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1.
Klára Barabás László Zimányi Győző Garab 《Journal of bioenergetics and biomembranes》1985,17(6):365-373
The flash-induced electrochromic absorbance change (A
515) was measured in leaves of higher plants in the absence and presence of continuous monochromatic background illumination of different intensities and wavelengths. The variation of the amplitude of A
515 in background light was used to estimate the steady-state turnover time of the electron transport. In red light we obtained about 5 msec which was accounted for by the turnover of the linear electron transport. With far red background illumination or in the presence of the photosystem 2 inhibitor, DCMU, the steady-state turnover time tentatively assigned to photosystem 1 cyclic electron transport was much larger (100 msec).Increasing the intensity of background illumination with far red light gradually diminished the slow rise of A
515 in parallel with suppression of the initial rise generated by photosystem 1. At high intensities of the red light, however, while A
515 was attenuated, the slow rise was not eliminated and its proportion relative to the initial rise did not vary appreciably. 相似文献
2.
We investigated the frequency-dependence of the flash-induced electrochromic absorbance change, A515, and of the pH-indicating absorbance change of neutral red in isolated intact chloroplasts. The energization pattern of thylakoids depended strongly on the frequency (f) of the exciting flashes, tested between 0.05 and 2 s–1. When the frequency was increased from 0.1 to 1 s–1 the total initial change and the slow rise of A515 decreased by about 30% and 70%, respectively, and both the slow rise and decay were considerably accelerated. These changes were fully reversible, even after prolonged excitation at 1 s–1, if the frequency was decreased again to 0.1 s–1. Accumulation of an appreciable transmembrane electric field strength could not be detected in any of our experiments, at high frequency, since the decay of A515 was considerably accelerated when the frequency was increased. In contrast, pH significantly increased at higher frequencies of the exciting flashes. In the steady-state (after about 100 flashes) pH was about 0.5–0.8 pH unit higher than in the dark or at low frequencies. In the presence of nigericin or dithionite, both of which prevented accumulation of protons in the lumen, the total initial change in A515 at f=1 s–1 relative to that at f=0.1 s–1 decreased to a similar extent as in the control. The proportion of the slow rise relative to the initial amplitude, however, did not decrease. Our data support the suggestion that pH controls the amplitude of the slow rise of A515. However, contrary to a previous statement (B. Bouges-Bouquet (1981) Biochim. Biophys. Acta 535, 327–340), we show that the pH effect cannot be accounted for by variation of the rate of this kinetic component of A515.Abbreviations DCMU
3(3,4-dichlorophenyl)-1,1-dimethylurea
- f
frequency of the exciting flashes
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid
- PS
photosystem 相似文献
3.
Down-regulation of linear and activation of cyclic electron transport during drought 总被引:11,自引:0,他引:11
The effects of short-term drought on the regulation of electron transport through photosystems I and II (PSI and PSII) have been studied in Hordeum vulgare L. cv. Chariot. Fluorescence measurements demonstrated that electron flow through PSII decreased in response to both drought and CO2 limitation. This was due to regulation, as opposed to photoinhibition. We demonstrate that this regulation occurs between the two photosystems—in contrast to PSII, PSI became more oxidised and the rate constant for P700 re-reduction decreased under these conditions. Thus, when carbon fixation is inhibited, electron transport is down-regulated to match the reduced requirement for electrons and minimise reactive oxygen production. At the same time non-photochemical quenching (NPQ) increases, alleviating the excitation pressure placed on PSII. We observe an increase in the proportion of PSI centres that are active (i.e. can be oxidised with a saturating flash and then rapidly re-reduced) under the conditions when NPQ is increased. We suggest that these additional centres are primarily involved in cyclic electron transport, which generates the pH to support NPQ and protect PSII.Abbreviations
A
assimilation rate
- Ci
internal CO2 concentration
- ETC
electron transport chain
-
g
stomatal conductance
- FR
far red
-
k
pseudo first-order rate constant for the reduction of oxidised P700
- NPQ
non-photochemical quenching
- P700
primary electron donor of photosystem I
- PSI, PSII
photosystem I, II
- qP
proportion of open PSII centres
- ROS
reactive oxygen species
- pH
pH gradient across the thylakoid membrane
- PSII
quantum yield of photosystem II
An erratum to this article can be found at 相似文献
4.
Jacque Topf Huashi Gong Rina Timberg Laurence Mets Itzhak Ohad 《Photosynthesis research》1992,32(1):59-69
Photoinhibition of Photosystem II in unicellular algae in vivo is accompanied by thylakoid membrane energization and generation of a relatively high pH as demonstrated by 14C-methylamine uptake in intact cells. Presence of ammonium ions in the medium causes extensive swelling of the thylakoid membranes in photoinhibited Chlamydomonas reinhardtii but not in Scenedesmus obliquus wild type and LF-1 mutant cells. The rise in pH and the related thylakoid swelling do not occur at light intensities which do not induce photoinhibition. The rise in pH and membrane energization are not induced by photoinhibitory light in C. reinhardtii mutant cells possessing an active Photosystem II but lacking cytochrome b6/f, plastocyanin or Photosystem I activity and thus being unable to perform cyclic electron flow around Photosystem I. In these mutants the light-induced turnover of the D1 protein of Reaction Center II is considerably reduced. The high light-dependent rise in pH is induced in the LF-1 mutant of Scenedesmus which can not oxidize water but otherwise possesses an active Reaction Center II indicating that PS II-linear electron flow activity and reduction of plastoquinone are not required for this process. Based on these results we conclude that photoinhibition of Photosystem II activates cyclic electron flow around Photosystem I which is responsible for the high membrane energization and pH rise in cells exposed to excessive light intensities.Abbreviations cyt b6/f
cytochrome b6/f
- Diuron
3-(3,4-dichlorophenyl)-1 dimethyl urea
- QB
the secondary quinone acceptor of reaction center II
- DNP
2,4,Dinitrophenol
- FCCP
carbonyl cyanide trifluoromethoxy phenylhydrazone
- SDS-PAGE
sodium dodecylsulfate polyacrylamide gel electrophoresis 相似文献
5.
Ashok?Jadhav Elizabeth-France?Marillia Vivijan?Babic E.?Michael.?Giblin Edgar?B.?Cahoon Anthony?J.?Kinney Elzbieta?Mietkiewska Jennifer?M.?Brost David?C.?Taylor
Seed oils of meadowfoam (Limnanthes douglasii, L. alba) contain very long-chain fatty acids of strategic importance for a number of industrial applications. These include the monoene 20 15 and the diene 22:25,13. Engineering of meadowfoam-type oils in other oilseed crops is desirable for the production of these fatty acids as industrial feedstocks. Accordingly, we have targeted Brassica carinata and soybean (Glycine max) to trangenically engineer the biosynthesis of these unusual fatty acids. An L. douglasii seed-specific cDNA (designated Lim Des5) encoding a homolog of acyl-coenzyme A desaturases found in animals, fungi and cyanobacteria was expressed in B. carinata, which resulted in the accumulation of up to 10% 22:25,13 in the seed oil. In soybean, co-expression of Lim Des5 with a cDNA (Lim FAE1) encoding an FAEl (elongase complex condensing enzyme) homolog from L. douglasii resulted in the accumulation of 20:15 to approximately 10% of the total fatty acids of seeds. The content of C20 and C22 fatty acids was also increased from <0.5% in non-transformed soybean seeds to >25% in seeds co-expressing the Lim. douglasii Des5 and FAE1 cDNAs. In contrast, expression of the Lim Des5 in Arabidopsis did not produce the expected 20:25,11 in the seed oil. Cumulatively, these results demonstrate the utility of soybean and B. carinata for the production of vegetable oils containing novel C20 and C22 fatty acids, and confirm that the preferred substrates of the Lim Des5 are 20:0 and 22:13, respectively. 相似文献
6.
Marc Drolet Luc Péloquin Yann Echelard Linda Cousineau A. Sasarman 《Molecular & general genetics : MGG》1989,216(2-3):347-352
7.
Summary A procedure to reconstitute CF0CF1 proteoliposomes by gel filtration through a Sephadex-column pre-equilibrated with valinomycin and potassium is described. Proteoliposomes reconstituted by this procedure catalyze an ATP-induced pH of 2.5 to 3.5 units. pH was measured with either 9-aminoacridine or with the pH indicator pyranine trapped inside the proteoliposomes. CF0CF1 proteoliposomes prepared by conventional techniques catalyzed an ATP-induced formation, but were unable to catalyze an ATP-induced pH even in the presence of valinomycin.The ATP-induced pH was sensitive to uncouplers and energy transfer inhibitors and was increased at low temperatures. It is suggested that ATP-induced pH was observed in these proteoliposomes due to the efficient removal of intravesicular ammonium introduced with the CF0CF1 preparation. The ammonium acted as an internal buffer, and thus prevented an observable pH formation. 相似文献
8.
9.
Sergei Andreev Igor Andreev Elena Nikolaeva Anna Petrukhina Vladimir Zemskov Mariam Vafina 《Letters in Peptide Science》1998,5(2-3):63-66
The V3 loop from HIV-1 envelope glycoprotein gp120 is involved in viral entry and determines the cellular tropism and HIV-1-induced cell–cell fusion. Earlier we have shown that V3 loop peptides representing the sequences of syncytia-inducing HIV strains have high membranotropic activity. These peptides caused the lysis of liposomes of various lipid compositions, could fuse negatively charged liposomes and induced hemolysis of erythrocytes. In contrast, peptides mimicking the sequences of non-syncytia-inducing viruses showed no lytic or fusion activities at the same concentrations. Now we have found that the V3 loop synthetic peptides containing the conserved GPGR region, derived from T-lymphotropic strains (BRU and MN), as opposed to peptides containing the GPGQ region, are able to cause a pronounced membrane permeabilization (dissipation of the pH and the of human peripheral blood lymphocytes, erythrocytes and plasma membrane vesicles at micromolar concentrations with a dose-dependent kinetics. Analysis of the secondary structures of the peptides by circular dichroism revealed conformational changes in V3 loop peptides depending on solvent hydrophobicity: from random coil in water to an -helix/-sheet conformation in trifluoroethanol. Such structural changes of the V3 loop together with the membrane insertion of the gp41 N-terminal fusion peptide may promote the formation of the fusion pore during virus–cell fusion. 相似文献
10.
Tree diversity change in remaining primary mixed-broadleaved Korean pine forest under climate change and human activities 总被引:2,自引:0,他引:2
Studying biodiversity change in existing typical ecosystems of the world under possible global climate change and local human activities is important for diversity conservation. An adapted forest dynamics model is used to simulate tree diversity change of the remaining primary mixed-broadleaved Korean pine forest (RPMKPF) in northeast China under global climate change and local human activities for the next 50 years. Human activities include logging, which removes all big trees (DBH > 50 cm), removing all individuals of each single species and all species of each functional type (shade tolerant, shade intolerant and medium type tree species). As results for RPMKPF, the index of tree diversity decreases under climate change, but it increases significantly under a combination of climate change and logging. Removing all individuals of each single species significantly affects the tree diversity of the ecosystem. After the removal of shade tolerant species, both and
c indices of tree diversity experience a significant change. The index decreases significantly under climate change when shade intolerant or medium type tree species are removed, but the
c index does not change significantly. The results of this study have implications for tree diversity management in RPMKPF under climate change and human activities. 相似文献
11.
The oxidation of the PQ-pool after illumination with 50 or 500 micromol quantam(-2)s(-1) was measured in isolated thylakoids as the increase in DeltaA(263), i.e., as the appearance of PQ. While it was not observed under anaerobic conditions, under aerobic conditions it was biphasic. The first faster phase constituted 26% or 44% of total reappearance of PQ, after weak or strong light respectively. The dependence on oxygen presence as well as the correlation with the rate of oxygen consumption led to conclusion that this phase represents the appearance of PQ from PQ(*-) produced in the course of PQH(2) oxidation by superoxide accumulated in the light within the membrane. 相似文献
12.
Y. A. Holthuijzen F. F. M. van Dissel-Emiliani J. G. Kuenen W. N. Konings 《Archives of microbiology》1987,147(3):285-290
Uptake of inorganic carbon (Ci) in the form of CO2 and/or HCO
3
-
was studied in the chemolithoautotroph Thiobacillus neapolitanus under energy (thiosulphate) or carbon (CO2) limitation. Uptake of C1 was found to be a metabolic energy dependent process since in the presence of uncouplers no uptake was observed. The accumulation level of Ci was higher in the CO2-limited cells (1000-to 1500-fold) in comparison to the thiosulphate-limited cells (500-to 800-fold). The process of uptake could be influenced by addition of ionophores. Inhibition of uptake and accumulation of Ci was found after addition of valinomycin which completely dissipated the electrical potential (). After addition of nigericin an increase in the uptake and accumulation of Ci was observed with a concomitant increase of the . These results suggest that the is the main driving force for uptake of Ci. However, uptake of Ci could never be found in the absence of electron transfer, or in cells in which the electron transfer chain was blocked by potassium cyanide. Electron transfer therefore appears to be an additional requirement for Ci uptake. Kinetic experiment on the uptake of inorganic carbon at different pH values suggest that CO2 is the carbon species taken up by T. neapolitanus.Abbreviations RuBisCO
ribulose-1,5-bisphosphate carboxylase
- DCCD
N,N1-dicyclohexylcarbodiimide
- CCCP
carbonyl cyanide m-chlorophenyl hydrazone
- FCCP
carbonyl cyanide p-trifluoro-methoxyphenyl hydrazone
- EDTA
sodium ethylene diamine tetraacetate 相似文献
13.
Ines Janssen Hermann Mucke Wolfgang Löffelhardt Hans J. Bohnert 《Plant molecular biology》1987,9(5):479-484
The 287-bp spacer and the flanking 3-end of the 16S- and 5-end of the 23S-rRNA genes of the cyanelles from Cyanophora paradoxa have been sequenced and compared with the corresponding regions of cyanobacteria and chloroplasts. The spacer contains the uninterrupted genes for tRNAile and tRNAala. All coding regions show high homology to their prokaryotic counterparts. At the 3-end of the 16S-rDNA a CCTCCTTT sequence has been identified which is complementary to putative ribosome binding sites observed immediately upstream of the coding region of cyanelle protein genes. 相似文献
14.
T. Hodgkin 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1981,59(2):79-82
Summary The total vegetative node number, rate of node production and number of sprouts over 13 mm diameter were recorded for 10 F1 Brussels sprout cultivars and 45 progenies derived by intercrossing and selfing them. Significant differences, resulting from additive gene action, were found between the 10 cultivars and between their progenies for both characters. For total node number there was also evidence of dominant gene action. Total node number and rate of node production were closely correlated as were total node number and the number of harvested sprouts. The factors causing differences in rate of node production are indicated and the relationship of this character to other Brussels sprout yield components is outlined. 相似文献
15.
This paper shows the importance of acid-base analyses and 13C measurements in the evaluation of the responses of Salvinia species' responses to different N sources. It also highlights the importance of these methodologies as potential tools in the study of differences between habitats and nutrient acquisition, particularly N. This study used three different species of Salvinia cultured in the absence of combined N or in the presence of either NO
inf3
sup–
or NH
inf4
sup+
as N sources. The interaction between NO
inf3
sup–
or NH
inf4
sup+
as N source and organic acid metabolism, and the information on diazotrophy from the organic acid measurements, were also examined. Nevertheless, the results presented may not be used per se to assign diazotrophy. Carboxylate (C-A) levels in the different Salvinia species are much lower than the norm for bryophytes and tracheophytes, consistent with previously published work on Azolla. This might be related to the aquatic life form of these plants, since they seem to have no potential to increase the availability of Fe or P by the acidification of their rooting medium (water) that a larger net synthesis of organic acids, with cation-H+ exchange, could achieve. 相似文献
16.
Acidification inside the vacuo-lysosome systems is ubiquitous in eukaryotic organisms and essential for organelle functions. The acidification of these organelles is accomplished by proton-translocating ATPase belonging to the V-type H+-ATPase superfamily. However, in terms of chemiosmotic energy transduction, electrogenic proton pumping alone is not sufficient to establish and maintain those compartments inside acidic. Current studies have shown that thein situ acidification depends upon the activity of V-ATPase and vacuolar anion conductance; the latter is required for shunting a membrane potential (interior positive) generated by the positively charged proton translocation. Yeast vacuoles possess two distinct Cl– transport systems both participating in the acidification inside the vacuole, a large acidic compartment with digestive and storage functions. These two transport systems have distinct characteristics for their kinetics of Cl– uptake or sensitivity to a stilbene derivative. One shows linear dependence on a Cl– concentration and is inhibited by 4,4-diisothiocyano-2,2-stilbenedisulfonic acid (DIDS). The other shows saturable kinetics with an apparentK
m
for Cl– of approximately 20 mM. Molecular mechanisms of the chemiosmotic coupling in the vacuolar ion transport and acidification inside are discussed in detail. 相似文献
17.
Kelder B Mukeji P Kirchner S Hovanec G Leonard AE Chuang LT Kopchick JJ Huang YS 《Molecular and cellular biochemistry》2001,219(1-2):7-11
Long-chain polyunsaturated fatty acids (LC-PUFA) are important components of cellular structure and function. Most of LC-PUFA are derived from linoleic acid and a-linolenic acid. In plants and fungi, these two acids can be synthesized from oleic acid via the action of two enzymes, 12 and 15-desaturases. Due to lack of these enzymatic activities and the ability to synthesize these two essential fatty acids, animals must obtain them from the diet. In this report, we demonstrated the expression of a fungal 12-desaturase gene in mouse L cells incubated in serum-free medium. The results showed a significant increase in the amount of linoleic acid with a concomitant decrease of oleic acid in cellular lipids. Most of the newly formed linoleic acid was incorporated into cellular phospholipids, particularly phosphatidylcholine. The increase of linoleic acid provided the substrate for the endogenous synthesis of (n-6) LC-PUFA, such as eicosadienoic acid (EDA), dihomo--linoleic acid (DGLA) and arachidonic acid (AA). Prolonged incubation further increased the levels of linoleic acid derived from oleic acid by the action of 12-desaturase, and the levels of 20:2n-6 produced from linoleic acid by the action of the endogenous elongase. However, prolonged incubation suppressed significantly the formation of DGLA and AA. In a separate study, a fungal 6-desaturase gene has also been expressed in the mouse L cells incubated in serum-containing medium. The result shows a significant increase in levels of 20:3n-6 and 20:4n-6. These findings demonstrate that through genetic modification, it is possible to (1) generate cell lines which no longer require dietary 'essential' fatty acids and (2) alter the endogenous fatty acid metabolism to enhance the production of LC-PUFA and their derivatives. 相似文献
18.
Hervé Minoux Nicolas Moitessier Yves Chapleur Bernard Maigret 《Letters in Peptide Science》1997,4(4-6):463-466
The aim of this work was to elucidate, usingmolecular modeling, structural and electrostaticcommon parameters of several selective fibrinogenreceptor antagonists. From this theoretical pattern,we are currently designing and synthesizing originalnon-peptidic and selective carbohydrate-basedantagonists of the fibrinogen receptor. 相似文献
19.
Etiolated seedlings developed at cold-hardening temperatures (5°C) exhibited etioplasts with considerable vesiculation of internal membranes compared to etioplasts developed at 20°C regardless of the osmotic concentration employed during sample preparation. This vesiculation disappeared during exposure to continuous light at 5°C. This transformation of 5°C and 20°C etioplasts to chloroplasts under continuous light at 5° and 20°C respectively proceeded normally with the initial development of non-appressed lamellae and the subsequent appearance of granal stacks. However, chloroplasts developed at 5°C exhibited fewer lamellae per granum than chloroplasts developed at 20°C.Although the polypeptide complements of etioplasts and chloroplasts developed at 5° or 20°C were not significantly different, monomeric light harvesting complex (LHCII3) was assembled into oligomeric light harvesting complex (LHCII1) during chloroplast biogenesis at 20°C (oligomer:monomer =1.8) whereas monomeric LHCII predominated at 5°C (oligomer:monomer =0.3). Low temperature fluorescence emission spectra of isolated thylakoids indicated that both the F685/F735 and F695/F735 were significantly higher after greening at 5°C than at 20°C. In addition, chloroplast biogenesis at 5°C was associated with a low ratio of trans-3-hexadecenoic acid (0.5) in phosphatidylglycerol whereas at 20°C biogenesis was associated with a high ratio (1.6). Comparative kinetics indicated that the maximization of the trans-3-hexadecenoic acid level precedes the assembly of monomeric LHCII into oligomeric LHCII during biogenesis at 20°C. It is suggested that low developmental temperatures modulate the assembly of LHCII by reducing the trans-3-hexadecenoic acid content of phosphatidylglycerol such that monomeric or some intermediate form of LHCII predominates.Abbreviations RH
Cold-hardened rye
- RNH
Non-hardened rye
- EF
Exoplasmic freeze fracture face
- Chl
Chlorophyll
- LHCII
Light harvesting Chl a/b protein complex
- LHCII1
Oligomeric form
- LHCII2
Dimeric form
- LHCII3
Monomeric form
- CPl
Chl a-protein complex associated with photosystem I
- CPa
Chl a-protein comples associated with photosystem II
- FP
Free pigment
- PSI
Photosystem I
- PSII
Photosystem II
- Trans-16:1
Trans-3-hexadecenoic acid
- 16:0
Palmitic acid
- 18:3
Linolenic acid
- PG
Phosphatidylglycerol
- PC
Phosphatidylcholine
- PE
Phosphatidylethanolamine
- SL
Sulfolipid
- DGDG
Digalactosyldiacylglycerol
- MGDG
Monogalactosyldiacylglycerol
- SDS
Sodium dodecyl sulfate
- PAGE
Polyacrylamide gel electrophoresis
- PLB
Prolamellar body
- A
Angstrom
- DOC
deoxycholate 相似文献
20.
Leaf mesophyll protoplasts of oat (Avena sativa L.) were allowed to fix 14C-labeled bicarbonate in the absence or presence of pyridoxal phosphate (PLP), a specific inhibitor of the phosphate translocator of the inner envelope membrane of chloroplasts. The incubation was terminated by a method of rapid integrated protoplast homogenization and fractionation, and compartmented levels of label contained in sugars, phosphate esters, amino acids and organic acids were determined. The results show that the addition of PLP to a suspension of intact protoplasts causes an accumulation of phosphate esters in the chloroplasts stroma for up to 2.5 min of incubation, with a corresponding decrease in the cytosol. Prolonged treatment of protoplasts with PLP in the light resulted in a decrease of starch-associated label, combined with higher levels of labeled sugars in the cytosol, indicating a switch from phosphorolytic to hydrolytic starch degradation. Together with the determination of pool sizes of triose phosphates and of inorganic phosphate, the results demonstrate that the method employed is an important tool in investigating processes of intracellular regulation. They are discussed with respect to the permeability and possible side reactions of PLP, as well as in the light of reports on PLP action on isolated chloroplasts.Abbreviations Pi
orthophosphate
- PLP
pyridoxal 5-phosphate
- TP
triosephosphate 相似文献