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1.
Summary This communication reports the photoautotrophic growth of hormone and vitamin independent cell suspension cultures of Chenopodium rubrum. The transfer of cells from stationary growth into fresh culture medium results in a high protein formation, followed by an exponential phase of cell division, whereas the onset of rapid chlorophyll formation is delayed for 4 days. At the stage of most rapid cell division there is no net synthesis of starch and sugar. When the cells enter stationary growth, there is a progressive accumulation of chlorophyll, sugar, and starch.Photoautotrophic cell cultures assimilate about 80–90 mol CO 2/mg chlorophyll X hour. Dark CO 2 fixation is about 3.7% to 2.2% of the light values during exponential and stationary growth, respectively. As shown by short-term 14CO 2 fixation, CO 2 is predominantly assimilated through ribulosebisphosphate carboxylase via the Calvin pathway. There is a significant increase in the 14C label of C 4 carboxylic acids in exponentially dividing cells as compared to cells from stationary growth. The in vitro activity of phosphoenolpyruvate carboxylase and ribulosebisphosphate carboxylase is almost equal during exponential cell division. A decrease in cell division activity is accompanied by a significant change in the specific activities of both carboxylation enzymes. In non dividing cells from stationary growth the activity of ribulosebisphosphate carboxylase is greately enhanced and that of phosphoenolpyruvate carboxylase is reduced, documenting the development of carboxylation capacities typical for C 3-plants.The experimental results provide evidence that phosphoenolpyruvate carboxylase activity might be regulated by ammonia and could be involved in anaplerotic CO 2 fixation which supplies carbon skeletons of the citric acid cycle.Abbreviations 2,4-D
2,4-dichlorophenoxyacetic acid
- EDTA
ethylene-diamine-tetraacetic acid
- FDP
fructose bisphosphate
- F-6-P
fructose-6-phosphate
- G-6-P
glucose-6-phosphate
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- PGA
3-phosphoglyceric acid
- PEP
phosphoenolpyruvate
- RuDP
ribulosebisphosphate 相似文献
2.
The carboxylation of ribulose-1,5-diphosphate was demonstrated in vitro with extracts of ctiolated seedling roots. The presence of ribulose-1,5-diphosphate carboxylase was characterized in the subcellular fraction enriched in amyloplasts. Synthesis of chlorophyll, development of CO 2 fixation capacities and of Hill activity upon illumination have been studied with roots of Lens culinaris seedlings. The marked increases in CO 2 fixation with ribulose-1,5-diphosphate as the substrate and in Hill activity that occur after a lag phase seem to be related to cytological changes during the greening of roots. 相似文献
3.
Summary Cell suspension cultures of Chenopodium rubrum have been grown for more than 2 years photoautotrophically with CO 2 as sole carbon source. Average increase in fresh weight is appr. 600% within 14 days. The chlorophyll content of photoautotrophic cells (200 g/g fresh weight) is much higher than of photomixotrophic cells (50 g/g fresh weight). The photosynthetic activity of the cells (190 moles CO 2×mg –1 chlorophyllXh –1) is comparable to the values found with intact leaves. As shown by short-term 14CO 2 photosynthesis, both, the photomixotrophic and the photoautotrophic cell suspension cultures assimilate CO 2 predominantly via the Calvin pathway.Major differences were found with cells from either exponential or stationary phase of growth with regard to differential labelling of 3-phosphoglyceric acid, malate, sucrose and glucose/fructose. In vitro measurements of carboxylation reactions only partially corroborate our findings with 14CO 2 incorporation. The ratio of ribulosebisphosphate to phosphoenolpyruvate carboxylase activity is 4.7 for leaves of C. rubrum, 1.2 for photoautotrophic cells during stationary growth and 0.5 for cells during exponential growth phase, however, 0.18 was found for photomixotrophic cells. Though the 14CO 2 incorporation into 3-phosphoglyceric acid is clearly higher than into malate, the in vitro activity of phosphoenolpyruvatecarboxylase is 2–6 fold higher than that of ribulosebisphosphate carboxylase. We postulate that anaplerotic reactions of the tricarboxylic acid cycle are involved in the regulation of phosphoenolpyruvate carboxylase.Abbreviations 2,4-D
didilorophenoxyacetic acid
- EDTA
ethylene-diamine-tetraacetic acid
- fr. w.
fresh weight
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- PGA
3-phosphoglyceric acid
- PPO
2,5-diphenyloxazole
- PEP
phosphoenolpyruvate
- RuBP
nbulosebisphosphate 相似文献
4.
Kinetic properties of soybean net photosynthetic CO 2 fixation and of the carboxylase and oxygenase activities of purified soybean ( Glycine max [L.] Merr.) ribulose 1, 5-diphosphate carboxylase (EC 4.1.1.39) were examined as functions of temperature, CO 2 concentration, and O 2 concentration. With leaves, O 2 inhibition of net photosynthetic CO 2 fixation increased when the ambient leaf temperature was increased. The increased inhibition of CO 2 fixation at higher temperatures was caused by a reduced affinity of the leaf for CO 2 and an increased affinity of the leaf for O 2. With purified ribulose 1,5-diphosphate carboxylase, O 2 inhibition of CO 2 incorporation and the ratio of oxygenase activity to carboxylase activity increased with increased temperature. The increased O 2 sensitivity of the enzyme at higher temperature was caused by a reduced affinity of the enzyme for CO 2 and a slightly increased affinity of the enzyme for O 2. The similarity of the effect of temperature on the affinity of intact leaves and of ribulose 1,5-diphosphate carboxylase for CO 2 and O 2 provides further evidence that the carboxylase regulates the O 2 response of photosynthetic CO 2 fixation in soybean leaves. Based on results reported here and in the literature, a scheme outlining the stoichiometry between CO 2 and O 2 fixation in vivo is proposed. 相似文献
5.
A cell line of M. polymorpha was grown photoautotrophically in liquid suspension culture using 1% CO 2 in air as sole carbon source. The growth rate in terms of cell dry-weight during the exponential phase was 0.171 and the doubling time was 1.76 d. The rate of increase in chlorophyll was 1.6 times higher than the growth rate. The highest content of chlorophyll was 24 mg g -1 dry weight, and the photosynthetic activity of the cells in the exponential phase, as calculated from the growth rate, was at least 60 mol mg -1 chlorophyll h -1. 相似文献
6.
The nature and sequence of metabolic events during phase II (early morning) Crassulacean acid metabolism in Opuntia erinacea var columbiana (Griffiths) L. Benson were characterized. Gas exchange measurements under 2 and 21% O 2 revealed increased O 2 inhibition of CO 2 fixation with progression of phase II. Malate and titratable acidity patterns indicated continued synthesis of C 4 acids for at least 30 minutes into the light period. Potential activities of phosphoenolpyruvate carboxylase (PEPC) and NADP-malic enzyme exhibited little change during phase II, while light activation of NADP-malate dehydrogenase, pyruvate, orthophosphate dikinase, and ribulose-1,5-bisphosphate carboxylase was apparent. Short-term 14CO 2 fixation experiments showed that the per cent of 14C incorporated into C 4 acids decreased while incorporation into other metabolites increased with time. PEPC exhibited increased sensitivity to 2 millimolar malate, and the Ki(malate) for PEPC decreased markedly with time. Sensitivity of PEPC to malate inhibition was considerably greater at pH 7.5 than at 8.0. The results indicate that decarboxylation and synthesis of malate occur simultaneously during the early morning period, and that phase II acid metabolism is not limited by CO 2 diffusion through stomata. With progression of phase II, CO 2 fixation by PEPC decreases while fixation by ribulose-1,5-bisphosphate carboxylase increases. 相似文献
7.
Shoots of anaerobically germinated Echinochloa crus-galli var oryzicola are nonpigmented whether germinated in light or dark, and chlorophyll synthesis is minimal for the first 12 to 18 hours of greening after exposure to ambient conditions. When chlorophyll development is compared between greening anoxic and etiolated shoots, there is a 100-fold difference in chlorophyll levels at 8 hours, an 8-fold difference at 24 hours, but roughly equal amounts at 60 hours. The chlorophyll a/b ratio approaches 3 earlier in greening anoxic shoots than in greening etiolated shoots, relative to total chlorophyll. The long lag in chlorophyll synthesis can be shortened by giving dark-grown anoxic shoots a 24-hour midtreatment of air before light. Development of photosynthetic activity in etiolated shoots, determined by CO2 gas exchange, 14CO2 uptake, and activity of carboxylating enzymes closely parallels development of chlorophylls. However, development of photosynthetic capability in greening anoxic shoots does not parallel chlorophyll development; ability to fix carbon lags behind chlorophyll synthesis. A reason for this lag is the very low activity of RuBP carboxylase during the first 36 hours of greening in anoxic shoots. The activity of phosphoenolpyruvate carboxylase is also delayed, but its kinetics more closely match those of chlorophyll development. 相似文献
8.
Changes in various components of photosynthetic apparatus during the 4 d dark incubation at 25°C of detached control and ultraviolet-B
(UV-B) treated Vigna unguiculata L. leaves were examined. The photosynthetic apparatus was more degraded in younger control seedlings and for a longer time
UV-B treated seedlings than in the older or for a shorter time UV-B treated seedlings. This was shown by determining the losses
in chlorophyll (Chl) and protein contents, variable fluorescence yield, photosystem (PS) 2, PS1 and ribulose-1,5-bisphosphate
carboxylase (RuBPC) activities, and photosynthetic 14CO 2 fixation. In contrast, the Car/Chl ratio increased during the dark incubation due to less expressed degradation of Car. 相似文献
9.
The enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase displayed near-maximal activity in isolated, intact barley ( Hordeum vulgare L. cv. Pennrad) mesophyll protoplasts. The carboxylase deactivated 40 to 50% in situ when protoplasts were dark-incubated 20 minutes in air-equilibrated solutions. Enzyme activity was fully restored after 1 to 2 minutes of light. Addition of 5 millimolar NaHCO 3 to the incubation medium prevented dark-inactivation of the carboxylase. There was no permanent CO 2-dependent activation of the protoplast carboxylase either in light or dark. Activation of the carboxylase from ruptured protoplasts was not increased significantly by in vitro preincubation with CO 2 and Mg 2+. In contrast to the enzyme in protoplasts, the carboxylase in intact barley chloroplasts was not fully reactivated by light at atmospheric CO 2 levels. The lag phase in carbon assimilation was not lengthened by dark-adapting protoplasts to low CO 2 demonstrating that light-activation of the carboxylase was not involved in photosynthetic induction. Irradiance response curves for reactivation of the the carboxylase and for CO 2 fixation by isolated barley protoplasts were similar. The above results show that there was a fully reversible light-activation of the carboxylase in isolated barley protoplasts at physiologically significant CO 2 levels. 相似文献
10.
Benzylaminopurine (BA) caused an enhancement of chlorophyll and protein content and a reduced elongation of primary barley leaves. BA did not change the rhythmic pattern of 14CO 2 fixation and activities of RuBP carboxylase, RuBP oxygenase, glycolate oxidase and phosphoglycolate phosphatase, but the enzyme activities were enhanced and the level of 14CO 2 fixation was reduced. Light/dark 14CO 2 evolution ratio was affeoted by BA only in older leaves. BA acts sequentially on the activities of photosynthetic and photorespiratory enzymes. 相似文献
11.
Rate of photosynthesis and activities of photosynthetic carbon reduction cycle enzymes were determined in pods (siliqua),
whereas rate of dark CO 2 fixation, oil content and activities of enzymes involved in dark CO 2 metabolism were measured in seeds of Brassica campestris L. cv. Toria at different stages of pod/seed development. The period between 14 and 35 days after anthesis corresponded to
active phase of seed development during which period, seed dry weight and oil content increased sharply. Rate of pod photosynthesis
and activities of photosynthetic carbon reduction cycle enzymes were maximum in younger pods but sufficiently high levels
were retained up to 40 days after anthesis. The rate of dark 14CO 2 fixation in seeds increased up to 21 days after anthesis and declined thereafter but maintaining sufficiently high rates
till 35 days after anthesis. Similarly various enzymes viz., phosphoenolpyruvate carboxylase, NAD +-malate dehydrogenase and NADP +-malic enzyme, involved in dark CO 2 metabolism retained sufficient activities during the above period. These enzyme activities were more than adequate to maintain
the desired supply of malate which mainly arises from dark CO 2 fixation in seeds and further translocated to leucoplasts for onward synthesis of fatty acids. Enzyme localization experiments
revealed phosphoenolpyruvate carboxylase and enzymes of sucrose metabolism to be present only in cytosol, whereas enzymes
of glycolysis were present both in cytosolic and leucoplastic fractions. These results indicated that oil synthesis in developing Brassica seeds is supported by pod photosynthesis and dark CO 2 fixation in seeds as the former serves as the source of sucrose and the latter as a source of malate 相似文献
12.
A mass spectrometric method combining 16O/ 18O and 12C/ 13C isotopes was used to quantify the unidirectional fluxes of O 2 and CO 2 during a dark to light transition for guard cell protoplasts and mesophyll cell protoplasts of Commelina communis L. In darkness, O 2 uptake and CO 2 evolution were similar on a protein basis. Under light, guard cell protoplasts evolved O 2 (61 micromoles of O 2 per milligram of chlorophyll per hour) almost at the same rate as mesophyll cell protoplasts (73 micromoles of O 2 per milligram of chlorophyll per hour). However, carbon assimilation was totally different. In contrast with mesophyll cell protoplasts, guard cell protoplasts were able to fix CO 2 in darkness at a rate of 27 micromoles of CO 2 per milligram of chlorophyll per hour, which was increased by 50% in light. At the onset of light, a delay observed for guard cell protoplasts between O 2 evolution and CO 2 fixation and a time lag before the rate of saturation suggested a carbon metabolism based on phospho enolpyruvate carboxylase activity. Under light, CO 2 evolution by guard cell protoplasts was sharply decreased (37%), while O 2 uptake was slowly inhibited (14%). A control of mitochondrial activity by guard cell chloroplasts under light via redox equivalents and ATP transfer in the cytosol is discussed. From this study on protoplasts, we conclude that the energy produced at the chloroplast level under light is not totally used for CO 2 assimilation and may be dissipated for other purposes such as ion uptake. 相似文献
13.
Fruiting structures of a number of legumes including chickpea are known to carry out photosynthetic CO 2 assimilation, but the pathway of CO 2 fixation and particularly the role of phosphoenolpyruvate carboxylase (EC 4.1.1.31) in these tissues is not clear. Activities of some key enzymes of the Calvin cycle and C 4 metabolism, rates of 14CO 2 fixation in light and dark, and initial products of photosynthetic 14CO 2 fixation were determined in podwall and seedcoat (fruiting structures) and their subtending leaf in chickpea ( Cicer arietinum L.). Compared to activities of ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) and other Calvin cycle enzyme, viz. NADP +-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.13), NAD +-glyceraldehyde-3-phosphate dehydrogenase (EC 1.2.1.12) and ribulose-5-phosphate kinase (EC 2.7.1.19), the levels of phosphoenolpyruvate carboxylase and other enzymes of C 4 metabolism viz. NADP +-malate dehydrogenase (EC 1.1.1.82), NAD +-malate dehydrogenase (EC 1.1.1.37), NADP + malic enzyme (EC 1.1.1.40), NAD +-malic enzyme (EC 1.1.1.39), glutamate oxaloacetate transaminase (EC 2.6.1.1) and glutamate pyruvate transaminase (EC 2.6.1.2), were generally much higher in podwall and seedcoat than in the leaf. Podwall and seedcoat fixed 14CO 2 in light and dark at much higher rates than the leaf. Short-term assimilation of 14CO 2 by illuminated fruiting structures produced malate as the major labelled product with less labelling in 3-phosphoglycerate, whereas the leaf showed a major incorporation into 3-phosphoglycerate. It seems likely that the fruiting structures of chickpea utilize phosphoenolpyruvate carboxylase for recapturing the respired carbon dioxide. 相似文献
14.
The incorporation of 14CO 2 into glycolate by intact spinach leaf ( Spinacia oleracea L. var. Kyoho) chloroplasts exposed to 14CO 2 (NaH 14CO 3, 1 millimolar) in the light was determined as a function of O 2 concentrations in the reaction media. A hyperbolic saturation curve was obtained, apparent Km (O 2) of 0.28 millimolar, indicating that glycolate is produced predominantly by ribulose-1,5-bisphosphate carboxylase/oxygenase. A concentration gradient of glycolate was invariably observed between chloroplast stroma and the outside media surrounding chloroplasts during photosynthetic 14CO 2 fixation under an O 2 atmosphere. 相似文献
15.
A photoautotrophic soybean suspension culture (SB-P) was used to study CO 2 assimilation while exposed to elevated or ambient CO 2 levels. These studies showed that under elevated CO 2 (5% v/v) malate is the dominant fixation product, strongly suggesting that phosphoenolpyruvate carboxylase (PEPCase) is the primary enzyme involved in carbon fixation in these cells under their normal growth conditions. Citrate and [aspartate + glutamate] were also significant fixation products during fifteen minutes of exposure to 14CO 2. During the ten minute unlabeled CO 2 chase however, 14C-malate continued to increase while citrate and [aspartate + glutamate] declined. Fixation of 14CO 2 under ambient CO 2 levels (0.037%) showed a very different product pattern as 3-phosphoglycerate was very high in the first one to two minutes followed by increases in [serine + glycine] and [aspartate + glutamate]. Hexose phosphates were also quite high initially but then declined relatively rapidly. Thus, the carbon fixation pattern at ambient CO 2 levels resembles somewhat that seen in C3 leaf cells while that seen at elevated CO 2 levels more closely resembles that of a C 4 plant. The initial fixation product of C 3 plants, 3-PGA, was never detectable under high CO 2 conditions. These data suggest that an in vitro photoautotrophic system would be suitable for studying carbon fixation physiology during photosynthetic and non-photosynthetic growth.Abbreviations SB-P
photoautotrophic soybean cells
- PEPCase
phosphoenol-pyruvate carboxylase
- RuBPCase
ribulose bisphosphate carboxylase/oxygenase
- 3-PGA
3-phosphoglycerate 相似文献
16.
Dinoflagellates are important primary producers and major causative agents of harmful algal blooms in the global ocean. Despite the great ecological significance, the photosynthetic carbon acquisition by dinoflagellates is still poorly understood. The pathways of photosynthetic carbon assimilation in a marine dinoflagellate Prorocentrum donghaiense under both in situ and laboratory-simulated bloom conditions were investigated using a combination of metaproteomics, qPCR, stable carbon isotope and targeted metabolomics approaches. A rapid consumption of dissolved CO 2 to generate high biomass was observed as the bloom proceeded. The carbon assimilation genes and proteins including intracellular carbonic anhydrase 2, phosphoenolpyruvate carboxylase, phosphoenolpyruvate carboxykinase and RubisCO as well as their enzyme activities were all highly expressed at the low CO 2 level, indicating that C 4 photosynthetic pathway functioned in the blooming P. donghaiense cells. Furthermore, δ 13C values and content of C 4 compound (malate) significantly increased with the decreasing CO 2 concentration. The transition from C 3 to C 4 pathway minimizes the internal CO 2 leakage and guarantees efficient carbon fixation at the low CO 2 level. This study demonstrates the existence of C 4 photosynthetic pathway in a marine dinoflagellate and reveals its important complementary role to assist carbon assimilation for cell proliferation during the bloom period. 相似文献
17.
Suaeda fruticosa and S. monoica are important halophytes for ecological rehabilitation of saline lands. We report differential physio-chemical, photosynthetic, and chlorophyll fluorescence responses in these halophytes under 100 mM sodium chloride (NaCl), 50% strength (16.25 ppt) of seawater (SW)-imposed salinity, and 10% polyethylene glycol 6000 imposed osmotic stress at 380 (ambient) and 1200 (elevated) µmol mol–1 CO2 concentrations. SW salinity enhanced the growth in both species; however, compared with S. fruticosa, the S. monoica exhibited comparatively better growth and biomass accumulation under saline conditions at elevated CO2. Results demonstrated better photosynthetic performances of S. monoica under stress conditions at both levels of CO2, and this resulted in higher accumulation of carbon, nitrogen, sugar, and starch contents. S. monoica exhibited improved antenna size, electron transfer at PSII donor side, and efficient working of photosynthetic machinery at elevated CO2, which might be due to efficient upstream utilization of reducing power to fix the CO2. The δ13C results supported the operation of C4 CO2 fixation in S. monoica and C3 or intermediate pathway of CO2 fixation in S. fruticosa. Lower accumulation of reactive oxygen species, reduced membrane damage, lowered solute potential, and higher accumulation of proline and polyphenol contents indicated elevated CO2-induced abiotic stress tolerance in Suaeda. Higher activity of antioxidant enzymes in both species at both levels of CO2 help plants to combat the oxidative stress. Upregulation of NADP-dependent malic enzyme and NADP-dependent malate dehydrogenase genes indicated their role in abiotic stress tolerance as well as photosynthetic carbon (C) sequestration. Operation of C4 type CO2 fixation in S. monoica and an intermediate CO2 fixation in S. fruticosa could be the possible reason for the superior photosynthetic efficiency of S. monoica under stress conditions at elevated CO2. 相似文献
18.
The activity of ribulose-l,5-diphosphate carboxylase (RudiP-carboxylase) and phosphoenolpyruvate carboxylase (PEP-carboxylase) measured in vitro was independent from the chlorophyll content of the leaves. The relatively high activity of PEP-carboxylase as compared to the RudiP-carboxylase activity was particularly pronounced in the mutants. Realization of the potential ( in vitro measured) carboxylating activities in fixation of CO 2in vivo was practically complete in normal leaves. In the mutants, however, CO 2 fixation was lower than the level permitted by the carboxylase activity. This could be explained only in part by the impaired rate of photophosphorylation. Compartmentation of PEP-carboxylase was different in normal and mutant leaves: in contrast to the normal ones, parenchyma-sheath cells of the mutants exhibited high PEP-carboxylase activity. Competition of PEP-carboxylase with RudiP-carboxylase for CO 2 in the mutants led to accumulation of organic acids, and can account for their low photosynthetic activity. 相似文献
19.
The pathway of carbon assimilation in greening roots was compared to the pathway in leaves of Lens culinaris seedlings by means of labelling distribution analysis among the products of 14CO 2 fixation in vivo, and in vitro with ribulose 1,5-diphosphate as the substrate. In green leaves, CO 2 fixation via ribulose 1,5-diphosphate carboxylase predominated largely while, in green roots, this carboxylase activity and the phosphoenolpyruvate carboxylase contributed almost equally to the whole in vivo CO 2 fixation. A participation of the activities of both carboxylases according to the double carboxylation pathway in the synthesis of dicarboxylic acids (malate and aspartate) was demonstrated in vitro after 48 h of greening in roots but seemed to be absent in in vivo experiments. 相似文献
20.
Abstract Photosynthetic properties of cell suspension cultures derived from the callus proliferation of cladophyll explants of Chamaecereus sylvestrii Spegazzini were studied. High content of chlorophyll (105–120 μg/g fresh weight), cyanide sensitive O 2 uptake and maximal rates of O 2 evolution (100–115 μmol/mg Chl x h) and CO 2 fixation (130–150 μmol/mg Chl x h) were some of the properties of the exponential phase cells. Determination of the component reactions, viz. photosystems I and II and photophosphorylation of the chloroplasts isolated from the cells, indicated normal development and functioning of the photosynthetic machinery. Studies on the enzymatic reactions as well as the determination of the early products of 14CO 2 fixation in light in these cells implicated the operation of both autotrophic and non-auto-trophic pathways, the latter being less pronounced. The diurnal oscillation of titratable acidity and malate content found in the intact cladophyll tissues was absent in the cultured cells. Evidences for a rapid and continuous drain of carbon from malate into the citrate and isocitrate components of the TCA cycle via pyruvate after decarboxylation, and then into the amino acid pool are presented. The absence of large vacuoles and the rapid turnover of malate are considered to account for the lack of diurnal fluctuation of organic acide in the cell cultures. 相似文献
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