Cytokinins: Distribution in Species of Yeast Transfer Rna

Armstrong, Donald J.; Skoog, Folke; Kirkegaard, Leslie H.; Hampel, Arnold; Bock, Robert M.; Gillam, I. C.; Tener, G. M.

doi:10.1073/pnas.63.2.504

Cited by 44 publications

(15 citation statements)

References 24 publications

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“…(1). Nevertheless, the tRNAleu may be suspected of harboring a cytokinin also in yeast, as here again the rule could apply that the presence of cytokinins is restricted to tRNA species for which the corresponding codon starts with U, and this includes tRNAleu but excludes tRNAval (2). An experiment using leucine and tyrosine is detailed in Table Viii. and another, using valine and tyrosine in Table IX. A relative stimulation of tyrosine incorporation in a kinetin (19).…”

Section: Resultsmentioning

confidence: 99%

Action of Kinetin on Cotyledons of Fenugreek

Rijven

Parkash

1971

Plant Physiol.

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Isolated cotyledons of fenugreek (Trigonella foenum graecum L.), which respond rapidly and specifically to the application of cytokinins with stimulated expansion, have been used to study the primary action of kinetin. Gross chemical analysis showed that ribonucleic acid increased within 24 hours in response to kinetin application. 8-Azaguanine inhibited both kinetin-induced expansion and RNA synthesis; 5-fluorodeoxyuridine inhibited only the RNA synthesis.Cotyledons produced nitrate reductase activity in response to 20 mm nitrate only in the presence of either light or kinetin and especially in the presence of both. Abscisic acid and inhibitors of RNA and protein synthesis depressed this response. Inhibitors affecting chloroplast development and function did not reduce the response in the presence of light and kinetin.In vitro incorporation of 14C-L-leucine and '4C-L-phenylalanine into protein by various recombinations of microsomal and 160,000g supernatant fractions varied according to the pretreatment which the cotyledons had received before the preparation of the fractions. Stimulatory effects were mainly associated with the microsomal fractions.The formation of leucine-, valine-, and tyrosine-tRNA complexes by high speed supernatant fractions from differently pretreated cotyledons was also compared. The sharp stimulation of the process by adding tRNA was found to be independent of the kind of preincubation that the cotyledons used for the tRNA extraction had received. radioactivity from benzyladenine, applied to a tissue, could be recovered from its RNA mostly in the tRNA fraction. Also, some of the radioactivity of the acid hydrolysate of this fraction traveled on the chromatogram as benzyladenine. However, the crucial evidence that applied cytokinins in a responsive tissue do, in fact, promptly correct some specific tRNA deficiency, i.e., that of serine or tyrosine, is still lacking.Our data, relevant to the tRNA hypothesis, are presented in the later section of "Results" reporting the outcome of recombinations of parts of the protein-synthesizing machinery from control and kinetin-treated cotyledons. They are difficult to reconcile with the tRNA hypothesis, at least in its most naive form. Whatever the primary action of kinetin, the evidence presented suggests that in cotyledons, as a consequence of that action, a less specific activation of nucleic acid synthesis occurs. MATERIALS AND METHODSPreparation of Cotyledons. The cotyledons of fenugreek (Trigonella foenum graecum L.) can be separated from the embryonic axis by a cut through the dry seed, as the space between these parts is indicated by a groove in the seed exterior. Further manipulations-sterilization and washing of cut seeds, their transfer onto wet filter paper in Petri dishes, removal of seed coats 20 hr later, weighing and layering of cotyledons-were done in green safelight. Usually cotyledons were arranged in a 7-cm Petri dish containing one filter paper disc to which was added 3 ml of test solution containing 1 mg each of mycostat...

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Section: Resultsmentioning

confidence: 99%

Action of Kinetin on Cotyledons of Fenugreek

Rijven

Parkash

1971

Plant Physiol.

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“…The quantities of cytokinin were calculated from the Xma, absorbances and the known extinction coefficients of the ribonucleosides (23). Purified cytokinin-active ribonucleosides were trimethylsilylated as described (18). Gas/liquid chromatophy-mass spectrometry of trimethylsilylated cytokinins was performed on a Varian aerograph series 2700 gas chromatograph coupled via a glass jet separator to a model 21-491B DuPont Instruments mass spectrometer equipped with oscillograph.…”

Section: Methodsmentioning

confidence: 99%

“…Cytokinins were purified from the supernatant fraction as described (5). Cytokinin activity was determined by the tobacco callus bioassay (18,19) and is expressed as ,ug of kinetin equivalents (KE) [,ug of kinetin (6-furfurylaminopurine) required -to give the same growth response as the test sample under the specified bioassay conditions].…”

Section: Methodsmentioning

confidence: 99%

Relationships between cytokinin production, presence of plasmids, and fasciation caused by strains of Corynebacterium fascians

Murai

Skoog

Doyle

et al. 1980

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

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Cytokinin activity in the culture medium of four pathogenic strains of Corynebacterium fascians varied from 168 to 0.4 jsg of kinetin (6-furfurylaminopurine) equivalents per liter, as compared to 0.2 in an avirulent control. NA-Isopentenyladenine was the predominant cytokinin in the medium of all five strains, and its increased production was correlated with the degree of pathogenicity; however, the virulent strains also produced 8-13 times more cis-zeatin [6(4-hydroxy-3-methyl-cis-2-butenylamino)purineJ than the avirulent strain. as 644-hydroxy-3-methyl-cis-2-butenylamino)9-0-D-ribofuranosylpurine, 6q3methyl-2-butenylamino.9-j-D-ribofuranosylpurine, and their 2-methylthio derivatives. The fifth cytokinin was tentatively identified as 6(4-hydroxy-3-methyl-trans-2-butenylamino)9-#-D-ribofuranosylpurine. Ribosyl-cis-zeatin was 3fold higher and N6-isopentenyladenosine was correspondingly lower in the plasmid-containing strains than in the plasmidless control. Because the entire syndrome of fasciation caused by infection can be induced with synthetic cytokinins, the disease would appear to be caused by plasmid-induced high rates of cytokinin production by the bacteria. Corynebacterium fascians causes fasciation disease or witches' broom in dicotyledonous plants. The disease is characterized by release of apical dominance and outgrowth of lateral buds, which gives rise to the characteristic witches' broom syndrome (1). The symptoms of the disease can be duplicated by treatment of seeds or seedlings with cytokinins, indicating that it may be caused by cytokinins produced by the microbe (2). From C. fascians culture medium four cytokinins, 6-(3-methyl-2-butenylamino)purine. (i6Ade), 6-(4-hydroxy-3-methyl-cis-2-butenylamino)purine (c-io6Ade), 6-(4-hydroxy -3-methyl-cis -2-butenylamino) -2-methylthiopurine (ms2-c-io6Ade), and 6-methylaminopurine (m6Ade),.have been characterized, and three additional cytokinins, 6-(4-hydroxy-3-methyl-trans-2-butenylamino)purine (t-io6Ade), 6-(4-hydroxy-3-methyl-2-butenylamino)-9-/3-D-ribofuranosylpurine (io6A), and 6-(3-methyl-2-butenylamino)-9-f3-D-ribofuranosylpurine (i6A), have been tentatively identified (3-6). The tRNA of the bacterium has been reported to contain several cytokinins (7-9), but only c-io6A has been rigorously identified (10). Biosynthesis of the i6A moiety in tRNA involves the transfer of isopentenyl from A2-isopentenyl pyrophosphate to specific adenosine residues in preformed tRNA (11,12), and it has been proposed that i6Ade and other free cytokinins in the culture medium derive from tRNA degradation. The existence of alternative pathways is probable, as suggested by the in vitro synthesis of free i6Ade from AMP and A2-isopentenyl pyrophosphate recently achieved with an enzyme preparation from Dictyostelium (13). 619This report deals with the kinds and quantities of cytokinins released into culture media and present in tRNA of five strains of C. fascians, ranging from highly virulent to avirulent, and examines relationships of the presence of plasmids to cyto...

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“…Thus, the role of Ado-CO-thr in the molecular architecture parallels that of N6-(zA'-isopentenyl)adenosine. This nucleoside occurs adjacent to the 3' end of the anticodon of those molecular species responding to codons with first letter U (2,3).…”

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confidence: 99%