Metabolism and biological significance of benzyladenine-7-glucoside

Gawer, Meryem; Laloue, Michel; Terrine, Claude; Guern, J.

doi:10.1016/0304-4211(77)90192-4

Cited by 33 publications

(21 citation statements)

References 11 publications

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“…Although cytokinin metabolism has been studied in numerous tissues which respond to cytokinin, there is only one previous investigation which was designed so that deductions could be made regarding the significance of metabolites. From several studies of cytokinin metabolism in tobacco cell cultures, Laloue and coworkers obtained evidence that 7-glucosides are not detoxification products of supplied cytokinin and that cytokinin bases may be the active form (Gawer et al 1977;Laloue and Pethe 1982).…”

Section: Discussionmentioning

confidence: 95%

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Letham

Gollnow

1985

J Plant Growth Regul

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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. When 3H-labeled zeatin was supplied to developed cotyledons, at high concentrations (100 I~M), 7-glucosylzeatin was the principal metabolite, but an appreciable proportion of the extracted 3H 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

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Section: Discussionmentioning

confidence: 95%

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Letham

Gollnow

1985

J Plant Growth Regul

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“…regulator taken up because of the conversion of the biologically active molecules into derivatives of unknown activity or no activity at all (1, 6,8,9,12,23,24). The cytokinin conjugates formed are glucosides, ribosides, and ribotides.…”

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confidence: 99%

Cytokinins and Flower Bud Formation in Vitro in Tobacco

Krieken¹,

Croes²,

Smulders³

et al. 1990

Plant Physiol.

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Explants from flower stalks of Nicotiana tabacum L. were cultured on different cytokinins to induce flower bud formation. All cytokinins tested except zeatin and zeatin-riboside induced the same maximal number of flower buds. Benzyladenine, benzyladenosine, and dihydrozeatin were the most active compounds whereas isopentenyladenosine and isopentenyladenine acted at a 20-fold higher concentration. These data suggest that the active cytokinins bind to the same receptor with different affinities. The presence of benzyladenine in the medium was necessary only during the first 2 days of culture (initiation period). The equilibrium between benzyladenine and its conjugates (the riboside, glucoside, and nucleotides) after a 4-day pulse was independent of the benzyladenine concentration whether it was inductive or noninductive for bud formation. The level of all derivatives was proportional to the benzyladenine concentration in the medium. Isopentenyladenine was used as a competitive inhibitor of benzyladenine conjugation. Isopentenyladenine concentrations that were too low for bud formation led to a synergistic increase in bud number when applied together with benzyladenine. Isopentenyladenine decreased benzyladenine uptake and conjugation. In spite of the lower uptake, the concentration of free benzyladenine inside the explants was higher in the presence of isopentenyladenine than in its absence whereas the concentration of the 7-glucoside of benzyladenine was lower. It was concluded that the free cytokinin base is the main active compound.The regeneration of organs in small explants from plant tissues offers the possibility to study differentiation on tissues spatially isolated from the whole plant. In this way the qualitative and quantitative response to auxins and cytokinins involved in the regulation of developmental processes can be studied. In tobacco, both the effects of the concentrations and of the ratios of these plant growth regulators on the induction and frequency of roots and/or shoots ( 16) or flower buds (20) have been described. In attempting to understand the mechanism of action of these plant growth regulators, it is important to relate the number of regenerated organs to the actual endogenous auxin and cytokinin concentrations. These concentrations cannot be determined from the amount of growth ' Present address: Department of Botany, University of Guelph, Guelph, Ontario N1G 2W1, Canada. 565regulator taken up because of the conversion of the biologically active molecules into derivatives of unknown activity or no activity at all (1,6,8,9,12,23,24). The cytokinin conjugates formed are glucosides, ribosides, and ribotides. Generally, the glucosides are considered stable and inactive. In contrast, the free base and perhaps also the ribosides and ribotides are active (1 1, 13).Little research has been performed on cytokinin metabolism in relation to developmental processes in plants. Van der Krieken et al. (22) (18), is very well suited to study cytokinin metabolism in relation to flower b...

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“…Horgan (7) showed that 7-glucosylzeatin was not formed in cytokinin-requiring soybean callus, 6(4-0-,8-D-glucosyl-3-methyltrans-2-butenylamino) purine being the major metabolite present 24 hr after the zeatin had been sup-I This research was partly supported by Centre National de la Recherche Scientifique, Equipe de recherche associee N 486. plied. We also obtained evidence that 7-glucosylbenzyladenine biosynthesized in tobacco cells is not active per se but rather represents a storage form of the cytokinin (6).…”

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confidence: 69%

Cytokinins: Metabolism and Biological Activity of N⁶-(Δ²-Isopentenyl)adenosine and N⁶-(Δ²-Isopentenyl)adenine in Tobacco Cells and Callus

Laloue¹,

Terrine²,

Guern³

1977

Plant Physiol.

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The cytokinin, N6-(A2-isopentenyl)adenine, is found to be at least 3.3 times as active as N6-(A2-isopentenyl)adenosine in promoting the growth of cytokinin-requiring tobacco (Nicotiana tabacum) callus. Absorption rates of N6-(A2-isopentenyl)adenine and N6-(A2-isopentenyl)adenosine by tobacco cells in liquid suspension do not differ significantly. In these cells, N6-(A2-isopentenyl)adenosine-5'-monophosphate, di-, and triphosphate are synthesized in both cases, but 7-glucosylation occurs significantly only with N6-(A2-isopentenyl)adenine, protecting thereby its N6-isopentenyl side chain from cleavage. Degradation by N6-side chain removal appears to be intense, leading to the formation of adenine, adenosine, and adenylic nucleotides. Thus, it is suggested that N6-(A2-isopentenyl)adenine-7-glucoside is a protected or storage form of the cytokinin which could account for the higher biological activity of N6-(A2-isopentenyl)adenine than of N6-(A2-_sopentenyl)adenosine.In the last years, metabolism of exogenously supplied cytokinins has been studied in various plant tissues and plant cells. Since the reports of the formation of the unusual 7-glucosylbenzyladenine in various plant tissues (1) and 7-glucosylzeatin in radish cotyledons (19) as major and highly active (4, 18) cytokinin metabolites of the supplied cytokinin, attention has been focussed on cytokinin glucosides (7,10,13,20,26).However, cytokinin glucosides are not the only cytokinin metabolites synthesized from exogenously supplied cytokinin that keep the intact cytokinin base moiety. In most of the studies cited above and in other studies (2, 24), cytokinin riboside and cytokinin riboside-5'-monophosphate were also found to be synthesized. In a previous communication (12), we established the formation of cytokinin riboside-5'-di and triphosphates in tobacco and Acer cells.So far, the only correlation that could be established between cytokinin metabolism and cytokinin activity were based on the cytokinin-requiring growth of plant tissues grown as callus and cytokinin metabolites that were present in this callus. Fox et al.(5) found that 7-glucosylbenzyladenine was the only cytokinin molecule that persisted during the active growth of cytokininrequiring soybean callus and tobacco KX4 callus, suggesting that 7-glucosylbenzyladenine could be the "physiologically active form of the cytokinin" (4). Horgan (7) showed that 7-glucosylzeatin was not formed in cytokinin-requiring soybean callus, 6(4-0-,8-D-glucosyl-3-methyltrans-2-butenylamino) purine being the major metabolite present 24 hr after the zeatin had been sup-

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Metabolism and biological significance of benzyladenine-7-glucoside

Cited by 33 publications

References 11 publications

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Cytokinins and Flower Bud Formation in Vitro in Tobacco

Cytokinins: Metabolism and Biological Activity of N⁶-(Δ²-Isopentenyl)adenosine and N⁶-(Δ²-Isopentenyl)adenine in Tobacco Cells and Callus

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Metabolism and biological significance of benzyladenine-7-glucoside

Cited by 33 publications

References 11 publications

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Regulators of cell division in plant tissues. XXX. Cytokinin metabolism in relation to radish cotyledon expansion and senescence

Cytokinins and Flower Bud Formation in Vitro in Tobacco

Cytokinins: Metabolism and Biological Activity of N6-(Δ2-Isopentenyl)adenosine and N6-(Δ2-Isopentenyl)adenine in Tobacco Cells and Callus

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Cytokinins: Metabolism and Biological Activity of N⁶-(Δ²-Isopentenyl)adenosine and N⁶-(Δ²-Isopentenyl)adenine in Tobacco Cells and Callus