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1.
Birgitta Bergman 《Archives of microbiology》1984,137(1):21-25
A release of ammonium by non-nitrogen-fixing Anabaena cylindrica (grown on NH4Cl) in the presence of MSX (methionine sulfoximine) and absence of any external nitrogen source was found. In the light the release was maximal at 0.2 mM MSX, a concentration which did not affect net CO2 fixation nor the glycollate excretion, but inhibited the glutamine synthetase activity and the reassimilation of ammonium. It is suggested that the major source of the ammonium released is the photorespiratory conversion of glycine to serine as (1) the release was stimulated by increase in light intensity, (2) high CO2 (3%) lowered the release, if not given as a longer pretreatment (as CO2 or HCO
3
-
) when a stimulation was observed, (3) glyoxylate and glutamate stimulated the release, the latter compound particularly under nitrogen-deficient conditions and (4) isonicotinic acid hydrazide caused a reduced release of ammonium. Furthermore, a substantial part of the ammonium released by N2-fixing A. cylindrica in presence of MSX may thus originate from the glycollate pathway. The data show that in the light the glycine to serine conversion is active in cyanobacteria with a concomitant production of ammonium which is assimilated by glutamine synthetase.Abbreviations MSX
L-methionine-Dl-sulfoximine
- INH
isonicotinic acid hydrazide
- RuDP
ribulose 1,5-diphosphate
- Hepes
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- GS
glutamine synthetase
- GOGAT
glutamate synthase
- DTT
Dl-dithiothreitol 相似文献
2.
Dry weight and Relative Growth Rate of Lemna gibba were significantly increased by CO2 enrichment up to 6000 l CO2 l–1. This high CO2 optimum for growth is probably due to the presence of nonfunctional stomata. The response to high CO2 was less or absent following four days growth in 2% O2. The Leaf Area Ratio decreased in response to CO2 enrichment as a result of an increase in dry weight per frond. Photosynthetic rate was increased by CO2 enrichment up to 1500 l CO2 l–1 during measurement, showing only small increases with further CO2 enrichment up to 5000 l CO2 l–1 at a photon flux density of 210 mol m–2 s–1 and small decreases at 2000 mol m–1 s–1. The actual rate of photosynthesis of those plants cultivated at high CO2 levels, however, was less than the air grown plants. The response of photosynthesis to O2 indicated that the enhancement of growth and photosynthesis by CO2 enrichment was a result of decreased photorespiration. Plants cultivated in low O2 produced abnormal morphological features and after a short time showed a reduction in growth. 相似文献
3.
The phosphorylation state and the malate sensitivity of phosphoenolpyruvate carboxylase (PEPCase, EC 4.1.1.31) in Bryophyllum fedtschenkoi Hamet et Perrier are altered by changes in the ambient temperature. These effects, in turn alter the in-vivo activity of the enzyme. Low temperature (3 °C or less), stabilizes the phosphorylated form of the enzyme, while high temperature (30 °C) promotes its dephosphorylation. The catalytic activity of the phosphorylated and dephosphorylated forms of PEPCase increases with temperature, but the apparent K
i values for malate of both forms of the enzyme decrease. Results of experiments with detached leaves maintained in darkness in normal air indicate that the changes in malate sensitivity and phosphorylation state of PEPCase with temperature are of physiological significance. When the phosphorylated form of PEPCase is stabilized by reducing the temperature of leaves 9 h after transfer to constant darkness at 15 °C, a prolonged period of CO2 fixation follows. When leaves are maintained in constant darkness at 15 °C until CO2 output reaches a low steady-state level and the PEPCase is dephosphorylated, reducing the temperature to 3 °C results in a further period of CO2 fixation even though the phosphorylation state of PEPCase does not change.Abbreviations CAM
Crassulacean acid metabolism
- PEP
phosphoenolpyruvate
- PEPCase
phosphoenolpyruvate carboxylase
We thank the Agricultural and Food Research Council for financial support for this work. 相似文献
4.
Sándor Szabó Mihály Braun Péter Nagy Sándor Balázsy Otto Reisinger 《Hydrobiologia》2000,434(1-3):201-210
The decomposition of axenic Lemna gibba has been studied over a 200 day period under laboratory conditions in the presence and absence of wastewater micro-organisms. The residual mass of plant litter in the decomposition vessels decreased three times more rapidly under biotic than abiotic conditions. The organic matter in the duckweed litter lost about half its weight within 67.9 days in the presence of micro-organisms while more than 200 days were required in axenic vessels. In the former case, AFDW loss followed an exponential pattern of decay. The rate constant was 0.0102 day –1 and the decay was virtually complete after 200 days. The C and K concentration of the remaining duckweed litter decreased; the N, Ca, Fe and B concentration increased in both treatments. The concentration of total N, P, K, Mg, and Mo increased in the receiving water in both treatments but was much higher under biotic than abiotic conditions. Mass balances of nutrients in the vessels and flux of these nutrients between compartments in the vessels (duckweed litter, water and sediment) have been determined. Under axenic conditions the release of elements was very slow. Only notably potassium leaching had occurred. Leaching of potassium, magnesium and organic carbon took place mainly during the first term of incubation and then slowed down. Under biotic decomposition the elemental content of the litter decreased by more than 50% over 43 days for K, 53 days for Mo, 64 days for C, 81 days for Mg, 101 days for S, 104 days for P, 108 days for Na, 111 days for N, 140 days for B. Calcium and iron immobilised in the litter. Most of the released N, S, P, K, Mg and Mo remained in the water, but B and Mn settled into the sediment. The result of the investigation demonstrated that the nutrient flux from decomposing duckweed litter is mainly a microbially mediated process. 相似文献
5.
The relationship between ammonium assimilation and ammonium export has been studied in free-living, N2-fixing Rhizobium sp. 32H1. After 55 to 67 h of microaerobic growth under a gas phase of 0.2% O2 – 1.0% CO2 – 98.8% Ar high levels of nitrogenase were observed concomitant with a slightly adenylylated glutamine synthetase (GSI) and some glutamine synthetase (GSII) activity. However, after growth of 89 h, or longer, GSI became adenylylated and the level of GSII had decreased. When the gas phase was shifted to 0.2% O2 – 1.0% CO2 – 98.8% N2, a lag was observed before ammonium export could be detected in the 55 to 67 h cultures. No lag in ammonium export was observed in the cultures previously grown for 89 h. The onset of ammonium export in the 55 to 67 h cultures was found to correlate with the adenylylation state of GSI. There appeared to be no correlation between the level of GSII and the export of ammonium. Neither an increase in the adenylylation level of GSI nor ammonium export was observed when the 55 to 67 h cultures were maintained under the Ar gas mixture.Abbreviations GOGAT
Glutamate synthase
- GS
glutamine synthetase
- BES
[N,N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid]
- CTAB
cetyltrimethylammonium bromide
- MES
[2-(N-morpholino)-ethane sulfonic acid] 相似文献
6.
Detached leaves of Bryophyllum fedtschenkoi Hamet et Perrier kept in normal air show a single period of net CO2 fixation on transfer to constant darkness at temperatures in the range 0–25 °C. The duration of this initial fixation period is largely independent of temperature in the range 5–20 °C, but lengthens very markedly at temperatures below 4 °C, and is reduced at temperatures above 25 °C. The onset of net fixation of CO2 on transfer of leaves to constant darkness is immediate at low temperatures, but is delayed as the temperature is increased. The ambient temperature also determines whether or not a circadian rhythm of CO2 exchange occurs. The rhythm begins to appear at about 20 °C, is most evident at 30 °C and becomes less distinct at 35 °C. The occurrence of a distinct circadian rhythm in CO2 output at 30° C in the absence of a detectable rhythm in PEPCase kinase activity shows that the kinase rhythm is not a mandatory requirement for the rhythm of PEPCase activity. However, when it occurs, the kinase rhythm undoubtedly amplifies the PEPCase rhythm.Abbreviation PEPCase
phosphoenolpyruvate carboxylase
We thank the Agricultural and Food Research Council for financial support for this work. 相似文献
7.
Differential expression of individual genes encoding the small subunit of ribulose-1,5-bisphosphate carboxylase in Lemna gibba 总被引:9,自引:0,他引:9
Jane Silverthorne Charles F. Wimpee Takashi Yamada Stephen A. Rolfe Elaine M. Tobin 《Plant molecular biology》1990,15(1):49-58
The gene family encoding the small subunit (SSU) of ribulose-1,5-bisphosphate carboxylase/oxygenase in the monocot Lemna gibba contains approximately twelve members. We have isolated six of these genes from a genomic library, and sequenced five of the coding regions. The transit peptide nucleotide sequences are conserved, but less highly than the mature polypeptide coding sequence. The mature polypeptide amino acid sequences are identical to each other and to the sequence deduced from a cDNA clone derived from a seventh gene. Each of the five fully characterized genomic sequences contains a single intron in precisely the same position as the second intron of several dicots. The intron sequences differ in length and are less conserved than the coding sequences.The 3-untranslated regions of the different genes have been sequenced and used to prepare gene-specific probes. These probes have been used to study the expression levels of individual rbcS sequences. Expression of six of the seven genes can be detected in total RNA isolated from plants grown in continuous light. The levels of RNA encoded by each expressed gene are regulated by the action of phytochrome, but there is variability in the amount of expression of each RNA. 相似文献
8.
9.
Jaime E. Padilla Francisco Campos Víctor Conde Miguel Lara Federico Sánchez 《Plant molecular biology》1987,9(1):65-74
Glutamine synthetase expression was studied in developing root-nodules of common bean with regard to the time-course of specific activity, antigen accumulation, polypeptide composition and in vitro translation products. This analysis shows that the nodule-specific GS polypeptide (GS-gamma) is detected prior to the nitrogenase acetylene-reducing activity, and that its accumulation together with that of the GS-alpha and GS-beta polypeptides vary with nodule age. GS-gamma is present in ineffective nodules, although in a lower ratio to GS-beta than in wild-type nodules. Comparisons of in vitro translated and in vivo synthesized GS polypeptides suggest no post-translational modifications. The possible factors and mechanisms involved in the regulation of expression of GS polypeptides are discussed. 相似文献
10.
Methionine sulfoximine provided at a concentration which inhibits photosynthesis in intact leaves (10 mM) had no significant influence on the rate of photosynthesis of isolated pea leaf chloroplasts. In contrast, ammonium, 3-(3,4-dichlorophenyl)-1,1-dimethylurea, and D,L-glyceraldehyde all strongly inhibited the photosynthesis of isolated chloroplasts. We conclude that low concentrations of methionine sulfoximine (up to 10 mM) have no direct effect on the photosynthetic process. 相似文献
11.
Katsumi Higashi Hiroshi Kamada Hiroshi Harada 《Plant Cell, Tissue and Organ Culture》1996,45(2):109-114
The addition of l-glutamine, -alanine or l-glutamic acid strongly stimulates somatic embryo formation in carrot, not only in the number of somatic embryos formed but also with respect to their development. The effects of the amino acids on somatic embryogenesis were stronger than that of ammonium ion. In particular, l-glutamine strongly stimulated the development of somatic embryos. To clarify the different effects of amino acids and ammonium ion, the activity of glutamine synthetase (GS; EC 6.3.1.2), a key enzyme involved in nitrogen assimilation, was measured. Its activity decreased during the later stages of embryo development.Abbreviations -Ala
-alanine
- Glu
l-glutamic acid
- Gln
l-glutamine
- 2,4-D
2, 4-dichlorophenoxyacetic acid
- -GHA
l-glutamic acid -monohydroxamate
- GS
glutamine synthetase
- MS medium
Murashige & Skoog (1962) medium
- MS-NH4 medium
MS medium without NH4NO3
- MS+NH4 medium
MS-NH4 medium with 10 mM NH4Cl
- MS+ala medium
MS-NH4 medium with 10 mM -alanine
- MS+GLU medium
MS-NH4 medium with 10 mM l-glutamic acid
- MS+GLN medium
MS-NH4 medium with 10 mM l-glutamine
- NIR
nitrite reductase
- NR
nitrate reductase 相似文献
12.
Rosemarie Langenfeld-Heyser Bruno Schella Kirsten Buschmann Frieder Speck 《Trees - Structure and Function》1996,10(4):255-260
Microautoradiography indicated that 1-year-oldFraxinus excelsior L. stem chlorenchyma assimilated external14CO2 in mid-April, when buds were swollen, but before bud-break. The lenticel regions showed the highest amount of radioactively labeled assimilates. Labeled assimilates declined in the tangential direction with increasing distance from lenticels, suggesting that14CO2 entered the stem through the open intercellular spaces of lenticels. In the radial direction, the amount of radioactively labeled assimilates did not constantly decline with growing distance from the lenticel entrance. It was high in all lenticel phelloderm cells, which had high chlorophyll autofluorescence and very small starch grains, highest in the adjacent 4–6 rows of chlorenchyma, which had larger starch grains that increased in size towards the interior rows, and much lower in the inner cortex chlorenchyma, which had large starch grains. We suggest that the main function of the lenticel chlorenchyma (lenticel phelloderm plus 4–6 rows of adjacent cortex chlorenchyma) is the refixation of respiratory CO2 which could easily leave the stem intercellular spaces, rather than the fixation of external CO2. The lenticel chlorenchyma could reduce the loss of respiratory CO2 by its photosynthetic activity. 相似文献
13.
1. The carbon isotope discrimination properties of a representative of each of the three types of photosynthetic bacteria Chlorobium thiosulfatophilum, Rhodospirillum rubrum and Chromatium and of the C3-alga Chlamydomonas reinhardii were determined by measuring the ratio of 13CO2 to 12CO2 incorporated during photoautotrophic growth. 2. Chromatium and R. rubrum had isotope selection properties similar to those of C3-plants, whereas Chlorobium was significantly different. 3. The results suggest that Chromatium and R. rubrum assimilate CO2 mainly via ribulose 1,5-diphosphate carboxylase and the associated reactions of the reductive pentose phosphate cycle, whereas Chlorobium utilizes other mechanisms. Such mechanisms would include the ferredoxin-linked carboxylation enzymes and associated reactions of the reductive carboxylic acid cycle.Abbreviations RuDP
ribulose 1,5-disphosphate
- PEP
phosphoenolpyruvate 相似文献
14.
Jacqueline Freeman Antonio J. Marquez Roger M. Wallsgrove Ritva Saarelainen Brian G. Forde 《Plant molecular biology》1990,14(3):297-311
A barley leaf cDNA library has been screened with two oligonucleotide probes designed to hybridize to conserved sequences in glutamine synthetase (GS) genes from higher plants. Two GS cDNA clones were identified as hybridizing strongly to one or both probes. The larger clone (pcHvGS6) contained a 1.6 kb insert which was shown by primer extension analysis to be an almost full-length cDNA. Both clones were more closely related to cDNAs for the chloroplast form of GS (GS2) from pea and Phaseolus vulgaris than to cDNAs for the cytosolic form (GS1). A sequence identicalto an N-terminal sequence determined from a purified preparation of the mature GS2 polypeptide (NH2-XLGPETTGVIQRMQQ) was found in the pcHvGS6-encoded polypeptide at residues 46–61, indicating a pre-sequence of at least 45 amino acids. The pre-sequence has only limited sequence homology to the pre-sequences of pea and P. vulgaris GS2 subunits, but is similarly rich in basic residues and possesses some of the structural features common to the targeting sequences of other chloroplast proteins. The molecular lesions responsible for the GS2-deficient phenotypes of eight photorespiratory mutants of barley were investigated using a gene-specific probe from pcHvGS6 to assay for GS2 mRNA, and an anti-GS antiserum to assay for GS2 protein. Three classes of mutants were identified: class I, in which absence of cross-reacting material was correlated with low or undetectable levels of GS2 mRNA; class II, which had normal or increased levels of GS2 mRNA but very little GS2 protein; and class III, which had significant amounts of GS2 protein but little or no GS2 activity. 相似文献
15.
The substrate specificity factor, V
cKo/VoKc, of spinach (Spinacia oleracea L.) ribulose 1,5-bisphosphate carboxylase/oxygenase was determined at ribulosebisphosphate concentrations between 0.63 and 200 M, at pH values between 7.4 and 8.9, and at temperatures in the range of 5° C to 40° C. The CO2/O2 specificity was the same at all ribulosebisphosphate concentrations and largely independent of pH. With increasing temperature, the specificity decreased from values of about 160 at 5° C to about 50 at 40° C. The primary effects of temperature were on K
c [Km(CO2)] and V
c [Vmax (CO2)], which increased by factors of about 10 and 20, respectively, over the temperature range examined. In contrast, K
o [Ki (O2)] was unchanged and V
o [Vmax (O2)] increased by a factor of 5 over these temperatures. The CO2 compensation concentrations () were calculated from specificity values obtained at temperatures between 5° C and 40° C, and were compared with literature values of . Quantitative agreement was found for the calculated and measured values. The observations reported here indicate that the temperature response of ribulose 1,5-bisphosphate carboxylase/oxygenase kinetic parameters accounts for two-thirds of the temperature dependence of the photorespiration/photosynthesis ratio in C3 plants, with the remaining one-third the consequence of differential temperature effects on the solubilities of CO2 and O2.Abbreviations RuBPC/O(ase)
ribulose 1,5-bisphosphate carboxylase/oxygenase
- RuBP
ribulose 1,5-bisphosphate
-
CO2 compensation concentration 相似文献
16.
The active species of CO2, i.e. CO2 or HCO
3
-
, formed in the CO dehydrogenase reaction was determined using the pure enzyme from the carboxydotrophic bacterium Pseudomonas carboxydovorans. Employing an assay system similar to that used to test for carbonic anhydrase, data were obtained which are quite compatible with those expected if CO2 is the first species formed. In addition, carbonic anhydrase activity was not detected in P. carboxydovorans. 相似文献
17.
Effects of CO2-mediated changes in paper birch and white pine chemistry on gypsy moth performance 总被引:3,自引:0,他引:3
We examined the effects of CO2-mediated changes in the foliar chemistry of paper birch (Betula papyrifera) and white pine (Pinus strobus) on performance of the gypsy moth (Lymantria dispar). Trees were grown under ambient or enriched CO2 conditions, and foliage was subjected to plant chemical assays and insect bioassays. Enriched CO2 atmospheres reduced foliar nitrogen levels and increased condensed tannin levels in birch but not in pine. Foliar carbohydrate concentrations were not markedly altered by CO2 environment. Gypsy moth performance was significantly affected by CO2 level, species, and the CO2 x species interaction. Under elevated CO2 conditions, growth was reduced for larvae fed birch, while development was prolonged for larvae fed pine. Although gypsy moths performed better overall on birch than pine, birch-fed larvae were influenced more by CO2-mediated changes in host quality. 相似文献
18.
Earlier labeling experiments have shown that autotrophically grown Acetobacterium woodii assimilates cell carbon via direct acetyl CoA formation from 2 CO2, rather than via the Calvin cycle. Cell extracts contained the enzymes required for biosynthesis starting from acetyl CoA and CO2. Notably, pyruvate synthase, pyruvate phosphate dikinase, and phosphoenolpyruvate carboxytransphosphorylase were present in sufficiently high activities. Ribulose-1,5-bisphosphate carboxylase activity could not be detected. The observed enzyme pattern was consistent with the postulated biosynthetic pathway as deduced from 14C-labeling experiments. 相似文献
19.
Chlorofluexus aurantiacus OK-70 fl was grown photoautotrophically with hydrogen as the electron source. The lowest doubling time observed was 26 h.The mechanism of CO2 fixation in autotrophically grown cells was studied. The presence of ribulose-1,5-bis-phosphate carboxylase and phosphoribulokinase could not be demonstrated. Carbon isotope fractionation (13C) was small, and alanine and aspartate but not 3-phosphoglycerate were the major labelled compounds in short term 14CO2 labelling. Thus CO2 is not fixed by the Calvin cycle.Fluoroacetate (FAc) completely inhibited protein synthesis in cultures and caused a slight citrate accumulation. However, CO2 fixation continued and increased polyglucose formation occurred. Under these conditions added acetate was metabolized to polyglucose, as were glycine, serine, glyoxylate and succinate, but to a lesser extent; little or no formate or CO was utilised.Glyoxylate inhibited CO2 fixation in vivo, indicating that pyruvate is formed from acetyl-CoA and CO2 by pyruvate synthase. Two key enzymes of the reductive TCA cycle, citrate lyase and -ketoglutarate synthase were not detected in cell free extracts, but pyruvate synthase and phosphoenolpyruvate carboxylase were demonstrated. It is concluded that acetyl-CoA is a central intermediate in the CO2 fixation process, but the mechanism of its synthesis is not clear.Abbreviations Rubisco
ribulose-1,5-bisphosphate carboxylase
- TCA cycle
tricarboxylic acid cycle
- FAc
monofluoroacetate
- PEP
phosphoenolpyruvate
- MV
methyl viologen
- TTC
triphenyltetrazolium chloride
- PMS
phenazine methosulfate 相似文献
20.
Control of photosynthesis in barley mutants with reduced activities of glutamine synthetase and glutamate synthase 总被引:4,自引:0,他引:4
Heterozygous mutants of barley (Hordeum vulgare L. cv. Maris Mink) with decreased activities of chloroplastic glutamine synthetase (GS) between 97 and 47% of the wild type and ferredoxin dependent glutamate synthase (Fd-GOGAT) down to 64% of the wild type have been used to study aspects of glyoxylate metabolism and the effect of glyoxylate on the activation state of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) in vivo. In the leaf, the extractable activities of serine:glyoxylate aminotransferase decreased with a decrease in GS whereas activities of glutamate and alanine:glyoxylate aminotransferase increased, pointing to a re direction of amino donors from serine to glutamate and alanine. Under ambient conditions, the leaf contents of glutamate and alanine declined continuously with a decrease in GS, in parallel with the decrease in total amino acids. Glycine, serine and asparagine contents decreased with a decrease in GS to approximately 70% of the wild type, but increased again with a further decrease in GS. At high irradiances and at low CO2 concentrations, glyoxylate contents exhibited a pronounced minimum between 60% and 80% GS. With a further decrease in GS, glyoxylate contents recovered and approached values similar to the wild type. The activation state of Rubisco showed a negative correlation with glyoxylate contents, indicating that a decrease in GS feeds back on the first step of carbon assimilation and photorespiration. The activation state of stromal fructose-1,6-bisphosphatase was unaffected by a decrease in GS or Fd-GOGAT, whereas the activation state of NADP dependent malate dehydrogenase changed in a complex manner. The CO2photocompensation point, *, was appreciably increased in mutants with 47% GS. Mitochondrial respiration in the light (Rd) was reduced with a decrease in GS. Relative rates of CO2 release into CO2-free air between the wild type and the 47%-GS mutant correlated with determinations of *. These data are consistent with the view that when GS is decreased there is an increased oxidative decarboxylation of glyoxylate resulting from a decreased availability of amino donors for the transamination of glyoxylate to glycine, and that when GS activities are lower than 70% of the wild type an additional mechanism operates to reduce the photorespiratory loss of ammonia.Abbreviations AGAT
nine:glyoxylate aminotransferase
- FBPase
fructose-1,6-bisphosphatase
- Fd-GOGAT
ferredoxin dependent glutamate synthase
- GGAT
glutamate:glyoxylate aminotransferase
- GS
glutamine synthetase
- MDH
malate dehydrogenase
- PFD
photon flux density
- Rubisco
ribulose-1,5-bisphosphate carboxylase-oxygenase
- SGAT
serine:glyoxylate aminotransferase
This research was supported by the Biotechnology and Biological Sciences Research Council initiative on the Biochemistry of Metabolic Regulation in Plants (PG 50/555). 相似文献