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1.
Effects of Thidiazuron on Cytokinin Autonomy and the Metabolism of N-(Delta-Isopentenyl)[8-C]Adenosine in Callus Tissues of Phaseolus lunatus L
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The effects of a highly cytokinin-active urea derivative, N-phenyl-N′-1,2,3-thiadiazol-5-ylurea (Thidiazuron), and zeatin on cytokinin-autonomous growth and the metabolism of N6-(Δ2-isopentenyl)[8-14C]adenosine ([14C]i6 Ado) were examined in callus tissues of two Phaseolus lunatus genotypes, cv Jackson Wonder and P.I. 260415. Tissues of cv Jackson Wonder maintained on any concentration of Thidiazuron became cytokinin autonomous, whereas only tissues exposed to suboptimal concentrations of zeatin displayed cytokinin-autonomous growth. Tissues of P.I. 260415 remained cytokinin dependent under all these conditions. The metabolism of [14C]i6 Ado was similar for the two genotypes, but differed with the medium used. [14C]i6 Ado was rapidly converted to N6-(Δ2-isopentenyl)[8-14C]adenosine 5′-P ([14C]i6 AMP) by tissues grown on zeatin-containing medium, whereas only traces of the nucleotide were formed in tissues grown on medium with Thidiazuron. Incubation with [14C] i6 AMP of tissues grown in the presence of Thidiazuron resulted in rapid conversion to [14C]i6 Ado, while [14C]i6 AMP persisted in tissues maintained on zeatin. Thus, Thidiazuron appears to stimulate enzyme activity converting the ribonucleotide to ribonucleoside. Although the cytokininactive phenylureas and adenine derivatives differ in their effects on cytokinin autonomy as well as nucleotide formation, the two types of effects do not seem to be related. 相似文献
2.
Regulation of Cytokinin Oxidase Activity in Callus Tissues of Phaseolus vulgaris L. cv Great Northern 总被引:6,自引:2,他引:4
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The regulation of cytokinin oxidase activity in callus tissues of Phaseolus vulgaris L. cv Great Northern has been examined using an assay based on the oxidation of N6-(Δ2-isopentenyl)adenine-8-14C (i6 Ade-8-14C) to adenine. Solutions of exogenous cytokinins applied directly to the surface of the callus tissues induced relatively rapid increases in cytokinin oxidase activity. The increase in activity was detectable after 1 hour and continued for about 8 hours, reaching values two- to three-fold higher than the controls. The cytokinin-induced increase in cytokinin oxidase activity was inhibited in tissues pretreated with cordycepin or cycloheximide, suggesting that RNA and protein synthesis may be required for the response. Rifampicin and chloramphenicol, at concentrations that inhibited the growth of Great Northern callus tissues, were ineffective in inhibiting the increase in activity. All cytokinin-active compounds tested, including both substrates and nonsubstrates of cytokinin oxidase, were effective in inducing elevated levels of the enzyme in Great Northern callus tissue. The cytokinin-active urea derivative, Thidiazuron, was as effective as any adenine derivative in inducing this response. The addition of Thidiazuron to the reaction volumes used to assay cytokinin oxidase activity resulted in a marked inhibition of the degradation of the labeled i6 Ade-8-14C substrate. On the basis of this result, it is possible that Thidiazuron may serve as a substrate for cytokinin oxidase, but other mechanisms of inhibition have not yet been excluded. 相似文献
3.
Cytokinin-Active Ribonucleosides in Phaseolus RNA: I. IDENTIFICATION IN tRNA FROM ETIOLATED PHASEOLUS VULGARIS L. SEEDLINGS
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The cytokinin-active ribonucleosides present in tRNA from etiolated Phaseolus vulgaris L. seedlings have been isolated and identified as cis-ribosylzeatin, 2-methylthio-ribosylzeatin, and N6-(Δ2-isopentenyl)-adenosine. The structures of the compounds were established on the basis of their chromatographic properties and the mass spectra of their permethylated and perdeuteromethylated derivatives. Cis-ribosylzeatin was the major cytokinin-active constituent of tRNA from this source. 相似文献
4.
Hajime Iwamura Toshio Fujita Shiro Koyama Koichi Koshimizu Zenzaburo Kumazawa 《Phytochemistry》1980,19(7):1309-1319
The substituent effect of N6-alkyl and -aralkyl adenines on the promotion of the growth of tobacco callus was analysed quantitatively using physico-chemical substituent parameters and regression analysis. The results indicated an optimum steric condition for activity in terms of the maximum width of the N6-substituents from the bond-axis connecting the N6-atom with its α carbon atom. The electron withdrawing effect of the N6-substituent enhances the activity. The substituent effect on the cytokinin activity of phenyl- and diphenyl- urea derivatives determined by Bruce and Zwar using the tobacco pith-block assay was also analysed. The results suggest that position-specific steric and hydrophobic effects of aromatic substituents participate in the variation in activity rationalizing the general trend of the activity; meta >para >ortho derivatives, for both series of compounds. The electronic effect is significant for the activity of diphenylureas but not for that of phenylureas which show somewhat different modes of interaction between the two series at the site of action. Based on inferences made from the correlations, hypothetical maps for the mode of interaction of these three sets of compounds at the site of action have been proposed. 相似文献
5.
Cytokinin structure-activity relationships and the metabolism of N-(delta-isopentenyl)adenosine-8-C in phaseolus callus tissues
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The activities of the free base and ribonucleoside forms of cytokinins bearing saturated and unsaturated N6-isoprenoid side chains have been examined in callus cultures derived from Phaseolus vulgaris cv. Great Northern, P. lunatus cv. Kingston, and the interspecific hybrid Great Northern × Kingston. In callus of cv. Great Northern, cytokinins bearing saturated side chains (N6-isopentyladenine, N6-isopentyladenosine, dihydrozeatin, and ribosyldihydrozeatin) were always more active than the corresponding unsaturated analogs (N6-[Δ2-isopentenyl]adenine, N6-[Δ2-isopentenyl]adenosine, zeatin, and ribosylzeatin). In callus of cv. Kinston, the cytokinins bearing unsaturated side chains were either more active or equally as active as the saturated compounds. These differences in cytokinin structure-activity relationships were correlated with differences in the metabolism of 14C-N6-(Δ2-isopentenyl)adenosine. In Great Northern tissues, this cytokinin was rapidly degraded to adenosine; in Kingston tissues, the major metabolite was the corresponding nucleotide. The growth responses of callus of the interspecific hybrid were intermediate between the parental tissues, and the metabolism of 14C-N6-(Δ2-isopentenyl)adenosine by the hybrid callus exhibited characteristics of both parental tissues. The results are consistent with the hypothesis that the weak activity of cytokinins with unsaturated side chains in promoting the growth of Great Northern callus is due to the rapid conversion of these cytokinins to inactive metabolites. 相似文献
6.
Soshiro Takahashi Koichi Shudo Toshihiko Okamoto Kumiko Yamada Yo Isogai 《Phytochemistry》1978,17(8):1201-1207
We have synthesized 35 N-phenyl-N′-(4-pyridyl)urea derivatives and tested their cytokinin activity in the tobacco callus bioassay. Among them, N-phenyl-N′- (2-chloro-4-pyridyl)urea is highly active, the optimum concentration of which is lower than 4 × 10?9 M (0.001 ppm), 3 compounds, i.e. N-(2-methylphenyl)-N′-(2-chloro-4-pyridyl)urea, N-(3-methylphenyl)-N′-(2-chloro-4-pyridyl)urea and N-(3-chlorophenyl)-N′-(2-chloro-4-pyridyl) urea are as active as N6-benzyladenine (concentration for optimum yield: 4.4 × 10?8 M or 0.01 ppm), and N-phenyl-N′-(2-methyl-4-pyridyl)urea and N-(2-chlorophenyl)-N′-(2-chloro-4-pyridyl)urea are as active as N-phenyl-N′-(4-pyridyl)urea (concentration for optimum yield: 4.7 × 10?7 M or 0.1 ppm), while the activity of the other 29 compounds are not so remarkable and 11 of them are almost or completely inactive. 相似文献
7.
Ruth Y. Schmitz Folke Skoog Adam Vincze Graham C. Walker Leslie H. Kirkegaard Nelson J. Leonard 《Phytochemistry》1975,14(7):1479-1484
The cytokinin activities of adenosine 3′,5′-monophosphate, N6,O2″-dibutyryladenosine 3′,5−'monophosphate, 8-bromoadenosine 3′,5′-monophosphate, N6-(Δ2-isopentenyl)adenosine 3′,5′-monophosphate, and N6-benzyladenosine 3′,5′-monophosphate were determined in the tobacco bioassay and compared with the activities of the corresponding non-cyclic nucleotides, nucleosides and bases of the N6-isopentenyl-substituted, N6-benzyl-substituted, 8-bromo-substituted, and unsubstituted adenine series. In each of these series the cytokinin activities in decreasing order were: bases ⪢ nucleosides ⪖ nucleotides > cyclic nucleotides. All members of the N6-isopentenyl- substituted and N6-benzyl-substituted series were highly active cytokinins, reaching maximum activity at concentrations of 1 μM or less, whereas, as expected, all members of the unmodified adenine series were inactive in the tested concentration ranges of up to 180 and 200 μM for adenosine and adenine, and 40 μM for the adenine nucleotides. Members of the 8-bromo-substituted adenine series were much weaker cytokinins than the N6-substituted adenine derivatives but showed activity in the same sequence starting at a concentration of about 5 μM. Thus, in the cases of 8-bromoadenosine 3′,5′-monophosphate and N6,O2′-dibutyryl-adenosine 3′,5′-monophosphate, both of which have been reported to promote cell division and growth of plant tissues, the cytokinin activity is related to the 8-bromo substituent and to the N6-butyryl substituent, respectively, rather than to the 3′,5′-cyclic monophosphate moiety. 相似文献
8.
Isogai Yo; Takahashi Soshiro; Miyake Shinji; Kawachi Emiko; Shudo Koichi; Okamoto Toshihiko 《Plant & cell physiology》1983,24(4):773-775
Three cytokinin-active ureas, N-phenyl-N'-(2-hydroxy-4-pyridyl)urea,N-2-methylphenyl- N'-(2-hydroxy-4-pyridyl)urea and N-pbenyl-N'-(6-hydroxy-4-pyridazinyl)urea,were found to have growth-stimulating activity in the rice seedlingtest. Their structure-activity relationships are discussed. (Received November 27, 1982; Accepted February 28, 1983) 相似文献
9.
K. N. Pandey T. R. Kemp P. S. Sabharwal R. A. Andersen 《In vitro cellular & developmental biology. Plant》1979,15(11):857-860
Summary Callus tissue ofHaworthia mirabilis Haw. was irradiated with60Co gamma rays. tRNA was isolated, hydrolyzed enzymatically, and cytokinin-active ribonucleosides were separated by Sephadex
LH-20 column chromatography and assayed with the tobaccocallus cytokinin bioassay. Three cytokinins were detected in tRNA
from irradiated tissue, two of which chromatographed with zeatin riboside and N6-(Δ2-isopentenyl)adenosine. The third cytokinin-active ribonucleoside was retained longer than the above compounds on the Sephadex
column and may be 2-methylthio-N6-(Δ2-isopentenyl)adenosine. Two cytokinins were detected in tRNA from nonirradiated tissue—those chromatographed with zeatin riboside
and N6-(Δ2-isopentenyl)adenosine. Relationships between cytokinins from tRNA and free cytokinins found in tissue earlier are discussed.
This is paper 78-10-124 of the Kentucky Agricultural Experiment Staton and is published with approval of the Director. 相似文献
10.
Kinetin incorporated into tobacco callus ribosomal RNA and transfer RNA preparations 总被引:5,自引:3,他引:2
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Kinetin, N6-furfuryladenine, was incorporated into tobacco (nicotiana tabacum L., var. Wis. No. 38) callus RNA isolated from rapidly growing tissue cultured in the presence of N6-furfuryladenine-8-14C or unlabeled kinetin. Approximately 0.7% of the radioactivity in the labeled kinetin added to the medium was recovered as N6-furfuryladenosine (fr6A) in the rRNA and tRNA preparations from the tobacco callus. The rRNA contained over 90% of these fr6 A moieties. The extent of kinetin incorporation was four times greater than that observed for N6-benzyladenine. The radiochemical purity of the recovered fr6 A was confirmed by three successive chromatographic purifications on Sephadex columns (LH-20 eluted with 35% ethanol, G-10 eluted with 20% ethanol, and LH-20 eluted with water). A cytokinin-active ribonucleoside with elution volumes corresponding to fr6 A was isolated from the tobacco callus rRNA preparation. This compound was analyzed by gas-liquid chromatography and rigorously characterized as N6-furfuryladenosine by gas-liquid chromatography-mass spectrometry of the trimethylsilyl derivative. 相似文献
11.
Approximately 500 urea derivatives and related compounds were tested for ability to retard leaf senescence as measured by chlorophyll retention in radish (Raphanus sativus) leaf discs. Of the 90 compounds found to be active, some had activity at 10?6 M of the same order as kinetin. There was a high correlation between ability to promote chlorophyll retention and initiation of cell division. Highly active compounds had a planar ring and a HNCONH bridge; substitution with a HNCSNH bridge reduced activity and all other tested arrangements of the bridge gave inactive compounds. Substitution of both amino hydrogen atoms on one or both sides of the bridge reduced or removed activity. Some N′-substituted phenyl ureas were highly active. Introduction of a N-phenyl ring to a N-phenyl urea increased activity except where one ring was substituted in the para position with chloro, bromo or iodo. The activities of symmetrical disubstituted ureas were generally less than the corresponding N-monosubstituted derivative. The results suggest that the receptor site for cytokinin activity is the same for senescence retadation and cell division initiation. 相似文献
12.
Diurnal variations in photosynthetic products and nitrogen metabolism in expanding leaves 总被引:9,自引:6,他引:3
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Steer BT 《Plant physiology》1973,51(4):744-748
Expanding leaves of Capsicum frutescens L. cv. California Wonder, Cucumis melo L. cv. Hales Best, and Citrus sinensis L. Osbeck cv. Washington Navel showed a marked diurnal periodicity in the incorporation of 14C from photosynthetically fixed 14CO2 into amino acids. Incorporation was virtually nil at the beginning of the photoperiod, reached a maximum in the 6th to 7th hour and decreased during the latter part of the photoperiod. In Capsicum frutescens this was apparently a reflection of the availability of reduced nitrogen controlled by the activity of nitrate reductase in the leaves. This also controlled the periodicity of the incorporation of 14C into fraction I protein. Possible control mechanisms and the relation of nitrogen metabolism to the periodicity of leaf expansion growth are discussed. 相似文献
13.
David Kopečný Pierre Briozzo Hana Popelková Marek Šebela Radka Končitíková Lukáš Spíchal Jaroslav Nisler Catherine Madzak Ivo Frébort Michel Laloue Nicole Houba-Hérin 《Biochimie》2010
Cytokinin oxidase/dehydrogenase (CKO) is a flavoenzyme, which irreversibly degrades the plant hormones cytokinins and thereby participates in their homeostasis. Several synthetic cytokinins including urea derivatives are known CKO inhibitors but structural data explaining enzyme–inhibitor interactions are lacking. Thus, an inhibitory study with numerous urea derivatives was undertaken using the maize enzyme (ZmCKO1) and the crystal structure of ZmCKO1 in a complex with N-(2-chloro-pyridin-4-yl)-N′-phenylurea (CPPU) was solved. CPPU binds in a planar conformation and competes for the same binding site with natural substrates like N6-(2-isopentenyl)adenine (iP) and zeatin (Z). Nitrogens at the urea backbone are hydrogen bonded to the putative active site base Asp169. Subsequently, site-directed mutagenesis of L492 and E381 residues involved in the inhibitor binding was performed. The crystal structures of L492A mutant in a complex with CPPU and N-(2-chloro-pyridin-4-yl)-N′-benzylurea (CPBU) were solved and confirm the importance of a stacking interaction between the 2-chloro-4-pyridinyl ring of the inhibitor and the isoalloxazine ring of the FAD cofactor. Amino derivatives like N-(2-amino-pyridin-4-yl)-N′-phenylurea (APPU) inhibited ZmCKO1 more efficiently than CPPU, as opposed to the inhibition of E381A/S mutants, emphasizing the importance of this residue for inhibitor binding. As highly specific CKO inhibitors without undesired side effects are of major interest for physiological studies, all studied compounds were further analyzed for cytokinin activity in the Amaranthus bioassay and for binding to the Arabidopsis cytokinin receptors AHK3 and AHK4. By contrast to CPPU itself, APPU and several benzylureas bind only negligibly to the receptors and exhibit weak cytokinin activity. 相似文献
14.
《Bioorganic & medicinal chemistry》2016,24(10):2318-2329
In the present study a series of urea and sulfamide compounds incorporating the tetralin scaffolds were synthesized and evaluated for their acetylcholinesterase (AChE), human carbonic anhydrase (CA, EC 4.2.1.1) isoenzyme I, and II (hCA I and hCA II) inhibitory properties. The urea and their sulfamide analogs were synthesized from the reactions of 2-aminotetralins with N,N-dimethylcarbamoyl chloride and N,N-dimethylsulfamoyl chloride, followed by conversion to the corresponding phenols via O-demethylation with BBr3. The novel urea and sulfamide derivatives were tested for inhibition of hCA I, II and AChE enzymes. These derivatives exhibited excellent inhibitory effects, in the low nanomolar range, with Ki values of 2.61–3.69 nM against hCA I, 1.64–2.80 nM against hCA II, and in the range of 0.45–1.74 nM against AChE. In silico techniques such as, atomistic molecular dynamics (MD) and molecular docking simulations, were used to understand the scenario of the inhibition mechanism upon approaching of the ligands into the active site of the target enzymes. In light of the experimental and computational results, crucial amino acids playing a role in the stabilization of the enzyme–inhibitor adducts were identified. 相似文献
15.
Angela Carra Maria Beatrice Del Signore Francesco Sottile Ada Ricci Francesco Carimi 《Plant Growth Regulation》2012,66(3):229-237
A protocol for in vitro multiplication of caper (Capparis spinosa L. subsp. rupestris) from nodal segments collected from mature plants was developed. For shoot multiplication, one auxin (indol-3-butyric acid,
IBA) and cytokinins of two different classes were used: the N6-substituted adenine derivatives 6-benzylamino purine (BAP),
and the two synthetic phenylurea derivatives N-phenyl-N′-benzothiazol-6-ylurea (PBU) and N-phenyl-N′-(1,2,3-thidiazol-5-yl) urea (thidiazuron, TDZ). Maximum shoot production was achieved from explants cultured with the adeninic
cytokinin BAP (4 μM) and the auxin IBA (0.5 μM). New shoots longer than 1 cm were used for rooting. To induce root formation,
three auxins [indole-3-butyric acid (IBA), 1-naphthaleneacetic acid (NAA) and 3-Indoleacetic acid (IAA)] and two synthetic
phenylurea derivatives [N,N-bis-(2,3-methylenedioxyphenyl)urea (2,3-MDPU) and N,N-bis-(3,4-methylenedioxyphenyl)urea (3,4-MDPU)] were used. All rooting compounds tested stimulated the formation of roots.
However, the best result in terms of a high percentage of rooted shoots having a well-developed root system with many lateral
roots was achieved with the synthetic phenylurea 2,3-MDPU (1 μM) with 93.7% of well rooted plantlets. About 80% of rooted
plantlets were successfully acclimatized and transferred to the greenhouse. 相似文献
16.
R Parthasarathy J M Ohrt G B Chheda 《Biochemical and biophysical research communications》1974,57(3):649-653
The crystal structure of the potassium salt of N-(purin-6ylcarbamoyl) glycine was determined from three-dimensional X-ray diffraction data. The N6-substituent is distal () to the imidazole ring, forming an intramolecular hydrogen bond N(glycine) -H---N(1)adenine. This conformation of the N6-substituent is typical of ureidopurines, and blocks the two sites N6-H and N1 of adenine that are normally utilized for complementary base-pairing in the double helical regions of nucleic acids; the internal hydrogen bonding further enhances the shielding of N1. This blocking of N6-H and N1 may be important in enhancing the single stranded conformation of the anticodon loop of tRNA and in preventing the modified adenosine adjacent to the anticodon from taking part directly in codon-anticodon interaction through the complementary base pairing. 相似文献
17.
Siragusa M Carra A Salvia L Puglia AM De Pasquale F Carimi F 《Plant cell reports》2007,26(8):1289-1296
Somatic embryos were regenerated in vitro from calamondin style–stigma explants cultured in the presence of N
6-benzylaminopurine (BAP) cytokinin and three synthetic phenylurea derivatives, N-(2-chloro-4-pyridyl)-N-phenylurea (4-CPPU), N-phenyl-N′-benzothiazol-6-ylurea (PBU) and N,N′-bis-(2,3-methilendioxyphenyl)urea (2,3-MDPU). The phenylurea derivative compounds tested at micromolar level (12 μM) were
able to induce a percentage of responsive explants significantly higher from that obtained with BAP and hormone-free (HF)
conditions. In order to verify the genetic stability of the regenerants, 27 plants coming from different embryogenic events
were randomly selected from each different culture condition and evaluated for somaclonal variations using inter-simple sequence
repeat and random amplified polymorphic DNA analyses. We observed that 2,3-MDPU and PBU gave 3.7% of somaclonal mutants, whereas
4-CPPU gave 7.4% of mutants. No somaclonal variability was observed when plantlets were regenerated in BAP or HF medium. Although
diphenylurea derivatives show a higher embryogenic potential as compared to BAP, they induce higher levels of somaclonal variability.
This finding should be taken in consideration when new protocols for clonal propagation are being developed. 相似文献
18.
《Mutation Research Letters》1995,346(2):99-105
Mutagenicity of 6-aminoquinoxaline derivatives was tested with Salmonella typhimurium strains Ta98 and TA100 in the presence and absence of S9 mix from the viewpoint that the 6-aminoquinoxaline skeleton is a common unit of mutagenic imidazoquinoxalines. We tested nine compounds: 5-methyl-6-methylaminoquinoxaline (1), 3,5-dimethyl-6-methylaminoquinoxaline (2), 2,5-dimethyl-6-metnylaminoquinoxaline (3), 6-methylamino-2,3,5-trimethylquinoxaline (4), 2,3-diethyl-5-methyl-6-methylaminoquinoxaline (5), 5-methyl-6-methylamino 3-phenylquinoxaline (6), 6-amino-2,3,5-trimethylquinoxaline (7), 6-dimethylamino-2,3-5-trimethylaminoquinoxaline (8), 6-amino-2,3-dimethylquinoxaline (9). These compounds showed the mutagenic activity for both TA98 and TA100 in the presence of S9 mix, where they were more sensitive for TA100 strain. Methyl groups at the 2, 3 and/or 5 positions increased the potency of mutagenicity (1 < 2 < 3 ⪡ 4, 9 < 7). However, ethyl groups at the 2 and 3 positions lowered the mutagenicity of the methyl substitute but elevated it of the parental compound (1 < 5 < 4). A methyl group at the N6 position decreased the mutagenicity (7 > 4 > 8). 相似文献
19.
Ana Isabel Martínez-Gómez Josefa María Clemente-Jiménez Felipe Rodríguez-Vico Liisa T. Kanerva Xiang-Guo Li Francisco Javier Las Heras-Vázquez Sergio Martínez-Rodríguez 《Process Biochemistry》2012,47(12):2090-2096
Taking advantage of the catalytic promiscuity of pyrimidine-catabolism enzymes (dihydropyrimidinase (E.C. 3.5.2.2), N-carbamoyl-β-alanine amidohydrolase (E.C. 3.5.1.6)), the production of different β-alanine derivatives starting from 5- and 6-monosubstituted dihydrouracils has been evaluated using a mimesis approach. In this work, the S-enantioselective character of dihydropyrimidinase from Sinorizhobium meliloti toward 6-monosubstituted dihydrouracil derivatives has been shown. An inverted R-/S-enantioselectivity of N-carbamoyl-β-alanine amidohydrolase from Agrobacterium tumefaciens toward two different N-carbamoyl-β-amino acids has been proved. Our results have shown for the first time that this mimetic tandem constitutes an interesting biotechnological tool for the preparation of different β-alanine derivatives in an environmentally friendly way, allowing the production of enantioenriched (R)-α-phenyl-β-alanine (e.e. > 95%) and (R)-α-methyl-β-alanine (e.e. > 90%). 相似文献
20.
Rhythmic Nitrate Reductase Activity in Leaves of Capsicum annuum L. and the Influence of Kinetin 总被引:3,自引:3,他引:0
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Steer BT 《Plant physiology》1976,57(6):928-932
In the expanding leaves of Capsicum annuum L. cv. California Wonder, two of the three peaks of nitrate reductase activity associated with the light period exhibit a circadian rhythm that persists in continuous light. 相似文献