Revised identification of the chromophore of a cell division factor from crown gall tumor cells of Vinca rosea L

Ribosyl-trans-Zeatin, A Major Cytokinin Produced by Crown Gall Tumor Tissue

A cell division factor in crystalline form has been isolated from ethanolic extracts of cultured Vinca rosea L. crown gall tumor tissue. The crystalline material shows the melting point, mass spectrum, ultraviolet-light absorbancy spectra, solubilities, chromatographic migration values, ion-exchange behavior, and growth activities expected of ribosyl-trans-zeatin, that is, 6-(4-hydroxyl-3-methyl-trans-2-butenylamino)-9-beta-D- ribofuranosylpurine. This compound, which appears to be a major cell-division factor in the extracts, has also been crystallized from liquid media in which the tumor tissue had been growing and apparently was the only active compound in such media.

8-bromoadenosine 3':5'-cyclic monophosphate as a promoter of cell division in excised tobacco pith parenchyma tissue

8-Bromoadenosine 3':5'-cyclic monophosphate, when used in association with an auxin, can completely replace the cell-division-promoting activity of either a cytokinesin or a 6-substituted adenylyl cytokinin in excised tobacco pith parenchyma tissue. The 8-bromo derivative of adenosine 3':5'-cyclic monophosphate was found to be far more resistant to degradation by plant adenosine 3':5'-cyclic monophosphate phosphodiesterases than was adenosine 3':5'-cyclic monophosphate. These findings appear to provide further support for the suggestion made earlier that the cytokinesins, which are potent inhibitors of both plant and animal adenosine 3':5'-cyclic monophosphate phosphodiesterases, exert their cell-division-promoting effects as regulators of adenosine 3':5'-cyclic monophosphate.

Reversal of the neoplastic state in plants

Crown-gall transformation involves the gradual and progressive activation of several biosynthetic capacities of the normal cell. These changes in cellular heredity, although extremely stable, are nonetheless potentially reversible and leave the cell totipotent. There is growing evidence that tumor-inducing principle is a self-replicating entity similar to a plasmid. Thus, it could be argued that tumor progression involves changes in the number or state of these entities in the cell. Studies of CDF habituation bear directly on this problem. Conversion of a cell division factor (CDF)-requiring normal cell to the CDF-autotrophic state is a key event in transformation. The fact that CDF habituation is progressive, occurs in the absence of agents of bacterial origin, and has an epigenetic basis indicates that it is not necessary to invoke either somatic mutation or the addition of foreign genes to account for tumor stability and progression in crown-gall. This conclusion provides further support for the hypothesis that, in the words of Braun,(78) "... the cancer problem is basically a problem of anomolous differentiation... Neoplastic growth, like developmental processes, stems from epigenetic modifications against a constant cellular genome."

Isoenzymes of acid phosphatase and non-specific esterases in cultures of neoplastic and normal tobacco tissues

Axenic cultures of normal, habituated and crown gall teratoma were grown under varying conditions to examine the effects of environment on the expression of neoplastic character. Acid phosphatase patterns on polyacrylamide gels did not vary greatly among tissues although there were differences in acid phosphatase activity between various strains of Agrobacterium tumefaciens, the bacteria which cause crown gall. Certain esterase isoenzymes were found only in tissues grown on specific media, while others were tissue-specific but independent of the nature of the medium. Comparisons of liquid and solid grown cultures revealed that culture conditions also influence esterase expression. Both sunflower and tobacco crown gall tissue contained an esterase not found in habituated or normal tissues, and similar in electrophoretic mobility to an esterase found in extracts of the bacteria that had induced the tumors. The basic difference between the three tissue types studied is the manner in which they respond to a given environment.

Cell-division factors from Vinca rosca L. crown gall tumor tissue

A cell-division factor has been precipitated from extracts of cultured Vinca rosea L. crown gall tumor tissue by using the mercuric acetate procedure previously employed by Wood and colleagues to obtain their "cytokinesin I." On the basis of its mass spectrum, ultraviolet light absorbancy spectra, solubilities, chromatographic migration values, and growth activity, the factor is ribosyl-trans-zeatin, that is, 6-(4-hydroxy-3-methyl-trans-2-butenylamino)-9-beta-D-ribofuranosylpurine. Ribosylzeatin has now been isolated from tumor tissue by four experimental techniques; any possibility that it is an artifact seems to have been eliminated. Contrary to the report by Wood and colleagues, synthetic ribosylzeatin is precipitated from an aqueous solution by mercuric acetate, provided the complete precipitation procedure is utilized. These facts and others discussed strongly support our suggestion that ribosylzeatin was present in the preparation ("cytokinesin I") examined by Wood and colleagues in several biological assays. The reasons advanced by Wood and others for rejecting this suggestion have been found either not to be pertinent to the question or to have insufficient experimental bases.

Comparative Activity of Isomers of Zeatin and Ribosyl-Zeatin on Funaria hygrometrica

The activities of isomers of zeatin, ribosyl-zeatin, and 6-(gamma,gamma-dimethylallylamino) purine (i(6)Ade) on the moss Funaria hygrometrica are compared by measuring the ability of the cytokinins to induce callus or gametophores. The cis- and trans-ribosyl-zeatins were inactive, and therefore this kind of bioassay cannot be used as evidence for the presence or absence of a cytokinin in tests on natural products.

A comparative study of cytokinesins I and II and zeatin riboside: a reply to Carlos Miller

Two cell-division-promoting factors, which have partition coefficients of 1.9 and 2.75 determined by 500-tube countercurrent distribution in a butanolwater system, have been repeatedly isolated in this laboratory from crown gall tumor tissues of Vinca rosea L. These substances have been given the trivial names cytokinesin I and cytokinesin II, respectively. Chemical and mass spectrometric analyses suggest that both cytokinesins are substituted hypoxanthines and are thus very different compounds from the 6-substituted adenyl cytokinins. Carlos Miller, using a very different and far more drastic isolation procedure, obtained one main cell-division-promoting factor from these same tumor tissues, which he identified as ribosyl-trans-zeatin. On the basis of this finding, and without an attempt to repeat our studies, questions have been raised by Miller concerning the existence of the cytokinesins as biologically active substances. We have, therefore, compared some pertinent physical, chemical, and biological properties of the cytokinesins with those of zeatin riboside, have demonstrated that these three substances can be cleanly separated from one another by a number of different methods and that each behaves as a pure substance in the several systems, and, finally, we have shown that the cytokinesins are not contaminated with ribosyl-trans-zeatin and thus do not owe their biological activity to such a contaminant.

Bud formation in Funaria hygrometrica: A comparison of the activities of three cytokinins with their ribosides

The activities of the cytokinins benzyladenine (BA), 6-(3-methylbut-2-enylamino)purine (IPA) and zeatin in promoting bud formation in protonemata of Funaria hygrometrica (L.) Sibth. were compared to the biological activities of the corresponding ribosides. Cytokinins were found to have considerably higher hormonal activity as free bases than as ribosides. This observation will be discussed in relation to the chemical identity of the celldivision factor (CDF) isolated from crown gall tumors of Vinca rosea L.

The inhibition of plant and animal adenosine 3':5'-cyclic monophosphate phosphodiesterases by a cell-division-promoting substance from tissues of higher plant species

One member of a new class of cell-division-promoting factors, that has been given the trivial name of cytokinesin I, is a potent inhibitor of adenosine 3':5'-cyclic monophosphate phosphodiesterases of both plant and animal origin. Since an adenylate cyclase has been demonstrated in this study to be present in plant cells, the results suggest that cytokinesin I may be exerting its biological effects in promoting division in cells of higher plant species as a regulator of adenosine 3':5'-cyclic monophosphate.