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1.
O-Benzylhydroxylamine (OBHA) is a potent inhibitor of phenylalanineammonialyase (PAL, EC 4.3.1.5
[EC]
) and phenylpropanoid metabolismas evidenced by its effects on three plant species [soybean(Glycine max (L.) Merr.), buckwheat (Fagopyrum esculentum Moench.),and mung bean (Vigna radiata L.)]. When supplied to roots, OBHA(105 M) did not significantly inhibit light- or dark-growthof soybean seedlings, but reduced (25%) soluble hydroxyphenoliccompound accumulation in light-grown axes. Higher concentrations(5105 M) of OBHA caused reductions (25%) in axis freshweight of light-grown seedlings (72 h), but did not lower axisweight of dark-grown seedlings. Anthocyanin accumulation inhypocotyls of intact mung bean seedlings was reduced by 25%after 3 days light growth after treatment with OBHA (105M) via root feeding. Anthocyanin content of excised, etiolatedbuckwheat hypocotyls floated on solutions of OBHA (105M) and incubated in the light for 24 h was reduced by 40%. L-Phenylalanineand t-cinnamic acid, intermediates of phenylpropanoid metabolism,were able to partially reverse this inhibition in buckwheat.Extractable PAL activity (specific activity basis) in soybeanaxes was substantially reduced (20% in dark, 40% in light) asearly as 24 h after root feeding with OBHA (105 M). Reductionof PAL activity (specific activity or per axis basis) by OBHAcompared to control levels, continued throughout a time courseof 96 h. Kinetic studies on soybean PAL revealed a Km of 1.1mM for L-phenylalanine and an apparent Ki of 3.5 µM forOBHA. (Received May 31, 1985; Accepted August 6, 1985) 相似文献
2.
Field experiments using two soybean (Glycine max L. Merrill)cultivars (Elgin 87 and Essex) wereconducted for 2 years near Lexington, KY, USA to evaluate theeffect of source-sink alterations on seed carbohydrate statusand growth. Sucrose concentrations in developing cotyledonsof control plants were consistently low (<50 m M) early inseed development, but they increased to 100150 m M byphysiological maturity. The concentrations increased in bothyears by 47 to 59% when 90% of the pods were removed from Elgin87, but the increase had no effect on individual seedgrowth rate (SGR). Shading (80%) reduced cotyledon sucrose levelsand SGR in both years. The critical cotyledon sucrose concentration(the concentration providing 80% of the maximum cotyledon growthrate) was estimated fromin vitro cotyledon growth at sucroseconcentrations of 0200 m M. These critical concentrationsvaried from 72124 m M;in planta control cotyledon sucroseconcentrations were below this critical level during the firsthalf of seed growth but exceeded it in the later stages of growthin all experiments. The estimated critical concentration wasconsistent with the failure of in planta SGR to respond to anincrease in assimilate supply and with the reduction in SGRassociated with a decrease in assimilate supply. The resultssuggest that soybean SGR is generally sink limited if photosynthesisincreases during seed filling, but source limited if photosynthesisis reduced. Copyright 2001 Annals of Botany Company Glycine max(L.) Merrill, soybean, source-sink ratios, sucrose, starch, depodding, shade, in vitro culture 相似文献
3.
An extract from the roots of Lotus pedunculatus plants was foundto contain a compound toxic towards fast-growing Lotus rhizobia.This compound was identified as a flavolan, which has a prodeiphinidin:procyanidin ratio of 75:25. A fast-growing strain of Rhizobium(NZP2213) which forms ineffective root nodules on L. pedunculatuswas four times more sensitive to this flavolan (ED50 = 25 ?gml1) than another strain (NZP2037, ED50 = 100 ?g ml1)which forms effective root nodules on this species. The rootsof another Lotus species, L. tenuis, on which both strains ofRhizobium form effective root nodules, also contained a flavolan( 95% procyanidin) but both strains were relatively insensitiveto this flavolan (EDED50 = 350 to 500 ?g ml1) L. pedunculatusplants bearing ineffective root nodules contained two to threetimes more flavolan in their roots (57 mg g1 fr.wt.)than uninoculated control plants. Experiments with seven otherLotus species and with hybrid plants developed between L. pedunculatusand L. tenuis showed a relationship between the prodeiphinidin:procyanidin ratio of the flavolan in their roots and the effectivenessof root nodules formed on these plants by NZP2213. Quantitativebinding studies of the flavolan from L. pedunculatus to NZP2037and NZP2213 indicated that, while the affinity constants forbinding were similar for both strains, the surface of strainNZP2037 contained four times more binding sites than NZP2213,possibly correlating with this strain's ability to toleratehigher concentrations of this flavolan. It is suggested thatthe differential sensitivity of these two strains of Rhizobiumto flavolans is related to their ability to form effective rootnodules on Lotus species. 相似文献
4.
Plant Growth-promoting Rhizobacteria and Soybean [ Glycine max (L.) Merr.] Growth and Physiology at Suboptimal Root Zone Temperatures 总被引:1,自引:0,他引:1
Application of plant growth-promoting rhizobacteria (PGPR) hasbeen shown to increase legume growth and development under optimaltemperature conditions, and specifically to increase nodulationand nitrogen fixation of soybean [Glycine max (L.) Merr.] overa range of root zone temperatures (RZTs). Nine rhizobacteriaapplied into soybean rooting media were tested for their abilityto reduce the negative effects of low RZT on soybean growthand development by improving the physiological status of theplant. Three RZTs were tested: 25, 17.5, and 15 °C. At eachtemperature some PGPR strains increased plant growth and development,but the stimulatory strains varied with temperature. The strainsthat were most stimulatory at each temperatures were as follows:15 °CSerratia proteamaculans 1102; 17.5 °CAeromonashydrophila P73, and 25 °CSerratia liquefaciens 268.Because enhancement of plant physiological activities were detectedbefore the onset of nitrogen fixation, these stimulatory effectscan be attributed to direct stimulation of the plant by thePGPR rather than stimulation of plant growth via improvementof the nitrogen fixation symbiosis. Legume; nitrogen fixation; nodulation; root zone temperature; PGPR 相似文献
5.
Overcoming Incompatibility in Brassica campestris L. by Carbon Dioxide, and Dark Fixation of the Gas by Self- and Cross-pollinated Pistils 总被引:1,自引:0,他引:1
Supplementing pollen suspension cultures with CO2 (35per cent) caused a marked increase in germination and tube growthin vitro in Brassica campestris L. cv. toria. A weakening ofself-incompatibility by increased CO2 levels from 35per cent was observed. The percentage of pollen tubes whichpenetrated the cuticle layer of stigmatic papilla cells in self-pollinatedpistils was high when CO2 level was 5 per cent. Phosphoenolpyruvate (PEP) carboxylase activity was greater in the pollengerminated in 4 per cent CO2 as compared to air (0.03 per cent).A possible role of CO2 for self-recognition and control of pollentube growth is proposed, proposed. Brassica campestris L., carbon dioxide, self-incompatibility, phosphoenol pyruvate carboxylase 相似文献
6.
Ward, D. A. and Drake, B. G. 1987. Photoinhibition under atmosphericO2, the activation state of RuBP carboxylase and the contentof photosynthetic intermediates in soybean and wheat.J.exp. Bot. 38: 19371948. Associations between photosynthesis, the activation state ofRuBP carboxylase and the contents of photosynthetic intermediateswere compared in soybean and wheat leaves before and after exposureto photoinhibitory treatments in the presence of atmosphericO2. Exposing attached leaves to a supra-saturating irradiance(3 800 µmol quanta m 2 s1) for 2 h in CO2-freeair decreased carboxylation efficiency and the light-saturatedphotosynthetic rate in air by approximately 50%. Exposure tothe photoinhibitory treatment for periods in excess of 2 h didnot cause a further decrease of photosynthesis in soybean. Althoughphotosynthesis was reduced, the initial and total (fully-activated)activities of ribulose 1,5-bisphosphate carboxylase (RuBPCase)in leaf extracts were unaltered in each species by the photoinhibitorytreatment. This was true for leaves sampled under both air andat a rate-limiting intercellular CO2 partial pressure (Ci) of75 µPa Pa1. The contents of ribulose l,5-bisphosphate(RuBP) and 3-phosphoglyceric acid (3-PGA) were reduced by thephotoinhibitory treatment in soybean leaves sampled in air andat a rate-limiting Ci, although the RuBP/3-PGA ratio was unaffected.The relative reduction of RuBP content in soybean leaves atrate-limiting C1 was similar to the corresponding reductionof carboxylation efficiency. For wheat,the relative reductionof RuBP content at rate-limiting Ci (19%) caused by thephotoinhibitory treatment was considerably less than the correspondingdecrease of carboxylation efficiency (49%).The RuBP/3-PGAratio of wheat was also increased significantly by the photoinhibitorytreatment The significance of these observations to the regulationof CO2-limited photosynthesis in leaves experiencing photoinhibitionunder atmospheric oxygen is discussed. Consideration is alsogiven to the previous contention that contemporary measurementsof initial activity in crude extracts may provide a spuriousindication of the amount of the enzyme-CO2-Mg2 + form of RuBPcarboxylase present in the leaf. Key words: Carboxylation efficiency, RuBP carboxylase, photoinhibition, RuBP, 3-PGA 相似文献
7.
Significant amounts of ethylene was produced by Pseudomonassolanacearum (all strains), P. syringae pv. phaseolicola (Kudzustrains isolated from Pueraria lobata) and Erwinia rhapontici(2 strains out of 22) out of 24 species, 3 subspecies and 38pathovars of plant pathogenic bacteria tested in yeast extract-peptonebroth. The bean strains of P. syringae pv. phaseolicola causinghalo blight in kindney bean plants did not produce ethylene.The Kudzu strains produced ethylene at a rate of 7 to 100?109nl cell1 h1, which was 500 to 1,000 times higherthan that of P. solanacearum and several times higher than thatof Penicillium digitatum, the most potent ethylene producerknown among microorganisms. The presence of living cells was essential for ethylene productionby the Kudzu strains. The bacterium effectively produced ethylenefrom amino acids such as glutamate, aspartate and their amides.Although glucose and succinate were also good substrates forethylene biosynthesis, the rate of ethylene production was significantlysmaller than that with glutamate. Methionine, which is knownas the precursor of ethylene in plants, had no effect on ethyleneproduction by the bacterium. 1-Aminocyclopropane-1-carboxylicacid (ACC) also had no effect on ethylene production, and therewas not enough ACC in the bacterial cells to account for thehigh rate of ethylene production. Ethylene production from glutamatewas inhibited by n-propylgallate and EDTA, but not by aminoethoxyvinylglycine.These results indicate that ACC is not involved as an intermediatein the process of ethylene biosynthesis by the bacterium, suggestingthe presence of a pathway different from that of plant tissues. (Received September 4, 1984; Accepted October 27, 1984) 相似文献
8.
Ruchti, M. and Widmer, F. 1986. Isocitrate lyase from germinatingsoybean cotyledons: purification and characterization.J.exp. Bot. 37: 16851690. Isocitrate lyase (E.C. 4.1.3.1
[EC]
) was purified from the cotyledonsof 7-d-old soybean seedlings. Three molecular forms were detectedwith pi values of 6·46, 6·25 and 6·0. Themain form (pl = 6·46) had an approximate Mr of 130000,a pH optimum of 8·0, a Km (isocitrate) close to 2·0mol m3 and a molecular activity of 615 min 1 at25 °C. The purified enzyme is not a glycoprotein and isheat labile. Key words: Isocitrate lyase, soybean 相似文献
9.
Rhoden KJ Cianchetta S Stivani V Portulano C Galietta LJ Romeo G 《American journal of physiology. Cell physiology》2007,292(2):C814-C823
The sodium iodide symporter (NIS) mediates iodide (I) transport in the thyroid gland and other tissues and is of increasing importance as a therapeutic target and nuclear imaging reporter. NIS activity in vitro is currently measured with radiotracers and electrophysiological techniques. We report on the development of a novel live cell imaging assay of NIS activity using the I-sensitive and genetically encodable yellow fluorescent protein (YFP) variant YFP-H148Q/I152L. In FRTL-5 thyrocytes stably expressing YFP-H148Q/I152L, I induced a rapid and reversible decrease in cellular fluorescence characterized by 1) high affinity for extracellular I (35 µM), 2) inhibition by the NIS inhibitor perchlorate, 3) extracellular Na+ dependence, and 4) TSH dependence, suggesting that fluorescence changes are due to I influx via NIS. Individual cells within a population of FRTL-5 cells exhibited a 3.5-fold variation in the rate of NIS-mediated I influx, illustrating the utility of YFP-H148Q/I152L to detect cell-to-cell difference in NIS activity. I also caused a perchlorate-sensitive decrease in YFP-H148Q/I152L fluorescence in COS-7 cells expressing NIS but not in cells lacking NIS. These results demonstrate that YFP-H148Q/I152L is a sensitive biosensor of NIS-mediated I uptake in thyroid cells and in nonthyroidal cells following gene transfer and suggest that fluorescence detection of cellular I may be a useful tool by which to study the pathophysiology and pharmacology of NIS. thyroid; fluorescence microscopy; FRTL-5 cells 相似文献
10.
Sink-limited conditions, defined as treatment with continuousillumination, cause a reduction in the rate of photosyntheticfixation of CO2 in single-rooted leaves of soybean (Glycinemax. Merr. cv. Turunoko). We suggested previously that thisreduction is due to a deactivation of ribulose-1,5-bisphosphatecarboxylase (RuBPcase, E.C. 4.1.1.39
[EC]
) that is caused by a decreasein the level of Pi in the leaves [Sawada et al. (1989) PlantCell Physiol. 30: 691, Sawada et al. (1990) Plant Cell Physiol.31: 697]. In the present study, the mechanism of regulationof RuBPcase activity by Pi was examined. The activity of RuBPcasein the sink-limited leaves, exposed for 6 or 7 d to continuousillumination to alter the source/sink balance, was enhancedwith increasing concentrations of Pi, in a CO2-free preincubationmedium in the presence of 5 mM MgCl2 The maximum value [6.3µmole CO2 (mg Chl)1 min1] was obtained atapproximately 5 mM Pi after a 5 min incubation, being 3 timesof the activity without the preincubation. The activity of acrude preparation of RuBPcase that had been deactivated by removalof CO2 and Mg2+ ions by the gel filtration was 5.29.3nmole CO2 (mg protein)1 min1 and was also enhancedby Pi plus Mg2+ ions. The maximum value [147151 nmoleCO2 (mg protein)1 min1] was attained at 5 mM Piafter a 5 min incubation. The cycle of activation and inactivationof deactivated crude RuBPcase was perfectly reversible by additionof Pi to the enzyme and removal of Pi from the enzyme. Levelsof free Pi and of esterified phosphate in the sink-limited leaveswere 69% and 31% of the total phosphate, respectively. By contrast,in the control leaves, these values were 87% and 13%, respectively.These results support our previously stated hypothesis and indicatean important role for free Pi in the regulation of RuBPcaseactivity, in particular in sink-limited plants. (Received February 21, 1992; Accepted July 23, 1992) 相似文献
11.
Dimethipin (2,3-Dihydro-5,6-dimethyl-1,4-dithiin 1,1,4,4-tetraoxide) Effects on Soybean Seedling Growth and Metabolism 总被引:1,自引:0,他引:1
Three-day-old dark-grown soybean [Glycine max (L.) Merr.] seedlingswere transferred to 2 mM CaSO4 or 105 M dimethipin in2 nM CaSO4 and root-fed via liquid culture. Plants were placedin continuous darkness or in continuous white light (200 µE.m2?s11,PAR) at 25?C. Dimethipin inhibited root and shoot elongationin dark-grown plants after 24 h and 48 h, respectively. In thelight, root elongation was inhibited also after 24 h, but hypocotylelongation was not significantly affected. Extractable phenylalanineammonia-lyase (PAL) activity per axis in dimethipin-treateddark-grown axes was not generally affected but, in the lightdimethipin caused a significant decrease in PAL activity (24to 96 h). Total soluble hydroxyphenolics in axes were not affectedby dimethipin in light- or dark-grown plants. Anthocyanin andchlorophyll levels were lowered in hypocotyls of dimethipin-treatedplants after 48 to 96 h. Soluble protein in hypocotyls of light-or dark-grown seedlings was not substantially affected by dimethipin.Nitrate reductase (NR) activity (per organ) was generally notaffected by dimethipin in light-grown cotyledons, but in theroots of these seedlings, NR activity was significantly decreased.Proteolytic enzyme activity using three substrates (leucine-p-nitroanilide,LPNA; proline-p-nitroanilide, PPNA; and benzoylarginine-p-nitroanilide,BAPA) indicated little effect on enzyme activities per organin roots and hypocotyls. These data suggest that dimethipinat low concentrations can cause significant growth inhibitionin soybean seedlings grown in either light or darkness and thatfurthermore, extractable activities of some enzymes associatedwith nitrogen metabolism and secondary metabolism are alteredby this chemical. Light also plays a role in the activity ofthis chemical. (Received November 29, 1983; Accepted January 25, 1984) 相似文献
12.
A Far-Upstream Sequence of the Wheat Histone H3 Promoter Functions Differently in Rice and Tobacco Cultured Cells 总被引:2,自引:0,他引:2
Ito Takuya; Fujimoto Yoshinobu; Nakayama Takuya; Iwabuchi Masaki 《Plant & cell physiology》1995,36(7):1281-1290
The cis-regulatory function of a far-upstream sequence (1,711to 186) of the promoter of the wheat gene for histoneH3 (TH012) was analyzed in cultured rice and tobacco cells ina transient expression system with the gene for rß-D-glucuronidaseas a reporter gene. The far-upstream sequence was necessaryfor full activity of the H3 promoter in rice cells but did notenhance the activity of the proximal promoter in tobacco cells.Dissection analysis of the far-upstream sequence revealed theexistence of several positive and negative cis-acting sequencesin this region, some of which functioned differently in riceand tobacco cells. In gain-of-function experiments with ricecells, the sequence from 848 to 704, containingthe CCAAT and octamer (CaCGGATC) motifs, functioned in an orientation-independentmanner, whereas the sequence from 703 to 486 functionedin an orientation-dependent manner. By contrast, both sequencesexhibited an orientation-dependent cis-function in tobacco cells.These findings suggest that some cis-regulatory sequences inthe far-upstream region of the H3 promoter function differentlyin rice and tobacco cells. (Received May 10, 1995; Accepted August 8, 1995) 相似文献
13.
Fine Structure of Peanut Root Nodules Induced by Nod+Fix- Strains of Bradyrhizobium with Special Reference to Lipid Bodies 总被引:1,自引:0,他引:1
Ineffective nodules of peanut induced by two nod+fixstrains of Bradyrhizobium sp. were compared with the ones inducedby nod+fix+ strain NC92. One of the fix strains, 639is a transconjugate Tn5 mutant of NC92, while the other, 7091,is an isolate from ICRISAT soil. Both induce small nodules lackingleghemoglobin and nitrogen-fixing activity. Ultrastructuralobservations revealed that the nodules of 639, have enlargedperibacteroid space and lack persistence of nodule function.The 7091-induced nodules showed impediment in bacteroid releaseand differentiation. In both the ineffective nodules large amountsof lipid bodies were found to accumulate several times in excess,compared to the effective NC92 nodules. The large lipid accumulationin absence of nitrogen fixation supports the hypothesis thatin peanut nodules lipid bodies are utilized as a supplementarysource of carbon and energy for nitrogen fixation. Peanut, lipid bodies, nitrogen fixation, nod+fix Bradyrhizobium, ultrastructure 相似文献
14.
In Saccharomyces cerevisiae, protoplasts from respiratory-deficient(rho) cytoplasmic mutant cells were transformed intorespiratory-sufficient (rho+) cells by incubation with mitochondriaprepared from rho+ cells in the presence of polyethylene glycoland CaCl2. Mitochondria prepared from different species, Hansenulawingei and Schizosaccharomyces pombe, also caused the transformationof S. cerevisiae rho protoplasts into the rho+ cellsas previously reported (14) The obtained transformants wereconfirmed to contain one nucleus and several mitochondrial DNAsby fluorescent staining of DNA. The transformants clearly restoredcytochromes a and b while untransformed recipient cells lackedthe cytochromes. In order to know the mechanism of the transformation,physiological measurement of endocytotic activity of protoplastsand cytological examination of mitochondria-protoplast aggregatesunder the transforming condition were performed. Protoplastshad significant endocytotic activity under this condition. Onthe other hand, fluorescence and electron microscopic observationsindicated that mitochondria forming aggregates with protoplastswere subsequently integrated into recipient protoplasts throughfusion rather than endocytosis. However, the possibility ofendocytosis could not be completely excluded when the low frequencyof the transformation (about 106 to 107) was takeninto account. This is discussed in this paper. A new convenientmethod for measuring endocytosis is also presented. (Received September 27, 1979; ) 相似文献
15.
Effects of Growth Regulators on Polyamine Content and Peroxidase Activity in Hevea brasiliensis Callus 总被引:2,自引:0,他引:2
3, 4-dichlorophenoxyacetic acid (3,4-D) and benzylaminopurine(BAP) at 9 µM (control medium) was compared with 4.5,2.25, and 0.45 µM for ability to induce callogenesis andembryogenesis from seed explants of Hevea brasiliensis. Supplyingthese growth regulators at 4.5 µM for 20 d improved embryogenicpotential compared with the control medium (El Hadrami, Carronand d'Auzac, 1991, Annals of Botany 67, 511515), sustainedputrescine, spermidine and spermine at a higher level throughoutof much of the culture period (4070 d), and maintainedlow levels of peroxidase activity. In the control medium, poorcallus embryogenesis is considered a consequence of rapid ageingof tissues characterized by (i) acceleration of an early buttransient production of polyamines, which promoted embryogeniccapacity, and (ii) an early peak in peroxidase activity thatwas positively correlated with callus browning, one of the factorslimiting embryogenesis. Somatic embryogenesis, polyamines, peroxidase, Hevea brasiliensis, rubber-tree 相似文献
16.
Light, temperature and nitrogen as interacting factors affecting diel vertical migrations of dinoflagellates in culture 总被引:11,自引:0,他引:11
Diel vertical migrations of the marine dinoflagellates Gonyaulaxpolyedra Stein and Ceratium furca (Ehr.) Clap, et Lachm. werefollowed in a laboratory tube (2.02 m x 0.25 m) under a 12:12hlight:dark cycle. The effects of temperature stratification,two levels of surface irradiance and nitrogen depletion on patternsof vertical migrations were examined. At temperatures between2226°C with small temperature gradients, both speciesmigrated at a rate of 0.7 1.0 m h1. Steeper thermoclines(ca. 0.8°C 0.1 m1) with temperatures below ca. 20°Ccaused a marked decrease in swimming speed which resulted inaccumulations of cells in these thermocline regions. Under conditionsof nutrient sufficiency both algae migrated into the surfacelayers at irradiance values of over 1000 µE m2s1. Increasing nitrogen depletion caused the downwardmigration of both algae to commence progressively earlier inthe day and before the end of the light period. The earlierdownward migrations enabled a more complete descent throughthe thermocline. Nitrogen depleted cells of Gonyaulax continuedto undertake vertical migrations but avoided high irradiancesthus forming subsurface maxima at irradiance levels close to150 µE m2 s1. Ceratium cells which exhaustedboth inorganic nitrogen and phosphorus ceased to migrate accompaniedby a large change in cellular fluorescence. 相似文献
17.
Malondialdehyde, a product of lipid oxidation, increased graduallywhen Euglena gracilis cells were bubbled with 240 µ1.liter1ozone (delivery rate of 1µmolO3.min1) for 120 min.Simultaneously, the sulfhydryl group content decreased by 36%during the treatment, which was mainly due to oxidation of proteinsulfhydryl groups. The molar amount of SH groups oxidized was3 times higher than that of fatty acid oxidized, indicatingthat sulfhydryl groups were more accessible or more easily oxidizedby O3 than fatty acids. When Euglena cells were allowed to recoverunder autotrophic growth conditions following O3 treatment,viable cells were incapable of dividing during the first 5 hof the recovery period but regenerated SH groups nearly to thecontrol level. The increase of SH content during this periodpreceded the resumption of cell division and the restorationof normal growth. These results suggest that the regenerationof SH groups by Euglena cells is a part of a mechanism involvedin the repair of oxidative damage caused by ozone and is anessential step for the initiation of cell division. (Received July 20, 1987; Accepted December 14, 1987) 相似文献
18.
Lepic E Burger D Lu X Song W Feng Q 《American journal of physiology. Cell physiology》2006,291(6):C1240-C1246
We recently demonstrated that deficiency in endothelial nitric oxide synthase (eNOS) results in congenital septal defects and postnatal heart failure. The aim of this study was to investigate the role of eNOS in cardiomyocyte proliferation and maturation during postnatal development. Cultured eNOS knockout (eNOS/) cardiomyocytes displayed fewer cells and lower bromodeoxyuridine (BrdU) incorporation in vitro compared with wild-type (WT) cardiomyocytes (P < 0.05). Treatment with the nitric oxide (NO) donor diethylenetriamine NONOate increased BrdU incorporation and cell counts in eNOS/ cardiomyocytes (P < 0.05). Inhibition of nitric oxide synthase activity using NG-nitro-L-arginine methyl ester decreased the level of BrdU incorporation and cell counts in WT cardiomyocytes (P < 0.05). Vascular endothelial growth factor (VEGF) increased the level of BrdU incorporation in cultured WT cardiomyocytes in a dose- and time-dependent manner (P < 0.05). Conversely, VEGF did not alter BrdU incorporation in eNOS/ cardiomyocytes (P = not significant). Furthermore, deficiency in eNOS significantly decreased BrdU labeling indexes in neonatal hearts in vivo. Although WT hearts displayed a rapid decrease in atrial natriuretic peptide (ANP) expression in the first week of neonatal life, ANP expression in eNOS/ hearts remain elevated. Our study demonstrated that NO production from eNOS is necessary for postnatal cardiomyocyte proliferation and maturation, suggesting that eNOS plays an important role during postnatal heart development. proliferation; heart development 相似文献
19.
Sawada Shinichi; Usuda Hideaki; Hasegawa Yasuhide; Tsukui Takahiro 《Plant & cell physiology》1990,31(5):697-704
The results of our previous study [Sawada et al. (1989) PlantCell Physiol. 30: 691] implied that, under sink-limited conditions,a decrease in the activity of ribulose-l,5-bisphosphate carboxylase(EC 4.1.1.39
[EC]
) caused a reduction in the rate of photosyntheticfixation of CO2 in single-rooted leaves of soybean (Glycinemax L. Merr. cv. Tsurunoko). This reduction in the rate of photosynthesisin source leaves seemed to correspond to a decrease in the demandby sink tissues for photoassimilates. In the present study,the activity of RuBPcase in vivo was estimated by measuringthe "initial" activity immediately after extraction from standardleaves (grown under a regime of 10 h of light and 14 h of darkness)and from sink-limited leaves (exposed for 6 or 7 d to continuouslight to alter the source/sink balance). The rate of photosynthesisin the sink-limited leaves decreased to 47% of that in the standardleaves. The "initial" activity of RuBPcase was 4.3 in the standardleaves but only 1.6 µmole CO2.(mg Chl)1.min1in the sink-limited leaves. These results appear to indicatethat the reduction in photosynthetic activity under sink-limitedconditions was mostly due to a deactivation of RuBPcase. Theactivity of deactivated RuBPcase in the sink-limited leaveswas restored to 4.1 µmole CO2.(mg Chl)1.min1by incubation of the enzyme in a medium that contained onlyNa2HPO4. This result suggests that free Pi in chloro-plastsplays an important role in the activation of the enzyme. Thelevel of Pi in the sink-limited leaves was 62% of that in thestandard leaves. On the basis of these various results, it appearsthat the deactivation of RuBPcase in the sink-limited leavesis the result of a decrease in the level of Pi. The role offree Pi in the activation of RuBPcase, in particular at atmosphericconcentrations of CO2, was also investigated. (Received November 30, 1989; Accepted May 11, 1990) 相似文献
20.
Imsande, J. 1986. Inhibition of nodule development in soybeanby nitrate or reduced nitrogen.J. exp. Bot. 37: 348355. Nodulation of hydroponically grown soybean plants [Glycine max(L.) Merr.] is inhibited by continuous growth in the presenceof 4· mol m3 KNO3 The presence of 4·0 molm3 starter nitrate for 3-6 d during noduledevelopment, however, subsequently stimulates nodule dry weightaccumulation and nitrogenase activity. These stimulations occureven though 4· mol m3 nitrate temporarily delaysnodule development, i.e. the late steps of nodule developmentare reversibly inhibited by a short-term exposure to 4·0mol m3 nitrate. On the other hand, treatment with 4·0mol m3 nitrate in excess of 14 d significantly reducesnodule dry weight Thus, extended growth in the presence of 4·0mol m3 KNO3 seems to block both early and late stepsof nodule development. Nodulation of hydroponically grown soybeansis also inhibited by continuous growth in the presence of 2·0mol m3 (NH4)2SO4 This inhibition is not caused by acidityof the growth medium. On the other hand, nodule development6 d after inoculation with Rhizoblum japonicum is not delayedby a 7-d exposure to 2·0 mol m3 (NH4)2SO4 butis partially inhibited by a prolonged exposure to (NH4)2SO4Because repression of nodulation by 4·0 mol m3KNO3 is more severe than that by 2·0 mol m3 (NH4)2SO4and because ammonium taken up by the soybean plant is not activelyoxidized to nitrate, it is suggested that there are at leasttwo mechanisms by which nitrate utilization represses noduleformation in soybean. Key words: Glycine max, nitrogen, nitrogen fixation, nodulation 相似文献