.
51 citations
TL;DR: It was concluded that the stimulation of ethylene production in cotton leaves following cytokinin treatment was the result of an increase in both the formation and oxidation of ACC.
Abstract: The influence of cytokinins on ethylene production was examined using cotton leaf tissues. Treatment of intact cotton (Gossypium hirsutum L. cv LG 102) seedlings with both natural and synthetic cytokinins resulted in an increase in ethylene production by excised leaves. The effectiveness of the cytokinins tested was as follows: thidiazuron ≫ BA ≫ isopentyladenine ≥ zeatin ≫ kinetin. Using 100 micromolar thidiazuron (TDZ), an initial increase in ethylene production was observed 7 to 8 hours post-treatment, reached a maximum by 24 hours and then declined. Inhibitors of 1-aminocyclopropane-1-carboxylic acid (ACC) synthesis and its oxidation to ethylene reduced ethylene production 24 hours post-treatment; however, by 48 hours only inhibitors of ACC oxidation were effective. The increase in ethylene production was accompanied by a massive accumulation of ACC and its acid-labile conjugate. TDZ treatment resulted in a significant increase in the capacity of tissues to oxidize ACC to ethylene. Endogenous levels of methionine remained constant following TDZ treatment. It was concluded that the stimulation of ethylene production in cotton leaves following cytokinin treatment was the result of an increase in both the formation and oxidation of ACC.
48 citations
TL;DR: Taxonomic examination of the cytokinin-producing bacteria showed that the production of the hormone was not specific to any genus, and a possible role of cytokinins produced by sediment bacteria on the development of red tide is discussed.
Abstract: Plant hormones, which are considered to be cytokinins, were detected in the culture media of marine bacteria using the Amaranthus bioassay method. The proportion of cytokinin-producing bacteria to total microbes tested was higher in sediments (45–55%) than in seawater (5–15%). The amount of cytokinin-like substances in the culture media was estimated as 0.05–0.30 μg of zeatin equivalents/l. Thin layer chromatography analysis using the soybean callus bioassay method suggested that the active substance produced by one of these bacteria was isopentenyladenine or its riboside. Taxonomic examination of the cytokinin-producing bacteria showed that the production of the hormone was not specific to any genus. A possible role of cytokinins produced by sediment bacteria on the development of red tide is discussed.
44 citations
Journal Article•
35 citations
TL;DR: Kinetin inhibited appressorium formation apart from the host on nitrocellulose membranes, suggesting that the inhibitory effects of kinetin on fungus development were direct rather than through the host.
30 citations
TL;DR: Micropropagation of carob is possible from seedlings and mature trees using Murashige and Skoog medium with 5 μM zeatin for shoot multiplication and 10 μM indole-butyric acid for root induction.
TL;DR: It seems that each of the cytokinins studied is active per se and that there is no common, active metabolite between them.
TL;DR: Solanum nigrum protoplasts were co-cultivated with Agrobacterium rhizogenes harboring agropine-type Ri plasmid with results that showed hairy roots appeared on MS medium without plant growth regulator.
Abstract: Solanum nigrum protoplasts were co-cultivated with Agrobacterium rhizogenes harboring agropine-type Ri plasmid (pRi15834). A large number of transformed calli were obtained on Murashige and Shoog's (MS) medium lacking plant growth regulators. Frequency of transformation was about 3.5×10−3. In most of the calli, hairy roots appeared on MS medium without plant growth regulator. When the hairy roots were cut into segments and subcultured on MS medium lacking plant growth regulators, calli were readily formed. Plantlets were regenerated by transferring those calli to MS medium supplemented with 1 mg/l zeatin and 0.2 mg/l naphthaleneacetic acid. Frequency of plant regeneration was about 70%.
TL;DR: Both kinetin (KN) and zeatin (Z) proved ineffective in inducing shoot buds or shoots and the addition of 2,4-dichlorophenoxyacetic acid to the growth medium suppressed root formation.
TL;DR: A survey of 30 species of woody plants in 20 families of dicotyledonous angiosperms indicated that the ability to accumulate io6Ade in 24-hr feeds with 30 μM i 6Ade was restricted to certain systematic groups—e.g., order Ericales, families Oleaceae and Rubiaceae.
Abstract: Tissue cultures of Actinidia kolomikta can be maintained as callus through repeated passages on a nutrient medium devoid of cytokinin but containing inorganic nutrients, sucrose, and other basal organics plus auxin. Under these conditions, actively growing callus contained 2 and 0.5 nmol of the cytokinins zeatin [io6Ade; 6-(4-hydroxy-3-methylbut-2-enylamino)purine] and N6-(Δ2-isopentenyl)adenine (i6Ade), respectively, per gram (fresh weight). When tissues were transferred from cytokininless medium to 30 μM i6Ade, endogenous io6Ade increased linearly to 160 nmol/g (fresh weight) during 8 hr, and i6Ade increased to 5 nmol/g (fresh weight) in 2 hr and then declined. The apparent Km for i6Ade in A. kolomikta and Actinidia chinensis × Actinidia arguta callus and in tissue slices of A. arguta stems was 12 μM. In addition, the reaction(s) converting i6Ade to io6Ade was O2-requiring and specific for i6Ade versus N6-(Δ2-isopentenyl)adenosine (i6A). When A. kolomikta callus was fed 30 μM i6A, io6Ade increased and reached a concentration corresponding to 6 nmol/g (fresh weight) in 8 hr. Ribosylzeatin (io6A) did not increase. Under N2 during i6A feeds, i6A accumulated rather than being metabolized to i6Ade, suggesting that i6A normally may be metabolized via i6AMP and i6Ade to io6Ade. A survey of 30 species of woody plants in 20 families of dicotyledonous angiosperms indicated that the ability to accumulate io6Ade (≥10 nmol/g) in 24-hr feeds with 30 μM i6Ade was restricted to certain systematic groups—e.g., order Ericales, families Oleaceae and Rubiaceae. This suggests that plants may differ in their pathways for io6Ade biosynthesis and that cytokinin biochemistry has potential as a taxonomic character above the species and genus levels.
TL;DR: The isolation and structural elucidation of 1′-methyl-zeatin, a novel cytokinin, is reported and its role in cell reprograming is described.
TL;DR: Root tips, entire roots, and entire seedlings of Zea mays were cultured in a modified B5 medium containing kinetin, zeatin, or 6-benzylaminopurine at either 0.46 or 4.65 μM and fluorescent microscopic analyses showed expansion and partial isolation of cortical cells in cytokinin-treated roots.
Abstract: Root tips, entire roots, and entire seedlings of Zea mays were cultured in a modified B5 medium containing kinetin, zeatin, or 6-benzylaminopurine at either 0.46 or 4.65 μM. After 6 days, the diameter of the root tips in all three cytokinin-containing media was ca. fourfold that of the controls. Fluorescence microscopic analyses of the cytokinin-treated roots showed expansion and partial isolation of cortical cells. Files of cells were separated by intercellular spaces parallel to the root axis. Electron microscopic observations indicated that the cell isolation resulted from dissolution of the middle lamellae. Ethylene was not involved in cell expansion and cell isolation. Cytokinin-induced separation of the cortical cells probably resulted from the intensification of localized cell wall loosening in the growing root.
TL;DR: Combinations involving indole-3-acetic acid with any of the cytokinins were more effective in inducing shoot bud formation compared to those containing indole -3-butyric acid or α-napthalenacetic Acid as an auxin.
Abstract: The effects of serial combinations of either indole-3-acetic acid, indole-3-butyric acid or α-naphthaleneacetic acid (0.5–10.0 mg/l) with either kinetin, 6-benzyl-amino-purine, zeatin or 6-methylaminopurine (0.5–5.0 mg/l) have been investigated to assess the morphogenetic potential of foliar explants of Duboisia myoporoides. Shoot buds developed either directly or via a callus interphase. Combinations involving indole-3-acetic acid with any of the cytokinins were more effective in inducing shoot bud formation compared to those containing indole-3-butyric acid or α-napthalenacetic acid as an auxin. Among cytokinins, zeatin, kinetin and 6-benzylamino-purine were equally effective for shoot formation. However, optimum response with zeatin could be achieved at low concentrations (0.5–2.0 mg/l), while kinetin and 6-benzylamino-purine exhibited comparable efficacy at higher levels (3.0–5.0 mg/l). 6-Methylaminopurine proved least effective in all concentrations and combinations tested. Rooting of the differentiated shoots was readily achieved with α-naphthaleneacetic acid alone (0.5 mg/l) after changing the physical form of the medium from gel to static liquid. Regenerated plantlets were transferred to pots and grown to maturity in the field with a high rate of survival (80–90%).
01 Jan 1986
TL;DR: The realization that the kinetin effect could be replaced by extracts from many plant tissues triggered the search for endogenous cytokinins, resulting in the isolation of the first natural cytokinin, zeatin from immature Zea mays kernels (Letham 1963; Letham et al. 1964, 1967).
Abstract: Cytokinin is a generic term proposed to define both naturally occurring and synthetic compounds that induce cell division in plant tissue cultures (e.g., tobacco stem pith, soybean cotyledonary callus and carrot secondary phloem etc.) grown on defined medium in the presence of an optimal concentration of auxin. Although the idea that specific chemical substances may control cell division in plants dates back to the nineteenth century (Wiesner 1892), it first received experimental support only in the early 1920’s following the observation that wounding induced cell division in many plant tissues, e.g., potato parenchyma (Haberlandt 1921). Kinetin (Fig. 1) was the first cytokinin to be identified, and its isolation in 1956 from autoclaved herring sperm DNA was a direct consequence of studies on growth requirements of plant tissue cultures (Miller et al. 1956). It does not occur per se in living tissues, and had resulted as an artefact of the autoclaving process in the original work. Synthetic kinetin was found to be a very potent promoter of cell division, and induced cell division activity in the tobacco pith assay at concentrations as low as 1 μg 1 −1. The realization that the kinetin effect could be replaced by extracts from many plant tissues triggered the search for endogenous cytokinins, resulting in the isolation of the first natural cytokinin, zeatin [6-(4-hydroxy-3-methylbut-trans-2-enylamino) purine] from immature Zea mays kernels (Letham 1963; Letham et al. 1964, 1967). The number of cytokinins identified so far from diverse natural sources is nearing 30. In addition to their occurrence as free compounds in higher plants, cytokinins have also been isolated from transfer ribonucleic acid (tRNA) hydrolysates of plants, animals and microorganisms (Letham and Wettenhall 1977; Letham and Palni 1983).
TL;DR: In this article, the role of cytokinins in the senescence of G2 peas was determined using gas chromatography-mass spectroscopy following purification by HPLC, and the presence of zeatin was confirmed by its mass spectrum of its permethylated derivative.
Abstract: In G2 peas senescence only takes place in long days. In order to determine the role of cytokinins in this process the endogenous cytokinins from vegetative shoots of G2 peas were characterized using gas chromatography-mass spectroscopy following purification by HPLC. Cytokinins were extracted and purified with and without the addition of 15N labelled internal standards of several cytokinins to estimate cytokin content by isotope dilution in the mass spectra. Samples without internal standards were bioassayed after HPLC. Bioassays showed the presence of zeatin, zeatin riboside and zeatin-0-glucoside. The presence of zeatin was confirmed by its mass spectrum of its permethylated derivative. Tentative identification of zeatin riboside, zeatin-0-glucoside, dihydrozeatin, and dihydrozeatin-0-glucoside was obtained by the coincidence of the major ion for the permethylated natural and 15N labelled internal standards on GC-MS, and the similar coincidence of ions for permethylated zeatin riboside-0-glucoside by direct probe MS. There was no indication of the presence of significant quantities of zeatin-7-glucoside or zeatin-9-glucoside. The amounts in the tissue ranged from 200–1000 ng/kg fresh weight for each cytokinin and about 2–4 μg/kg fresh weight for total cytokinins. There was no apparent difference in the levels in mature but pre-senescent shoots grown in long days and short days indicating that apical senesecence in G2 peas does not appear to be induced by a decline in cytokinin level in the shoots.
TL;DR: Callus cultures of Cinchona ledgeriana were established from seeds obtained from Kenya on Gamborg's B5 medium containing 2% glucose, 1 mg l −1 2,4-D and 0.25 mg l -1 kinetin to determine the effect of 240 combinations of auxins and cytokinins on growth and alkaloid production.
TL;DR: GLC analysis of purified extracts indicates that t zeatin, 2IP, their respective riboside and ri-botide, and tZeatin and t ribosyl-zeatin glucosides are present in chicory root.
01 Jan 1986
TL;DR: Results are in agreement with the hypothesis that deficiency of growth substances like cytokinins plays an important role in the occurrence of flower-bud blasting, and for the major endogenous cytokinin, isopentenyl-adenosine.
Abstract: The effect of dark and light treatment on endogenous cytokinins in internodes and buds ofIris was determined. Plant material was purified by chromatographic methods and cytokinins were assayed by an immunoassay . An indirect competitive enzyme immunoassay for the determination of zeatin- and isopentenyl-adenine cytokinins was developed . This assay, which is not dependent on the titre of the antibodies raised against zeatin riboside and isopentenyl-adenosine appeared to be specific, highly sensitive and more reproducible compared to a direct competitive enzyme immunoassay for cytokinins. Isopentenyl-adenosine was the most abundant cytokinin found, followed by zeatin : the latter counteracts bud blast when injected into dark-treated plants . Smaller amounts of isopentenyl-adenine and zeatin riboside were found . Results are in agreement with the hypothesis that deficiency of growth substances like cytokinins plays an important role in the occurrence of flower-bud blasting . A possible role for the major endogenous cytokinin, isopentenyl-adenosine, which earlier was found not to be effective in counteracting bud blast when injected into buds of dark-treated plants, is discussed .
TL;DR: The results suggest that root and stem tissues may be sites of cytokinin biosynthesis in growing Actinidia plants and that cytokinIn production may not be the critical factor controlling the beginning of shoot growth in the spring.
Abstract: In Actinidia arguta (hardy kiwifruit) plants, the potential to accumulate the cytokinin zeatin (io6Ade) during feeding with a precursor, N6-(Δ2-isopentenyl)adenine (i6Ade), varies depending on the tissue. This can be demonstrated by incubating explants for 24 hr on a basal nutrient medium supplemented with 30 μM i6Ade and then extracting the tissues and analyzing cytokinin contents using HPLC methodology. Under these conditions, the potential for io6Ade accumulation in tissue slices from growing roots was 93 nmol/g at the root tip, >200 nmol/g immediately behind the tip (1.0-mm diameter), ≈100 nmol/g in 2-mm diameter root, and progressively lower in older tissues. A similar gradient of io6Ade accumulation was detected in growing stems, with relatively low activity (40 nmol/g) in the terminal 0.5 cm, ≈170 nmol/g in the 5- to 15-cm interval, and about 25 nmol/g in stem tissues taken 15-100 cm from the tip. Growing leaves accumulated little io6Ade (7-26 nmol/g) during feeding, as did fruits (0-8 nmol/g) at various stages of development and maturation. Seasonally, root activity was detected as early as March 1, whereas stem activity did not appear until March 15. Thus, the activation of i6Ade metabolism in both of these organs preceded sap flow (March 29) and bud break (April 16) by several weeks. The results suggest that root and stem tissues may be sites of cytokinin biosynthesis in growing Actinidia plants and that cytokinin production may not be the critical factor controlling the beginning of shoot growth in the spring.
TL;DR: Feeding of [8- 14 C]adenine to immature caryopses of Zea mays for periods of up to five days did not result in the incorporation of any radioactivity into compounds with similar chromatographic properties to those of the authentic cytokinins.
TL;DR: Isopentenyladenine, a trace component in plant food and a plant hormone, can affect the metabolism of an animal cell line of myoblasts and it dose-dependently enhanced the proliferation and DNA synthesis of the cells.
Abstract: The effects of cytokinins, a class of plant hormones, on cell proliferation and protein synthesis were studied in rat-derived L6 myoblasts cultured in a serum-free medium. Of the three cytokinins tested, isopentenyladenine, zeatin and ribosylzeatin, isopentenyladenine (5 μm) most stimulated the growth and DNA synthesis of the myoblasts, and it dose-dependently (0 ~ 10μm) enhanced the proliferation and DNA synthesis of the cells. Isopentenyladenine (5 and 10 μm) increased protein synthesis to twice that of control (0μm). These results suggest that isopentenyladenine, a trace component in plant food and a plant hormone, can affect the metabolism of an animal cell line of myoblasts.
TL;DR: The results obtained provide strong evidence for a role of cytokinins in flowering of Lema paucicostata LP 6 in nature and are indicative of the possibility that their effect on flowering may be exerted through a stimulative effect on uptake of iron.
TL;DR: Two anticytokinins induced lateral bud growth of Lycopersicon esculentum Mill.
Abstract: The action of two anticytokinins, 3-methyl-7-n-pentyl-aminopyrazolo[4,3-d] pyrimidine and 4-cyclopentylamino-2-methylthiopyrrolo [2,3-d] pyrimidine on the zeatin and 6-benzylaminopurine induced lateral bud growth ofLycopersicon esculentum Mill. cv. Fireball seedlings was studied. Bud growth stimulation by 0.1 mM zeatin was not overcome by application of anticytokinin at concentrations of 0.01 to 1.0 μ 24-h after zeatin application. However, application of 0.1 μM of anticytokinin 24-h before 0.1 mM zeatin caused a significant enhancement of bud growth. A simultaneous application of 1 mM anticytokinin and 6-benzylaminopurine or concurrent with young leaves excision significantly reduced bud growth.
TL;DR: Petiole segments of Senecio × hybridus were grown in vitro on media containing different cytokinins, auxins and macronutrients, and shoot formation was most prolific on explants grown base downwards, but roots and callus formed more abundantly when the base was oriented upwards.
Abstract: SummaryPetiole segments of Senecio × hybridus were grown in vitro on media containing different cytokinins, auxins and macronutrients. Explants were oriented, some with their morphological base upwards, some downwards and some sideways. IAA promoted shoot formation better than NAA, whereas roots and callus formed more prolifically on media with NAA. BAP was the most active cytokinin in stimulating shoot formation, but more explants formed roots and callus when grown in the presence of zeatin or 2iP, compared with BAP or kinetin. More explants formed organs on media with a high macronutrient concentration than on media with a low concentration. Shoot formation was most prolific on explants grown base downwards, but roots and callus formed more abundantly when the base was oriented upwards. Polarity was influenced by the concentration of growth regulators. Explants grown base upwards had a higher N concentration in the upper part than in the lower part, whereas there was no N gradient in explants grown base...