On the Significance of Cytokinin Incorporation into RNA

Kende, Hans; Tavares, James E.

doi:10.1104/pp.43.8.1244

Cited by 61 publications

(14 citation statements)

References 20 publications

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“…Criticism of the tRNA hypothesis has also been forthcoming from application of cytokinin analogues that cannot be incorporated into nucleic acid (10,14). The diphenyl ureas (4) would also present great difficulty in this respect.…”

Section: C-phenylalaninementioning

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: C-phenylalaninementioning

confidence: 99%

Action of Kinetin on Cotyledons of Fenugreek

Rijven

Parkash

1971

Plant Physiol.

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“…Dyson (8) and Srivastava (31) into both tRNA and rRNA, whereas Hall (16), Richmond et al (26), and Bezemer-Sybrandy et al (3) failed to detect any incorporation into RNA. Kende and Tavares (18), on the basis of measurements of incorporation of radioactive 6-benzylaminopurine and 6-benzylamino-9-methylpurine into soybean callus, claim that the methyl substituent in the 9 position inhibited incorporation of the latter cytokinin into RNA without inhibiting its biological activity. The validity of this report is subject to limitations in procedures employed.…”

mentioning

confidence: 99%

The Mode of Incorporation of 6-Benzylaminopurine into Tobacco Callus Transfer Ribonucleic Acid

et al. 1974

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“…This study has shown that s-triazine compounds, at very low concentrations, possess activity other than auxin-like which enhances sorghum callus growth, in the absence of other cytokinin sources in the medium. Regardless of their chemical structure, cytokinins are known to be substances capable of causing cell proliferation (1,7). Cytokinins were also reported to cause an increase in protein synthesis in the plant tissue (2,8,9,(22)(23)(24).…”

Section: Resultsmentioning

confidence: 99%

Promotion of Sorghum Callus Growth by the s-Triazine Herbicides

Nadar

Clegg²,

Maranville³

1975

Plant Physiol.

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Growth-promoting action of simazine and other s-triazine herbicides was detected by the use of sorghum (Sorghum bicolor Several studies over a wide spectrum of economic crops showed that the application of the s-triazine herbicides (mainly simazine) to plants at sublethal levels may cause an increase in total protein content as well as alteration of certain biological activities such as nitrate reductase (17,18,21,26). Since all known cytokinin active compounds are found to be nucleotide derivatives (4, 5, 10, 11), and the s-triazine ring is pyrimidine-like in structure with the number 5 carbon atom replaced by a nitrogen atom, it is possible that the action of the s-triazines in increasing protein content is due to alteration in hormonal control similar to that caused by kinetin.No chemical method has been developed to detect cytokinins easily. There are many biological assay systems to detect them, of which the callus tissue system may be the most reliable (13). Sorghum callus tissue developed in our laboratories from the hybrid RS 671 grain sorghum (Sorghum bicolor [L]. Moench) was dependent on an external source of cytokinin, which made it an excellent material to use in bioassays to detect the suspected growth-promoting action of the s-triazines. This paper reports that the effect of sublethal levels of simazine and other s-triazines Soil applications of simazine were made to the containers 2.5 cm below the surface by removing the top 2.5 cm of soil, spraying the calculated dose suspended in sufficient amount of water, and then replacing the soil. The dose was calculated as a fraction of the recommended field application rate corresponding to the area of the container surface. The soil treatments of simazine were added at concentrations 0.25, 0.5, 0.75 and 1.00 times the recommended amounts for application as a herbicide in the field (1.12 kg/ha). The application took place immediately prior to planting. A foliar application was administered 4 weeks after planting at concentrations 0.25, 0.5, 0.75 and 1.00 times the simazine saturated solution of S ,ug/ml (25). The plants were sprayed once until completely soaked with the solution.Root Exudate Sampling. The aerial portions of the plants were removed 3.5 cm above the soil surface and a piece of parafilm rolled around the stubs which extended above the cut surfaces. The exudates were collected periodically by means of a syringe until 5 to 10 ml was accumulated from each exuding plant. The exudates were filtered through Whatman No. 1 filter paper and added to the callus growth medium to test for their growthpromoting action.Testing for Growth Promotion. Callus was induced from hybrid RS 671 on Murashige and Skoog medium (15) supplemented with 2 to 5 jAg/ml of 2,4-D and 1% (v/v)

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On the Significance of Cytokinin Incorporation into RNA

Cited by 61 publications

References 20 publications

Action of Kinetin on Cotyledons of Fenugreek

Action of Kinetin on Cotyledons of Fenugreek

The Mode of Incorporation of 6-Benzylaminopurine into Tobacco Callus Transfer Ribonucleic Acid

Promotion of Sorghum Callus Growth by the s-Triazine Herbicides

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