Cytokinins: Structure/activity relationships

Skoog, Folke; Hamzi, Hamzi Q.; Szweykowska, A.; Leonard, Nelson J.; Carraway, Kermit L.; Fujii, Tozo; Helgeson, John P.; Loeppky, Richard N.

doi:10.1016/s0031-9422(00)86080-x

Cited by 220 publications

(97 citation statements)

References 47 publications

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“…As the compounds tested, which, though chemically closely related to cytokinins, are not active as cytokinins in the callus assay (11) did not restore root-dependent coleoptile growth, this is probably a specific cytokinin effect. The fact that cytokinin is as effective when applied in aqueous solution to the base of seedlings as when applied to the coleoptile tips probably means that the cytokinins are transported to and act in the tips.…”

Section: Discussionmentioning

confidence: 92%

“…However, the capacity of the coleoptile to respond to unilaterally applied auxin (the curvature response) is increased in deseeded plants as compared with intact controls, mainly owing to an increase in the time of active bending. Van Overbeek (11) found that removal of the roots of the Avena seedling brought about a similar decrease in auxin production and an increase in the curvature response of the coleoptile to unilaterally applied auxin. Subsequently Went (13,14) showed that, in tomatoes, shoot growth is dependent upon hormone-like substances supplied by the root.…”

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confidence: 96%

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Effects of Cytokinins on Growth and Auxin in Coleoptiles of Derooted Avena Seedlings

Jordan

Skoog

1971

Plant Physiol.

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It is known that removal of the endosperm (deseeding) reduces subsequent auxin production in the oat coleoptile tip and the "regeneration of the physiological tip" (auxin production) in the decapitated coleoptile as determined by the For experiments on the effect of cytokinins on auxin secretion from coleoptile tips, the ethanol-carbowax solutions were applied to the tips either after 56 to 60 hr of growth or just 5 min before excision of the tips. For each treatment 36 2-mm tips were excised with a scalpel after 72 to 74 hr of growth and arranged basal end down on 0.1 5-ml agar platelets. Every hour for 5 hr each set of tips was transferred to a fresh platelet. Each platelet was then divided into 12 blocks for auxin assays by the A vena curvature test.The assay was performed in the standard way (15) with uniform plants selected from the same batch of seedlings from which the experimental plants had been selected. During the assay the relative humidity in the Avena room was maintained near 88%. For quantitation of the response each assay included a standard series of IAA concentrations. RESULTSAs illustrated by a typical experiment (Fig. 1), increase in length of the measured apical portion of the coleoptiles was about 50% less in derooted plants in the 20 hr following derooting than in intact controls. In coleoptiles of derooted plants supplied with 2iP immediately upon derooting the increase was about the same as in intact controls. The increase in intact plants treated with 2iP was only slightly greater than in intact controls. Thus treatment with cytokinin overcomes the effect of * Abbreviations: 2iP: 6-(3-methyl-2-butenylamino)purine; BAP: 6-benzylaminopurine. 97www.plantphysiol.org on May 9, 2018 -Published by Downloaded from

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Section: Discussionmentioning

confidence: 92%

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confidence: 96%

Effects of Cytokinins on Growth and Auxin in Coleoptiles of Derooted Avena Seedlings

Jordan

Skoog

1971

Plant Physiol.

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“…At the lower concentration, large masses of loose, friable tissue are obtained while at the higher concentration smaller, hemispheric discs tend to form (7). Both types of tissues grow logarithmically.…”

Section: Methodsmentioning

confidence: 97%

Modification of Logarithmic Growth Rates of Tobacco Callus Tissue by Gibberellic Acid

Helgeson

Upper

1970

Plant Physiol.

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Logarithmic growth rates (either fresh or dry weight basis) of tobacco callus tissues grown on 10-to 10-1 AM cytokinin are increased if gibberellic acid (10-4-2 AM) is incorporated into the medium. At higher (1-10 jM) cytokinin concentrations gibberellic acid has little effect on growth rate but extends the duration of logarithmic growth. The gibberellic acid effect is noticeable only after one weight doubling, is dependent on concentration, and occurs when either glucose or sucrose is used as carbon source. The gibberellic acid response includes a decrease in percentage of dry weight relative to control tissues. The maximum dry weight yield, although achieved sooner than controls, does not differ appreciably from yields of tissue not treated with gibberellic acid.

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“…The antagonist that blocks the action of the endogenous cytokinins in these systems would thus make the tissue cytokinin-dependent. The antagonist would be of greatest utility, of course, if it acted in a reversible manner on the same path- (12). In order to detect anticytokinin activity, the growth of tobacco callus was observed on a standard medium to which either 6-(3-methyl-2-butenylamino)purine or 6-benzylaminopurine had been added (over a range of concentrations) and to which the other compounds (3-6) were also added in different concentrations.…”

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confidence: 99%

“…The antagonist would be of greatest utility, of course, if it acted in a reversible manner on the same path- (11). The cytokinin activities of these compounds were determined in the tobacco bioassay (12). In order to detect anticytokinin activity, the growth of tobacco callus was observed on a standard medium to which either 6-(3-methyl-2-butenylamino)purine or 6-benzylaminopurine had been added (over a range of concentrations) and to which the other compounds (3)(4)(5)(6) were also added in different concentrations.…”

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Cytokinins: Development of a Potent Antagonist

Hecht

Bock

Schmitz

et al. 1971

Proc. Natl. Acad. Sci. U.S.A.

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A systematic search has resulted in the synthesis of a class of cytokinin antimetabolites. The development and biological properties of the anticytokinins are discussed in terms of one member of the class, 3-methyl -7 -(3 -methylbutylamino)pyrazolo [4,3 -dl-pyrimidine. way through which the cytokinin itself exerts its effect. We wish to report the discovery of a series of such compounds, the activity of which is exemplified here by one member of that series, 3-methyl-7-(3-methylbutylamino)pyrazolo [4,3-dipyrimidine (6).The distribution of cytokinins (factors promoting cell division and growth) in natural systems is widespread (1, 2) and includes compounds at the purine, ribonucleoside, ribonucleotide, and tRNA levels (3, 4). Plants presumably require cytokinins for growth, because growth of excised plant tissues is often dependent on an exogenous cytokinin supply. One cytokinin, 6-(3-methyl-2-butenylamino)purine (1) has been shown to be the active factor in the plant pathogen Corynelbacterium fascian8 (5). In addition, phytohemagglutininstimulated human lymphocyte cells are both stimulated and inhibited by 6-(3-methyl-2-butenylamino)-9-1-D-ribofuranosylpurine (2) with respect to DNA synthesis, transformation, -and mitosis (6). The-effect depended upon the stage of the cell cycle and the concentration of 2 employed. Compound 2 has antitumor activity in experimental animals (7, 8) and in preliminary clinical trials (9). In spite of this broad range of physiological activity and the occurrence of several different cytokinins in nature (1), including four as components of tRNA (10), as well as hundreds of synthetic cytokinins (1, 2), only one example of cytokinin antagonism has been reported in a compound that bears an obvious structural relationship to the known cytokinins (5). Although the structural relationship between this compound (6-methylaminopurine) and the -cytokinins suggests its potential utility in studies of the mechanism of cytokinin action, it would probably not be suitable, since it has a very slight activity as an antagonist. To date, no systematic search for compounds that would oppose the action of the cytokinins has been reported.The synthesis of a potent cytokinin antagonist is of considerable interest, since it could extend the study of cytokinins to biological systems that do not require any exogenously added cytokinins, presumably because they produce their own. The antagonist that blocks the action of the endogenous cytokinins in these systems would thus make the tissue cytokinin-dependent. The antagonist would be of greatest utility, of course, if it acted in a reversible manner on the same path- (12). In order to detect anticytokinin activity, the growth of tobacco callus was observed on a standard medium to which either 6-(3-methyl-2-butenylamino)purine or 6-benzylaminopurine had been added (over a range of concentrations) and to which the other compounds (3-6) were also added in different concentrations. RESULTS AND DISCUSSIONThe combined effects of cytokinin and antagonist ...

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Cytokinins: Structure/activity relationships

Cited by 220 publications

References 47 publications

Effects of Cytokinins on Growth and Auxin in Coleoptiles of Derooted Avena Seedlings

Effects of Cytokinins on Growth and Auxin in Coleoptiles of Derooted Avena Seedlings

Modification of Logarithmic Growth Rates of Tobacco Callus Tissue by Gibberellic Acid

Cytokinins: Development of a Potent Antagonist

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