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1.
The embryos of germinating Zea mays seed were supplied with[14C]-adenine Following incubation, the tissue was extractedand extensively purified by non-exchange chromatography andthin layer chromatography. Radioactivity was found to be incorporatedinto zeatin nucleotide indicating that the embryo in the germinatingseed is capable of cytokinin biosynthesis. Key words: Zea mays cytokinin, zeatin nucleotide, biosynthesis, seed 相似文献
2.
High specific activity [3H]-zeatin riboside (ZR) was suppliedto germinating seed and developing seedlings of Zea mays tostudy its metabolism and translocation The major metabolitesof ZR in endosperm, embryo, and first leaves were adenosine,adenine, and adenine nucleotide When ZR was supplied to theradicle tip a significant proportion of the radioactivity extractedfrom the radicle was identified as zeatin-9-glucoside (Z9G).However, some ZR was also transported to the shoot and vestigialembryo During the initial stage of germination, movement ofzeatin riboside from the embryo to the endosperm was pronouncedbut little movement occurred in the reverse direction Key words: Zea mays cytokinin, zeatin riboside, metabolism, translocation 相似文献
3.
The viability of seeds is associated with ageing and storageconditions. A loss of viability is accompanied by slow germination,reduced growth, and a decline in protein and poly(A)+RNA synthesis.This paper reports on the activity of poly(A) polymerase indry and germinating embryos of Triticum durum Desf. cv. Cappellicaryopses of different ages and viability. The enzyme was presentas a single form during ageing and germination. The poly(A)polymerase was active at decreasing levels in all aged dry embryos,in parallel with loss of viability. Its activity strongly increasedduring the germination only in viable embryos. The observedincrease was due to de novo synthesis of the enzyme. Poly(A)polymerase synthesis was low during germination of less viableembryos and absent in older ones. Reduced poly(A) polymeraseactivity in dry or germinated wheat embryos may cause a shorteningof poly(A) chains in vitro and a decline in poly(A)+RNA synthesis.Copyright1995, 1999 Academic Press Triticum durum Desf. cv. Cappelli, wheat, embryo, natural ageing, poly(A) polymerase 相似文献
4.
Changes in the activity of adenine and guanine salvage in nucleotideand nucleic acid synthesis during the growth of Catharanthusroseus were investigated. Incorporation of [8-14C]adenine intoATP and ADP and that of [8-14C]guanine into GTP and GDP increasedmarkedly in the lag phase of cell growth and then sharply decreased.The incorporation into RNA from both precursors showed a similarpattern. The role of rapid purine salvage observed in the lagphase of cell growth is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture cells, purine salvage, adenine, guanine 相似文献
5.
Biosynthesis of Caffeine in Flower Buds of Camellia sinensis 总被引:1,自引:0,他引:1
The biosynthesis of purine alkaloids in flower buds of tea plantswas investigated. More than 25% of total radioactivity of [8-14C]adeninetaken up by stamens isolated from tea flower buds was foundto have been incorporated into purine alkaloids, namely, theobromineand caffeine, 24 h after administration of the labelled compound.Pulse-chase experiments indicated that [8-14C]adenine takenup by the stamens was converted to adenine nucleotides and subsequentlyincorporated into theobromine and caffeine. Since 5 µMcoformycin, an inhibitor of AMP deaminase, inhibited the incorporationof radioactivity into the purine alkaloids, synthesis of caffeinefrom adenine nucleotides seems to be initiated by the reactionof AMP deaminase. Although most of the radioactivity from [8-14C]inosinewas recovered as CO2 and ureides, considerable amounts of radioactivitywere recovered as purine alkaloids. The incorporation of radioactivityfrom [8-14C]inosine into the purine alkaloids was not affectedby coformycin. The five enzymes involved in synthesis of 5-phosphoribosyl-1-pyrophosphatefrom glucose were present in the stamens and petals of tea flowerbuds. From present and previous results, the pathway for thebiosynthesis of caffeine from adenine nucleotides in flowerbuds of tea is discussed.Copyright 1993, 1999 Academic Press Camellia sinensis, tea, stamen, flower, biosynthesis, purine alkaloids, caffeine, theobromine, adenine nucleotides, nucleotide biosynthesis 相似文献
6.
Jespersen Anne-Mette; Nielsen Jan; Riemann Bo; Sondergaard Morten 《Journal of plankton research》1992,14(5):637-648
Measurements of biomass and growth rate of two axenic algalcultures were carried out using three different methodologicalapproaches: the specific 14C-labelling of chlorophyll a, [3H]adenineincorporation into DNA and net organic carbon assimilation.Time-course experiments revealed that the specific activitiesof chlorophyll a were significantly higher than the specificactivity of total algal carbon in six of seven experiments.When the specific activity of chlorophyll a is used to calculatethe carbon biomass and growth rate, the carbon biomass of thealgae will thus be underestimated and the specific growth ratewill be too high. Determination of growth rates from incorporationof [3H]adenine gave lower values than those obtained from netorganic carbon assimilation and from 14C incorporation intochlorophyll a. Problems with adenine saturation are suggested.When [3H]adenine is used to measure growth rates in dense algalcultures, additions of >1 µM [3H]adenine are oftenrequired to maximally label the extracellular and intracellularadenine pools and hence DNA. 相似文献
7.
Cycloheximide (2·0 µg ml1) inhibits theincorporation of [14C]phenylalanine and [14C]adenine into insolublecompounds in Ankistrodesmus braunii. 6-Methylpurine (1·0mM) inhibits only the incorporation of [14C]adenine and it isconcluded that it inhibits RNA synthesis. When ammonium-growncells of Ankistrodesmus or Chlorella are nitrogen-starved orwhen ammonium-grown cells of Dunalitlla are resuspended in nitratemedium, the appearance of nitrate reductase in these organismsis not inhibited by 6-methylpurine. The appearance of nitratereductase activity in Ankistrodesmus or Chlorella is inhibitedby 6-methylpurine when ammonium-grown organisms are preincubatedwith this substance for 1-2 h before nitrogen starvation. Itis concluded that cells growing with ammonium and lacking nitratereductase activity nevertheless contain preformed mRNA for nitratereductase synthesis. 相似文献
8.
Biosynthesis of Purine Alkaloids in Camellia Plants 总被引:2,自引:0,他引:2
The metabolism of [8-14C]adenine and [8-14C]hypoxanthine infour species of Camellia plants was investigated in relationto the synthesis of purine alkaloids, caffeine and theobromine.Young leaves of C. sinensis had the ability to synthesize caffeine,but in C. irrawadiensis, these labelled precursors were incorporatedinto theobromine, not caffeine. No synthesis of purine alkaloidscould be detected in C. japonica and C. sasanqua leaves. Conventional"salvage" and degradation pathways of purines were present inall species of Camellia plants examined.
1 Present address: Research Center, Mitsubishi Chemical IndustriesLtd., 1000 Kamisida-cho, Midori-ku, Yokohama, 227 Japan. (Received September 29, 1986; Accepted January 22, 1987) 相似文献
9.
Li W Nakagawa T Koyama N Wang X Jin J Mizuno-Horikawa Y Gu J Miyoshi E Kato I Honke K Taniguchi N Kondo A 《Glycobiology》2006,16(10):1007-1019
Alpha1,6-fucosyltransferase (Fut8) plays important roles inphysiological and pathological conditions. Fut8-deficient (Fut8/)mice exhibit growth retardation, earlier postnatal death, andemphysema-like phenotype. To investigate the underlying molecularmechanism by which growth retardation occurs, we examined themRNA expression levels of Fut8/ embryos (18.5days postcoitum [dpc]) using a cDNA microarray. The DNA microarrayand real-time polymerase chain reaction (PCR) analysis showedthat a group of genes, including trypsinogens 4, 7, 8, 11, 16,and 20, were down-regulated in Fut8/ embryos.Consistently, the expression of trypsinogen proteins was foundto be lower in Fut8/ mice in the duodenum, smallintestine, and pancreas. Trypsin, an active form of trypsinogen,regulates cell growth through a G-protein-coupled receptor,the proteinase-activated receptor 2 (PAR-2). In a cell culturesystem, a Fut8 knockdown mouse pancreatic acinar cell carcinoma,TGP49-Fut8-KDs, showed decreased growth rate, similar to thatseen in Fut8/ mice, and the decreased growth ratewas rescued by the application of the PAR-2-activating peptide(SLIGRL-NH2). Moreover, epidermal growth factor (EGF)-inducedreceptor phosphorylation was attenuated in TGP49-Fut8-KDs, whichwas highly associated with a reduction of trypsinogens mRNAlevels. The addition of exogenous EGF recovered c-fos, c-jun,and trypsinogen mRNA expression in TGP49-Fut8-KDs. Again, theEGF-induced up-regulation of c-fos and c-jun mRNA expressionwas significantly blocked by the protein kinase C (PKC) inhibitor.Our findings clearly demonstrate a relationship between Fut8and the regulation of EGF receptor (EGFR)-trypsin-PAR-2 pathwayin controlling cell growth and that the EGFR-trypsin-PAR-2 pathwayis suppressed in TGP49-Fut8-KDs as well as in Fut8/mice. 相似文献
10.
The combined application of 106 M adenine and 106M mevalonic acid to soya bean callus accelerated its growth.Two biologically active compounds that co-chromatographed withzeatin and isopentenyl adenine were extracted from this callus.Studies with labelled adenine and mevalonic acid indicated thatthe cytokinin-dependent soya bean callus incorporated only avery small amount of the radioactive precursors into the biologically-activecompounds, making it extremely difficult to determine whetherthese compounds were synthesized de novo or whether they aroseas by-products of tRNA turnover. As cytokinins do not accumulatein rapidly-growing cytokinin-dependent soya bean callus culturedon kinetin as a source of cytokinin it seems as if biosynthesisde novo occurs when the callus is supplied with adenine andmevalonic acid. Glycine max (L.) Merrill, soya bean, callus culture, adenine, mevalonic acid, endogenous cytokinins 相似文献
11.
The effects of different concentrations of L--aminooxy-ß-phenyIpropionicacid (AOPP), an analog of L-phenylalanine, on the activity ofphenylalanine ammonia-lyase (PAL, EC 4.3.1.5
[EC]
) and the growthof radicles in 24 h old germinating lettuce (Lactuca salivaL.) seeds were investigated. AOPP causes a significant inhibitionof PAL activity in the seeds (85% inhibition at 104 M). It alsocauses a stimulation of radicle growth at that concentration.The results show that the inhibition of PAL by AOPP may be dueto an irreversible binding of the inhibitor to the enzyme leadingto its inactivation. AOPP also inhibits ethylene biosynthesisin germinating lettuce seeds which could probably explain thestimulation of radicle growth in these seeds. The enzyme shows typical Michaelis-Menten kinetics. The Km forL-phenylalanine is 4.2 x 105 M. The enzyme does not show anytyrosine ammonia-lyase activity. Various substrate analogs suchas D-phenylalanine, p-fluorophenylalanine, ß-phenyllacticacid, tryptophan and the product of the enzyme reaction, trans-cinnamicacid, inhibit the enzyme competitively. A number of intermediatesand endproducts of the phenylpropanpid pathway, except chlorogenicacid, do not show any inhibition.
1Scientific contribution number 1423 from the New HampshireAgricultural Experiment Station. (Received May 9, 1986; Accepted September 8, 1986) 相似文献
12.
Adventitious plantlets were obtained from lateral buds, shoottips, embryos, and pieces of stem and rachilla tissue of Phoenixdactylifera L. cultured on a modified Murashige and Skoog mediumcontaining 3 mg l1 N-(2-isopenty)adenine 0?1100mg l1 -naphthaleneacetic acid or 2,4-dichlorophenoxyaceticacid, and 3 g l1 activated charcoal. Additions of auxinswere necessary to induce explants to produce callus, adventitiousplantlets, and roots. Plantlets were obtained from explantscultured 34 months in vitro. No difference in growthresponses between male and female explants was observed duringculture. Complex addenda of activated charcoal and polyvinylpyrrolidonewere tested in the nutrient media at various concentrationsto prevent explant browning. Activated charcoal fostered satisfactorygrowth by reducing the browning and inhibition of growth ofexplants. 相似文献
13.
A cytokinin-binding protein complex was purified 700-fold fromleaves of tobacco (Nicotiana sylvestris). The purification procedureconsisted of four chromatographic steps on columns of DEAE-cellulose,Mono Q, Phenyl Superose and Superose 12, respectively. The purifiedcytokinin-binding protein complex behaved as a 130-kDa globularprotein on gel filtration. This complex contains two proteinspecies whose molecular masses are estimated to be 57 kDa and36 kDa. Binding to benzyl[8-14C]adenine was inhibited by adenine,ATP, zeatin and cAMP but not by indoleacetic acid. Scatchardanalysis indicated the existence of at least two cytokinin-bindingsites in the purified complex. The dissociation constant forthe high-affinity site was 2.1 10-5 M. (Received October 19, 1992; Accepted February 27, 1993) 相似文献
14.
An Analysis of Seed Development in Pisum sativum: IV. COTYLEDON CELL POPULATIONS IN VIVO AND IN VITRO 总被引:1,自引:0,他引:1
AMBROSE M. J.; WANG T. L.; COOK S. K.; HEDLEY C. L. 《Journal of experimental botany》1987,38(11):1909-1920
A method for quantifying changes in the cell population of Pisumsativum cotyledons during development is described. The methodis based on determining the frequency distribution for cellarea following the random sampling of a single-cell suspensionof cotyledon cells. The population profile of these cells changedprogressively and systematically from a single population, similarin size to meristematic cells, found in embryos less than 3.0mg in fresh weight, to a bimodal population in embryos greaterthan 100 mg fresh weight. This method was used to compare embryosof similar size from two genotypes near-isogenic except forgenes at the r locus. No significant differences were foundbetween the cell population profiles of embryos up to 30 mgfresh weight. However, a significant difference was found betweenembryos with fresh weights of 100 mg, the wrinkled (rr) linehaving a higher mean and maximum cell area (2 951 µm2and 9 240 µm2 respectively) than the round (RR) line (2591µm2and 6470 µm2respectively). Comparisons were alsomade between cotyledon cell populations from round (RR) embryosgrown in vivo and in vitro. The most obvious differences werethe higher mean and maximum cell size of the large cell populationof in vitro grown embryos which were twice those found in vivo.Embryos grown to either 30 mg or 100 mg fresh weight in vitrohad a much greater proportion of large cells in the populationwith a corresponding reduction in total cotyledon cell number,compared with similar sized embryos grown in vivo. These data suggest that comparisons between different genotypes,or, between cultured and in vivoembryos, based on morphologicalsimilarities between embryos, may be invalid and subject tomisinterpretation. Key words: Pea, seed development, cell population 相似文献
15.
The application of 8[14C]t-zeatin to the radicle tips of germinatingPhaseolus vulgaris seeds revealed that cytokinins are transportedrapidly from the embryonic axis to the cotyledons, and are utilizedand metabolized extensively in these organs. The informationobtained on the transportation between the different parts ofthe embryo is consistent with the view that the mobilizationof food reserves from the cotyledons is controlled by cytokininswhich originate in the embryonic axis. Tentative identificationof the radioactive metabolites formed indicate that the appliedzeatin was altered by side-chain cleavage and by substitutionto the adenine ring. Phaseolus vulgaris, bean, germination, cytokinins, transport, radicle 相似文献
16.
The movement of kinetin has been investigated in roots of Zeaseedlings, grown in the dark, using kinetin-8-14C. Segments (10 and 11 mm) with and without an apex were used andthe following results obtained: The transport of kinetin is polarized basipetally. Kinetin-8-14C is transported in roots without vascular tissue,but the amount transported is always lower than in roots withvascular tissue. Thin-layer chromatography showed that the molecule of kinetinis metabolized in the root segments, adenine being one of theproducts. 相似文献
17.
Protease, peptidase, and ribonuclease activities were demonstratedin germinating pea cotyledons and axis tissues. These activitiesindicate that the enzymatic machinery for the hydrolysis ofprotein and nucleic acid reserves are present in the germinatingcotyledon. The fate of hydrolytic products was determined byinjecting leucine-14C or adenine-8-14C into the cotyledons.At most, 20 per cent of the leucine-14C and 10 per cent of theadenine-8-14C administered were transported from the cotyledonto axis tissues. Both compounds were extensively metabolizedand the labelling patterns suggest that different metabolicpathways are in operation in the two organs. The amounts ofadenine incorporated into nucleic acids and of leucine incorporatedinto protein in the cotyledons suggest that synthesis and turnoverwere occurring at a rapid rate. The adenine transported fromthe cotyledon was not readily available for nucleic acid synthesisin the axis whereas transported leucine was readily incorporatedinto axis protein. 相似文献
18.
LOZANO JOSE L.; WETTLAUFER SCOTT H.; LEOPOLD A. CARL 《Journal of experimental botany》1989,40(12):1337-1340
As part of a search for biochemical indicators of seed withgood survival characteristics during storage, polyamine (PA)levels were measured in embryos for Zea mays seeds. PA levelswere determined in individual embryos of Mean Generation Analysis(MGA) of crosses between lines which show good (C2) and poor(C6) storage characteristics. A correlation was found betweenhigher PA contents (putrescine and spermidine) and superiorsurvival characteristics within the populations that were analysedby MGA. Titres of putrescine (PUT) and spermidine (SPD) showedthat three-quarters of the F2 resembled the C2 parent and aquarter resembled the C6 parent. Furthermore, the backcrossC6F1 showed that half of the embryos had PUT levels above theparental C6 line. A maternal inheritance effect was not observed.Neither spermine nor cadaverine content was correlated withthe survival inheritance pattern. Given the survival kineticsobtained, it is suggested that both the PA titres and the seedsurvival characteristics are determined by nuclear dominantfactors. Key words: Polyamines, Zea mays, seeds 相似文献
19.
Somatic Embryogenesis and Plant Regeneration from Cultured Leaf Explants of Zea mays 总被引:4,自引:0,他引:4
Young leaf segments of Zea mays L. seedlings were cultured onMurashige and Skoog's basal nutrient medium supplemented with2 mg l1 2, 4-D and sub-cultured on medium containing8 mg l1 2,4-D. Two types of callus tissues appearedembryogenicand non-embryogenic. The embryogenic callus tissue producednumerous somatic embryos which on transfer to media containinglow amounts of 2,4-D or ABA produced plantlets. Callus tissuesexhibited embryogenic potential for more than 1 year. Zea mays L. cv. Ageti-76, Zea mays L. cv. N-L-D-Comp., maize, leaf, callus, somatic embryogenesis, regeneration 相似文献
20.
Effect of Inorganic Phosphate on the Biosynthesis of Purine and Pyrimidine Nucleotides in Suspension-Cultured Cells of Catharanthus roseus 总被引:1,自引:0,他引:1
The levels of purine and pyrimidine nucleotides in suspensioncultures of Catharanthus roseus were determined 24 h after stationary-phasecells were transferred to fresh complete (+Pi)or phosphate-deficient (Pi) Murashige-Skoogmedium. The levels of ATP, GTP, UTP and CTP were from approx.3 to 5-fold greater in the cells grown in +Pimedium than in the cells grown in Pi medium.The levels of almost all other nucleotides were slightly higherin the cells in +Pi medium. The rates of de novoand salvage biosynthesis of purine and pyrimidine nucleotideswere estimated from the rates of incorporation of radioactivityfrom [14C]formate, [214C]glycine, NaH14CO3, [614C]orotate,[814C]adenine, [814C]adenosine, [214C]uraciland [214C]uridine. The results indicated that the activityof both the de novo and the salvage pathway was higher in thecells in +Pi medium than in the cells in Pimedium. The rate of degradation estimated from the rate of releaseof 14CO2 from labelled purines and pyrimidines indicated thatdegradation of uridine was significantly reduced in the cellsin +Pi medium, but no significant difference wasfound in the degradation of adenine, adenosine and uracil. Thepossible role of Pi in the control of the biosynthesis of nucleotidesand in the degradation of uridine is discussed. Catharanthus roseus, Madagascar periwinkle, suspension culture, inorganic phosphate, nucleotides, purines, pyrimidines, biosynthesis, degradation 相似文献