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1.
Cupric ion (Cu++) inhibits the rate of photosystem II electron transport and the intensity of the variable part of chl a fluorescence in isolated chloroplast thylakoids. The inhibition is markedly dependent on the nature of the buffer used in the assay medium. In MES and HEPES buffers, complete inhibition of photosystem II occurs at 30 M of Cu++, while in Tricine no inhibition occurred even at 200 M Cu++. In other buffers used (TES, Phosphate, Tris), the efficacy of Cu++ inhibition is intermediate. The calculated binding constants are found to correspond to the observed I50 values for the six buffers used. It is concluded that the previous reports on copper inhibition, where buffers have been used indiscriminately should be reconsidered. Certain reagents such as hydroxylamine, ascorbate and diphenyl carbazide, which react with Cu++, should be avoided.Abbreviations Chl
chlorophyll
- DCIP
2,6-dichlorophenol indophenol
- DCMU
3-(3,4 dichlorophenyl)-1,1-dimethyl urea
- DAD
diaminodurene
- DPC
diphenyl carbazide
- Fv
variable chl fluorescence
- HEPES
N-2-hydroxyethyl piperazine sulfonic acid
-
I
30
inhibitor concentration causing 30% inhibition of Fv
- MES
2-(N-morpholino) ethane sulfonic acid
- MV
Methyl viologen
- PS II
Photosystem II
- PS I
Photosystem I
- TES
N-tris(hydroxymethyl)-methyl-2-amino sulfonic acid
- TMPD
N,N,N,N-tetramethyl-p-phenylenediamine
- Tricine
N-tris(hydroxymethyl) ethylglycine
- Tris
N-tris(hydroxymethyl)amino ethane 相似文献
2.
Dmitry Shevela Gennady Ananyev Ann K. Vatland Janine Arnold Fikret Mamedov Lutz A. Eichacker G. Charles Dismukes Johannes Messinger 《Physiologia plantarum》2019,166(1):165-180
High solar flux is known to diminish photosynthetic growth rates, reducing biomass productivity and lowering disease tolerance. Photosystem II (PSII) of plants is susceptible to photodamage (also known as photoinactivation) in strong light, resulting in severe loss of water oxidation capacity and destruction of the water‐oxidizing complex (WOC). The repair of damaged PSIIs comes at a high energy cost and requires de novo biosynthesis of damaged PSII subunits, reassembly of the WOC inorganic cofactors and membrane remodeling. Employing membrane‐inlet mass spectrometry and O2‐polarography under flashing light conditions, we demonstrate that newly synthesized PSII complexes are far more susceptible to photodamage than are mature PSII complexes. We examined these ‘PSII birth defects’ in barley seedlings and plastids (etiochloroplasts and chloroplasts) isolated at various times during de‐etiolation as chloroplast development begins and matures in synchronization with thylakoid membrane biogenesis and grana membrane formation. We show that the degree of PSII photodamage decreases simultaneously with biogenesis of the PSII turnover efficiency measured by O2‐polarography, and with grana membrane stacking, as determined by electron microscopy. Our data from fluorescence, QB‐inhibitor binding, and thermoluminescence studies indicate that the decline of the high‐light susceptibility of PSII to photodamage is coincident with appearance of electron transfer capability QA? → QB during de‐etiolation. This rate depends in turn on the downstream clearing of electrons upon buildup of the complete linear electron transfer chain and the formation of stacked grana membranes capable of longer‐range energy transfer. 相似文献
3.
Effects of abscisic Acid treatment on the thermostability of the photosynthetic apparatus in barley chloroplasts 总被引:1,自引:0,他引:1
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Thermostability of the photosynthetic apparatus of abscisic acid (ABA)-treated seedlings of barley (Hordeum vulgare) was studied by light-scattering and by fluorescence measurements of isolated chloroplasts. ABA treatment markedly decreased heat damage of the chloroplast ultrastructure; an exogenous ABA concentration of 10−5 molar was most effective. Heat-induced increase of the 77 kilodalton fluorescence ratio F740/F685 was also smaller at this ABA concentration. The heat-induced increase of the initial chlorophyll fluorescence level (Fo) was virtually eliminated in ABA-treated (10−5 molar) chloroplasts up to 45°C and slightly increased at 50°C, relative to control chloroplasts where Fo increased even at 35°C and reached its maximal value at 45°C. In control chloroplasts, Fo increased with a 5-minute pretreatment temperature, an effect observed as low as 35°C. Fo was maximal at 45°C. In contrast, chloroplasts treated with 10−5 molar ABA did not exhibit a heat-induced increase in Fo until 50°C. 相似文献
4.
O. V. Polishchuk M. V. Vodka N. A. Belyavskaya A. P. Khomochkin E. K. Zolotareva 《Cell and Tissue Biology》2016,10(3):250-257
The ultrastructure and functional parameters of the photosynthetic apparatus in leaves of 14-day-old pea seedlings were studied in conditions of laboratory simulated acid rain (SAR). Pea seedlings were sprayed with an aqueous solution containing NaNO3 (0.2 mM) and Na2SO4 (0.2 mM) (pH 5.6, a control variant), or with the same solution, which was acidified to pH 2.5 (acid variant). Functional characteristics were determined by chlorophyll fluorescence analysis. There was reduction in the efficiency of the photosynthetic electron transport by 25% accompanied by an increase in the quantum yield of thermal dissipation of excess light quanta by 85% without significant change in maximum quantum yield of PSII photochemistry (Fv/Fm). Ultrastructural changes in chloroplasts were revealed by transmission electron microscopy (TEM) 2 days after the SAR treatment of pea leaves. In this case, changes in the structure of the grana and heterogeneity of the thylakoids packing in the granum, namely, an increase in thylakoid intraspace widths and thickness of granal thylakoids compared to the control, were found. It was shown also that carbonic anhydrase activity was significantly inhibited in chloroplast preparations isolated from SAR-treated pea leaves. We hypothesize possible involvement of chloroplast carbonic anhydrase in thylakoid granal structure maintenance. The structural disturbances and the inhibition of photochemical activity of chloroplasts are possible consequences of the carbonic anhydrase inactivation by SAR treatment leading to violation of HCO3 ?–CO2 equilibrium. The data obtained suggest that acid rains negatively affect the photosynthetic apparatus by disrupting the membrane system of the chloroplast. 相似文献
5.
Yi Liao Da-Quan Xu 《植物学报(英文版)》2007,49(4):523-530
After saturating light illumination for 3 h the potential photochemical efficiency of photosystem Ⅱ (PSII) (FJF,, the ratio of variable to maximal fluorescence) decreased markedly and recovered basically to the level before saturating light illumination after dark recovery for 3 h in both soybean and wheat leaves, indicating that the decline in FJ/Fm is a reversible down-regulation. Also, the saturating light illumination led to significant decreases in the low temperature (77 K) chlorophyll fluorescence parameters F685 (chlorophyll a fluorescence peaked at 685 nm) and F685/F735 (F735, chlorophyll a fluorescence peaked at 735 nm) in soybean leaves but not in wheat leaves. Moreover, trypsin (a protease) treatment resulted in a remarkable decrease in the amounts of PsbS protein (a nuclear gene psbS-encoded 22 kDa protein) in the thylakoids from saturating light-illuminated (SI), but not in those from darkadapted (DT) and dark-recovered (DRT) soybean leaves. However, the treatment did not cause such a decrease in amounts of the PsbS protein in the thylakoids from saturating light-illuminated wheat leaves. These results support the conclusion that saturating light illumination induces a reversible dissociation of some light-harvesting complex Ⅱ (LHClI) from PSII reaction center complex in soybean leaf but not in wheat leaf. 相似文献
6.
Inhibition of 3-Phosphoglycerate-Dependent O(2) Evolution by Phosphoenolpyruvate in C(4) Mesophyll Chloroplasts of Digitaria sanguinalis (L.) Scop 总被引:1,自引:1,他引:0
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The effects of phosphoenolpyruvate (PEP), inorganic phosphate (Pi), and ATP on 3-phosphoglycerate (PGA)-dependent O2 evolution by chloroplasts of Digitaria sanguinalis (L.) Scop. (crabgrass) were evaluated relative to possible mechanisms of PEP transport by the C4 mesophyll chloroplast. Crude and Percoll purified chloroplast preparations exhibited rates of PGA-dependent O2 evolution in the range of 90 to 135 micromoles O2 per milligram chlorophyll per hour, and up to 180 micromoles O2 per milligram chlorophyll per hour at optimal Pi concentrations (approximately 0.2 millimolar at 9 millimolar PGA). Higher concentrations of Pi were inhibitory. PEP inhibited O2 evolution (up to 70%) in both chloroplast preparations when the PEP to PGA ratio was high (i.e. 9 millimolar PEP to 0.36 millimolar PGA). Usually no inhibition was seen when the PEP to PGA ratio was less than 2. PEP acted as a competitive inhibitor and, at a concentration of 9 millimolar, increased the apparent Km (PGA) from 0.15 to 0.53 millimolar in Percoll purified chloroplasts. A low concentration of PGA and high ratio of PEP to PGA, which are considered unphysiological, were required to detect any inhibition of O2 evolution by PEP. Similar results were obtained from crude versus Percoll purified preparations. Neither the addition of Pi nor ATP could overcome PEP inhibition. As PEP inhibition was competitive with respect to PGA concentration, and as addition of ATP or Pi could not prevent PEP inhibition of PGA-dependent O2 evolution, the inhibition was not due to PEP exchange of adenylates or Pi out of the chloroplast. Analysis of the effect of Pi and PEP, separately and in combination, on PGA-dependent O2 evolution suggests interactions between PEP, Pi, and PGA on the same translocator in the C4 mesophyll chloroplast. C3 spinach chloroplasts were also found to be sensitive to PEP, but to a lesser extent than crabgrass chloroplasts. The apparent Ki values (PEP) were 3 and 21 millimolar for crabgrass and spinach, respectively. 相似文献
7.
P. G. LUO K. J. DENG X. Y. HU L. Q. LI X. LI J. B. CHEN H. Y. ZHANG Z. X. TANG Y. ZHANG Q. X. SUN F. Q. TAN Z. L. REN 《Plant, cell & environment》2013,36(3):683-696
CN17 is a functional stay‐green wheat variety that exhibits delayed leaf senescence and enhanced photosynthetic competence. To better understand these valuable traits, levels of chlorophyll a and b, soluble proteins, unsaturated fatty acids, and other components of CN17 were assayed. In addition, chloroplast ultrastructure, chloroplast number, and differences in gene expression between CN17 and a control variety, MY11, were examined. By 21 d post‐anthesis (DPA), CN17 leaves exhibited a significantly higher maximal photochemical efficiency for photosystem II (PSII) (F v /F m ) and a significantly higher efficiency of excitation capture by open PSII reaction centres (Fv′/Fm′). In addition, chlorophyll degradation in CN17 was delayed by approximately 14 d, and was not blocked as observed in cosmetic stay‐green phenotypes. The soluble protein content (Ps) of CN17 was higher than MY11 at all timepoints assayed, and the ratio of unsaturated to saturated fatty acids was significantly higher. CN17 also exhibited isolated granal lamellae associated with vesicles and diminished peroxidation, and between 35 and 42 DPA, a sharp decrease in chloroplast number was detected. Taken together, these results strongly support the hypothesis that chloroplast ultrastructure regeneration is responsible for the functional stay‐green trait of CN17, and gene expression data provide insight into the mechanistic details. 相似文献
8.
The cupric ion as an inhibitor of photosynthetic electron transport in isolated chloroplasts 总被引:7,自引:5,他引:2
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Strong inhibition of uncoupled photosynthetic electron transport by Cu2+ in isolated spinach chloroplasts was observed by measuring changes in O2 concentration in the reaction medium. Inhibition was dependent not only on the concentration of the inhibitor, but also on the ratio of chlorophyll to inhibitor. Binding of Cu2+ to the chloroplast membranes resulted in removal of Cu2+ from solution. When chloroplasts were exposed to preincubation in light, there was increased inhibition as a result of Cu2+ binding to inhibitory sites. Preincubation in the dark resulted in Cu2+ binding to noninhibitory sites and decreased inhibition. The degree of inhibition was lower at low light intensities than at high light intensities. 相似文献
9.
Biogenesis of water splitting by photosystem II during de‐etiolation of barley (Hordeum vulgare L.)
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Dmitriy Shevela Janine Arnold Veronika Reisinger Hans‐Martin Berends Karol Kmiec Sergey Koroidov Ann Kristin Bue Johannes Messinger Lutz A. Eichacker 《Plant, cell & environment》2016,39(7):1524-1536
Etioplasts lack thylakoid membranes and photosystem complexes. Light triggers differentiation of etioplasts into mature chloroplasts, and photosystem complexes assemble in parallel with thylakoid membrane development. Plastids isolated at various time points of de‐etiolation are ideal to study the kinetic biogenesis of photosystem complexes during chloroplast development. Here, we investigated the chronology of photosystem II (PSII) biogenesis by monitoring assembly status of chlorophyll‐binding protein complexes and development of water splitting via O2 production in plastids (etiochloroplasts) isolated during de‐etiolation of barley (Hordeum vulgare L.). Assembly of PSII monomers, dimers and complexes binding outer light‐harvesting antenna [PSII‐light‐harvesting complex II (LHCII) supercomplexes] was identified after 1, 2 and 4 h of de‐etiolation, respectively. Water splitting was detected in parallel with assembly of PSII monomers, and its development correlated with an increase of bound Mn in the samples. After 4 h of de‐etiolation, etiochloroplasts revealed the same water‐splitting efficiency as mature chloroplasts. We conclude that the capability of PSII to split water during de‐etiolation precedes assembly of the PSII‐LHCII supercomplexes. Taken together, data show a rapid establishment of water‐splitting activity during etioplast‐to‐chloroplast transition and emphasize that assembly of the functional water‐splitting site of PSII is not the rate‐limiting step in the formation of photoactive thylakoid membranes. 相似文献
10.
Ca2+-dependent influence of excess Cu2+ on the photosynthetic akpparatus monitored through chlorophyll fluorescence measurements was investigated in runner bean plants (Phaseolus coccineus L. cv. Pie kny Ja?) at three different growth stages. It was observed that the toxic effect of excess Cu2+ on plants depends both on their growth stages and the Ca2+ content in the medium. Increased Ca2+ content limits Cu2+ action on plants at their initial growth stage (I) through: stabilization of the PSII complex (increase of the ratio of variable to minimal fluorescence [Fv/F0]), improved electron flow and reoxidative processes of the quinone primary electron acceptor of PSII (QA) (increase of quantum yield of PSII electron transport [φe] and photochemical quenching of fluorescence [qP] values) and elimination of nonphotochemical energy dissipation (decrease of nonphotochemical fluorescence quenching from the Stern-Volmer equation [NPQ] and fraction of the absorbed light energy not used for photochemistry [LNU] values). At this growth stage excess Cu2+ decreases the rates of QA reduction as a result of decreased PSII activity at its donor side only at lower Ca2+ level. At the intermediate growth stage (II) the plants were less sensitive to Cu2+ treatment and also to changed Ca2+ content. A weakening of some photochemical processes by excess Cu2+ could be observed only at a higher Ca2+ dose. At the final growth stage of plants (III) Ca2+ ions exerted a decisively different effect on the mechanism of excess Cu2+ action on bean plants, visualized by decreased PSII stabilization and utilization of absorbed light energy at increased Ca2+ content in the medium. 相似文献
11.
The effect of copper on
photoinhibition of photosystem II in vivo was studied in
bean (Phaseolus vulgaris L. cv Dufrix). The plants were
grown hydroponically in the presence of various concentrations of
Cu2+ ranging from the optimum 0.3 μm
(control) to 15 μm. The copper concentration of leaves
varied according to the nutrient medium from a control value of 13 mg
kg−1 dry weight to 76 mg kg−1 dry weight.
Leaf samples were illuminated in the presence and absence of lincomycin
at different light intensities (500–1500 μmol photons
m−2 s−1). Lincomycin prevents the concurrent
repair of photoinhibitory damage by blocking chloroplast protein
synthesis. The photoinhibitory decrease in the light-saturated rate of
O2 evolution measured from thylakoids isolated from treated
leaves correlated well with the decrease in the ratio of variable to
maximum fluorescence measured from the leaf discs; therefore, the
fluorescence ratio was used as a routine measurement of photoinhibition
in vivo. Excess copper was found to affect the
equilibrium between photoinhibition and repair, resulting in a decrease
in the steady-state concentration of active photosystem II centers of
illuminated leaves. This shift in equilibrium apparently resulted from
an increase in the quantum yield of photoinhibition (ΦPI)
induced by excess copper. The kinetic pattern of photoinhibition and
the independence of ΦPI on photon flux density were not
affected by excess copper. An increase in ΦPI may
contribute substantially to Cu2+ toxicity in certain plant
species.Cu2+ is an essential micronutrient but in
excess is toxic for plants. It is a redox-active metal that functions
as an enzyme activator and is an important part of prosthetic groups of
many enzymes (for review, see Sandmann and Böger, 1983). Copper
concentrations in healthy plant tissues range from 5 to 20 mg
kg−1 dry weight. In
Cu2+-rich environments, accumulation of
Cu2+ in plant tissues depends on the species and
cultivar. Cu2+ seems to have several sites of
action, which vary among plant species. Toxic concentrations of
Cu2+ inhibit metabolic activity, which leads to
suppressed growth and slow development. Most Cu2+
ions are immobilized to the cell walls of roots or of mycorrhizal fungi
(Kahle, 1993).When the tolerance mechanisms in the root zone become overloaded,
Cu2+ is translocated by both the xylem and phloem
up to the leaves. Excess Cu2+ may replace other
metals in metalloproteins or may interact directly with SH groups of
proteins (Uribe and Stark, 1982). Cu2+-induced
free-radical formation may also cause protein damage (for review, see
Fernandes and Henriques, 1991; Weckx and Clijsters, 1996). High
concentrations of Cu2+ may catalyze the formation
of the hydroxyl radical from O2 and
H2O2. This
Cu2+-catalyzed Fenton-type reaction takes place
mainly in chloroplasts (Sandmann and Böger, 1980). The hydroxyl
radical may start the peroxidation of unsaturated membrane lipids and
chlorophyll (Sandmann and Böger, 1980), and these inhibitory
mechanisms might contribute to the observed inhibition of
photosynthetic electron transport by excess Cu2+
(Clijsters and Van Assche, 1985).The role of Cu2+ as an inhibitor of
photosynthetic electron transport has been studied in vitro. Both the
donor (Cedeno-Maldonado and Swader, 1972; Samuelsson and Öquist,
1980; Schröder et al., 1994) and acceptor (Mohanty et al., 1989;
Yruela et al., 1992, 1993, 1996a, 1996b; Jegerschöld et al.,
1995) sides of PSII have been proposed to be the most sensitive site
for Cu2+ action. On the donor side,
Cu2+ is thought to inhibit electron transport to
P680, the primary donor of PSII (Schröder et al., 1994). On the
acceptor side, Cu2+ interactions with the
pheophytin-QA-Fe2+-domain
or Cu2+-induced modifications in the amino acid
or lipid structure close to the QA- and
QB-binding sites have been suggested to cause the
inhibition of electron transport (Jegerschöld et al., 1995;
Yruela et al., 1996a, 1996b).Celeno-Maldonado and Swader (1972) noticed that preincubation of
chloroplasts in the light enhanced the
Cu2+-induced inhibition of electron transport,
and that PSII was more susceptible to this kind of inhibition than was
PSI. The hypothetical acceptor- and donor-side mechanisms of the
light-induced inhibition of electron transport, photoinhibition,
involve the same domains of attack as Cu2+. Both
acceptor- and donor-side photoinhibition trigger the D1 polypeptide of
the PSII reaction center for degradation (for review, see Aro et al.,
1993). The damaged D1 protein is degraded, and the recovery of PSII
activity needs de novo synthesis of D1 protein. Photoinhibition occurs
at all light intensities (Tyystjärvi and Aro, 1996); therefore,
the cycle of PSII photoinhibition, which is followed by degradation,
and, finally, resynthesis of the D1 protein, runs constantly in plant
cells in the light. If the photoinhibition-repair cycle is allowed to
run for some time at a constant light intensity, equilibrium is
reached. At equilibrium (steady state), all three reaction rates
(photoinhibition, D1 degradation, and D1 synthesis) are equal. Healthy
plants are often able to maintain a high steady-state concentration of
active PSII under widely varying light intensities. Even if the
concentration of active PSII is lowered by high light, the
concentration of D1 protein tends to stay fairly constant (Cleland et
al., 1990; Kettunen et al., 1991). In the bean (Phaseolus
vulgaris L.) plants used in this study the steady-state D1 protein
content remained almost constant even in the presence of excess
Cu2+.The effect of Cu2+ on photoinhibition in
vivo has been studied very little. Vavilin et al. (1995) suggest that
excess Cu2+ may slow the PSII repair cycle in the
green alga Chlorella pyrenoidosa, and Ouzounidou et al.
(1997) suggest that Cu2+ inhibits adaptation to
light in maize. In the current study we show that excess
Cu2+ induces a large increase in the rate
constant of photoinhibition in vivo in a higher plant. 相似文献
12.
Garstka M Venema JH Rumak I Gieczewska K Rosiak M Koziol-Lipinska J Kierdaszuk B Vredenberg WJ Mostowska A 《Planta》2007,226(5):1165-1181
The effect of dark-chilling and subsequent photoactivation on chloroplast structure and arrangements of chlorophyll–protein
complexes in thylakoid membranes was studied in chilling-tolerant (CT) pea and in chilling-sensitive (CS) tomato. Dark-chilling
did not influence chlorophyll content and Chl a/b ratio in thylakoids of both species. A decline of Chl a fluorescence intensity and an increase of the ratio of fluorescence intensities of PSI and PSII at 120 K was observed after
dark-chilling in thylakoids isolated from tomato, but not from pea leaves. Chilling of pea leaves induced an increase of the
relative contribution of LHCII and PSII fluorescence. A substantial decrease of the LHCII/PSII fluorescence accompanied by
an increase of that from LHCI/PSI was observed in thylakoids from chilled tomato leaves; both were attenuated by photoactivation.
Chlorophyll fluorescence of bright grana discs in chloroplasts from dark-chilled leaves, detected by confocal laser scanning
microscopy, was more condensed in pea but significantly dispersed in tomato, compared with control samples. The chloroplast
images from transmission-electron microscopy revealed that dark-chilling induced an increase of the degree of grana stacking
only in pea chloroplasts. Analyses of O-J-D-I-P fluorescence induction curves in leaves of CS tomato before and after recovery
from chilling indicate changes in electron transport rates at acceptor- and donor side of PS II and an increase in antenna
size. In CT pea leaves these effects were absent, except for a small but irreversible effect on PSII activity and antenna
size. Thus, the differences in chloroplast structure between CS and CT plants, induced by dark-chilling are a consequence
of different thylakoid supercomplexes rearrangements.
Dedicated to Prof. Zbigniew Kaniuga on the 25th anniversary of his initiation of studies on chilling-induced stress in plants. 相似文献
13.
Maciej Garstka Anna Dro?ak Ma?gorzata Rosiak Jan Henk Venema Ewa Simeonova Jerzy Dobrucki 《BBA》2005,1710(1):13-23
Changes in chloroplast structure and rearrangement of chlorophyll-protein (CP) complexes were investigated in detached leaves of bean (Phaseolus vulgaris L. cv. Eureka), a chilling-sensitive plant, during 5-day dark-chilling at 1 °C and subsequent 3-h photoactivation under white light (200 μmol photons m−2 s−1) at 22 °C. Although, no change in chlorophyll (Chl) content and Chl a/b ratio in all samples was observed, overall fluorescence intensity of fluorescence emission and excitation spectra of thylakoid membranes isolated from dark-chilled leaves decreased to about 50%, and remained after photoactivation at 70% of that of the control sample. Concomitantly, the ratio between fluorescence intensities of PSI and PSII (F736/F681) at 120 K increased 1.5-fold upon chilling, and was fully reversed after photoactivation. Moreover, chilling stress seems to induce a decrease of the relative contribution of LHCII fluorescence to the thylakoid emission spectra at 120 K, and an increase of that from LHCI and PSI, correlated with a decrease of stability of LHCI-PSI and LHCII trimers, shown by mild-denaturing electrophoresis. These effects were reversed to a large extent after photoactivation, with the exception of LHCII, which remained partly in the aggregated form. In view of these data, it is likely that dark-chilling stress induces partial disassembly of CP complexes, not completely restorable upon photoactivation. These data are further supported by confocal laser scanning fluorescence microscopy, which showed that regular grana arrangement observed in chloroplasts isolated from control leaves was destroyed by dark-chilling stress, and was partially reconstructed after photoactivation. In line with this, Chl a fluorescence spectra of leaf discs demonstrated that dark-chilling caused a decrease of the quantum yield PSII photochemistry (Fv/Fm) by almost 40% in 5 days. Complete restoration of the photochemical activity of PSII required 9 h post-chilling photoactivation, while only 3 h were needed to reconstruct thylakoid membrane organization and chloroplast structure. The latter demonstrated that the long-term dark-chilled bean leaves started to suffer from photoinhibition after transfer to moderate irradiance and temperature conditions, delaying the recovery of PSII photochemistry, independently of photo-induced reconstruction of PSII complexes. 相似文献
14.
Intact chloroplasts were obtained from mesophyll protoplasts isolated from Mesembryanthemum crystallinum in the C3 or Crassulacean acid metabolism (CAM) photosynthetic mode, and examined for the influence of inorganic phosphate (Pi) on aspects of bicarbonate-dependent O2 evolution and CO2 fixation. While the chloroplasts from both modes responded similarly to varying Pi, some features appear typical of chloroplasts from species capable of CAM, including a relatively high capacity for photosynthesis in the absence of Pi, a short induction period, and resistance to inhibition of photosynthesis by high levels of Pi. In the absence of Pi the chloroplasts retained 75–85% of the 14CO2 fixed and the total export of dihydroxyacetone phosphate was low compared with the rate of photosynthesis. In CAM plants the ability to conduct photosynthesis and retain most of the fixed carbon in the chloroplasts at low external Pi concentrations may enable storage of carbohydrates which are essential for providing a carbon source for the nocturnal synthesis of malic acid. At high external Pi concentrations (e.g. 10 25 mM), the amount of total dihydroxyacetone phosphate exported to the assay medium relative to the rate of photosynthesis was high while the products of 14CO2 fixation were largely retained in the chloroplasts which indicates starch degradation is occurring at high Pi levels. Starch degradation normally occurs in CAM plants in the dark; high levels of Pi may induce starch degradation in the light which has the effect of limiting export of the immediate products of photosynthesis and thus the degree of Pi inhibition of photosynthesis with the isolated chloroplast. 相似文献
15.
Karlický V. Podolinská J. Nadkanská L. Štroch M. Čajánek M. Špunda V. 《Photosynthetica》2010,48(3):475-480
The present study was conducted to examine changes in photosynthetic pigment composition and functional state of the thylakoid
membranes during the individual steps of preparation of samples that are intended for a separation of pigmentprotein complexes
by nondenaturing polyacrylamide gel electrophoresis. The thylakoid membranes were isolated from barley leaves (Hordeum vulgare L.) grown under low irradiance (50 μmol m−2 s−1). Functional state of the thylakoid membrane preparations was evaluated by determination of the maximal photochemical efficiency
of photosystem (PS) II (FV/FM) and by analysis of excitation and emission spectra of chlorophyll a (Chl a) fluorescence at 77 K. All measurements were done at three phases of preparation of the samples: (1) in the suspensions of osmotically-shocked broken chloroplasts, (2) thylakoid membranes in extraction buffer containing Tris, glycine, and glycerol and (3) thylakoid membranes solubilized with a detergent decyl-β-D-maltosid. FV/FM was reduced from 0.815 in the first step to 0.723 in the second step and to values close to zero in solubilized membranes.
Pigment composition was not pronouncedly changed during preparation of the thylakoid membrane samples. Isolation of thylakoid
membranes affected the efficiency of excitation energy transfer within PSII complexes only slightly. Emission and excitation
fluorescence spectra of the solubilized membranes resemble spectra of trimers of PSII light-harvesting complexes (LHCII).
Despite a disrupted excitation energy transfer from LHCII to PSII antenna core in solubilized membranes, energy transfer from
Chl b and carotenoids to emission forms of Chl a within LHCII trimers remained effective. 相似文献
16.
The interaction between photosynthetic electron transport and the activities of the thylakoid associated carbonic anhydrase (tCA), estimated as combined tCA activity in pea plants (Pisum sativum L. Borek cv., WT) and mutant form (costata 2/125) that differ in chlorophyll content have been compared. Chlorophyll a fluorescence changes after the inhibition of tCA by ethoxyzolamide (EZ), estimating possible role of tCA in PSII downregulation were investigated. Costata expresses higher tCA activity and higher O2 evolution in comparison to WT. Inhibition of tCA by EZ decreased effective PSII photochemistry that coincided with an enhancement in thermal dissipation, while maximal PSII quantum yield (Fv/Fm) did not significantly change. Ethoxyzolamide induced changes in fluorescence parameters that were more strongly expressed in costata 2/125. The results show that tCA is involved in the regulation of the proton gradient across thylakoid membranes and thus limits PSII downregulation. 相似文献
17.
Bulychev A. A. Cherkashin A. A. Vredenberg W. J. Rubin A. B. Zykov V. S. Müller S. C. 《Russian Journal of Plant Physiology》2001,48(3):326-332
Continuous profiles of local pH near the cell surface of Chara corallinawere recorded during uniform longitudinal movement of an internodal cell relative to a stationary pH microelectrode. Under illumination, the pH profile consisted of alternating acid and alkaline bands with a pH difference of up to 3 pH units. After darkening, the bands disappeared and pH became uniformly distributed along the cell length. Chlorophyll fluorescence of chloroplasts was measured by microfluorometry at different locations within one cell, and significant differences were observed in close relation to light-dependent pH banding. The chlorophyll fluorescence yield was lower in zones of low external pH than in alkaline zones both under actinic and saturating light. The fluorescence parameters Fand F"
m
and the quantum yield of photosystem II (PSII) displayed variations along the cell length in accordance with pH changes in unstirred layers of the medium. The results show that PSII photochemical efficiency and the rate of noncyclic electron transport are higher in the chloroplasts of acid zones (zones of H+extrusion from the cell) than in alkaline zones. The dependence of photosynthetic electron transport on local pH near the cell surface may result from different contents of CO2in acid and alkaline regions. The acid zones are enriched with CO2that readily permeates through the membrane providing the substrate for the Calvin cycle. Conversely, a poorly permeating form, HCO–
3is predominant in alkaline zones, which may restrict the dark reactions and photosynthetic electron flow. 相似文献
18.
Chemeris Yu. K. Korol'kov N. S. Seifullina N. Kh. Rubin A. B. 《Russian Journal of Plant Physiology》2004,51(4):435-441
A prolonged (20 h) dark incubation of Chlorella pyrenoidosa algae at 37°C resulted in a twofold rise of the slowly rising phase (10–15 min), sF
v, in the kinetics of variable chlorophyll fluorescence, F
v (F
v = F
m – F
0) in diuron-treated cells. This effect suggests the accumulation of inactive photosystem II (PSII) complexes with low efficiency of primary quinone acceptor of electron of PSII (QA) reduction. The presence of methylamine (MA), a thylakoid membrane uncoupler, or N, N-dicyclohexylcarbodiimide, an inhibitor of ATPase, precluded the accumulation of inactive PSII complexes. When salicylhydroxamate promoted the reduction of the plastoquinone (PQ) pool, exogenous ATP accelerated the accumulation of inactive complexes. Dark PQ oxidation in the presence of nonmetabolized glucose analog, 2-deoxy-D-glucose, lowered the content of inactive PSII complexes, and NaF, an inhibitor of chloroplast phosphatases, retarded this process. These data are considered as evidence for a mechanism regulating the content of inactive PSII complexes in the process of redox-dependent phosphorylation of D1- and/or D2-proteins of PSII. 相似文献
19.
Semin BK Davletshina LN Bulychev AA Ivanov II Seibert M Rubin AB 《Biochemistry. Biokhimii?a》2007,72(11):1205-1215
20.
The usefulness of 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS) for in-situ studies of the chloroplast phosphate translocator was evaluated by fluorescence microscopy and radiolabeling of spinach (Spinacia oleracea L.) (C3 plant) and maize (Zea mays L.) (C4 plant) chloroplasts. In maize mesophyll and bundle-sheath chloroplasts and in spinach chloroplasts that were either intact, broken or swollen, DIDS fluorescence was only associated with the chloroplast envelope. Intact chloroplasts often had fluorescent patches corresponding to concave regions of the chloroplast which we assume to be regions enriched in DIDS-binding sites.Incubation of intact or broken spinach chloroplasts or maize mesophyll chloroplasts with [3H2]DIDS resulted in the labeling of a single polypeptide (relative molecular mass, Mr, 30 kDa) in the envelope fraction, in each case. Label in the stromal fraction was not detected when intact chloroplasts were incubated with [3H2]DIDS. However, when broken chloroplasts were incubated with [3H2]DIDS, several polypeptides of various molecular masses were labeled, but not the 30×31-kDa polypeptide. In thylakoid fractions from both broken and intact chloroplasts, a single 30×31-kDa polypeptide was labeled inconsistently. When a mixture of intact maize mesophyll and bundle-sheath chloroplasts was labeled with [3H2]DIDS, extracts of whole chloroplasts displayed radioactivity only in the 30×31-kDa band.We conclude that DIDS is a valuable probe for the in-situ identification and characterization of the 30-kDa protein — the presumptive phosphate translocator — in C3 and C4 chloroplasts since DIDS (1) does not penetrate the inner membrane of the envelope of intact chloroplasts and, therefore, (2) does not bind internal sites in intact chloroplasts, and (3) only binds the 30-kDa protein in the inner membrane of the envelope.Abbreviations CBB
Coomassie brilliant blue
- DIC
differential interference contrast optics
- DIDS
4,4-diisothiocyanatostilbene-2,2-disulfonic acid
- [3H2]DIDS
1,2-ditritio-1,2-(2,2-disulfo-4,4-diisothiocyano)diphenylethane
- kDa
kilodalton
- Mr
relative molecular mass
- PGA
3-phosphoglycerate
- Pitranslocator
phosphate translocator
- SDS
sodium dodecyl sulfate 相似文献