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1.
O. Misumi L. Suzuki Y. Nishimura A. Sakai S. Kawano H. Kuroiwa T. Kuroiwa 《Protoplasma》1999,209(3-4):273-282
Summary Each wild-typeChlamydomonas reinhardtii cell has one large chloroplast containing several nuclei (nucleoids). We used DNA insertional mutagenesis to isolate Chlamydomonas mutants which contain a single, large chloroplast (cp) nucleus and which we namedmoc (monokaryotic chloroplast). DAPI-fluorescence microscopy and microphotometry observations revealed thatmoc mutant cells only contain one cp-nucleus throughout the cell division cycle, and that unequal segregation of cpDNA occurred during cell division in themoc mutant. One cell with a large amount of cpDNA and another with a small amount of cpDNA were produced after the first cell division. Unequal segregation also occurred in the second cell division, producing one cell with a large amount (about 70 copies) of cpDNA and three other cells with a small amount (only 2–8 copies) of cpDNA. However, most individualmoc cells contained several dozen cpDNA copies 12 h after the completion of cell division, suggesting that cpDNA synthesis was activated immediately after chloroplast division. In contrast to the cpDNA, the mitochondrial (mt) DNA of themoc mutants was observed as tiny granules scattered throughout the entire cell. These segregated to each daughter cell equally during cell division. Electron-microscopic observation of the ultrastructure ofmoc mutants showed that a low-electron-density area, which was identified as the cp-nucleus by immunoelectron microscopy with anti-DNA antibody, existed near the pyrenoid. However, there were no other structural differences between the chloroplasts of wild-type cells andmoc mutants. The thylakoid membranes and pyrenoid were identical. Therefore, we propose that the novelmoc mutants are only defective in the dispersion and segregation of cpDNA. This strain should be useful to elucidate the mechanism for the segregation of cpDNA.Abbreviations DAPI
4,6-diamidino-2-phenylindole
- VIMPCS
video-intensified microscope photon-counting system 相似文献
2.
Juliana A. Fernando Maria Lúcia C. Vieira Silvia R. Machado Beatriz Appezzato-da-Glória 《Plant Cell, Tissue and Organ Culture》2007,91(1):37-44
We present evidences that ultrastructural electron microscope findings are valuable ways to understand the in vitro regeneration
process, in particular in the yellow passion fruit. Shoot-regeneration was induced in hypocotyl and leaf-derived explants
using 4.44 μM BAP, and the entire organogenic process was analyzed using conventional histology, scanning and transmission
electronic microscopy. Both direct and indirect regeneration modes were observed in hypocotyl explants, but only direct regeneration
occurred in leaf-derived cultures. In the direct pathway from both explant types, meristemoids developed into globular structures,
here called protuberances. The peripheral meristematic layers of the protuberances displayed ultrastructural characteristics
indicative of a high metabolic activity, and only these cells originated shoots and leaf primordia, the latter being frequent
when leaf explants were used. Moreover, the peripheral cells of the protuberances derived from leaf explants lost adhesion
during the culture, diminishing the regeneration rates. We recommend the use of hypocotyls as a source of explant to obtain
shoots as well as a genetic transformation system for the yellow passion fruit. However, the direct pathway is preferred because
a type of amitosis occurred in the peripheral cells of hypocotyl-derived calli, which has the potential to result in genetic
instability of the regenerating plants/tissue. 相似文献
3.
NaCl-induced changes in the thylakoid membrane of wild-type Anabaena variabilis and its NaClr mutant strain have been studied. Biochemical characterization of the thylakoid membrane was done by taking its absorption
and fluorescence spectra at different wavelength. The thylakoid membranes of both strains were isolated by mechanical disruption
of the freeze-dried and lysozyme-treated cells, followed by differential and density gradient centrifugation. The light absorption
spectra of the thylakoid membrane showed three and two peaks in NaClr mutant strain and its wild-type counterpart respectively at wavelengths of 400–850 nm. These peaks revealed that the thylakoid
membrane contains a large amount of carotenoid and chlorophyll a. Fluorescence emission spectra of thylakoid membrane of NaClr mutant and its wild-type strain at excitation wavelength of 335 nm showed two different peaks, one at 340 nm and the other
at 663 nm respectively. The light absorption and fluorescence spectra of the thylakoid membrane also revealed that the membrane
contained carotenoid pigment, chlorophyll (Chl) a, and a pigment with an emission peak at 335 nm. The HPLC analysis of the pigments of the thylakoid membrane indicates that
the NaClr mutant strain under NaCl stress contained an additional peak for the carotenoid pigment, which was lacking in its wild-type
counterpart. The major peak in thylakoid membrane was that of echinenone and β-carotene. Whereas the polypeptide composition
of thylakoid membrane differed in the wild-type and its NaClr mutant strain, no difference in the cell wall protein pattern was observed in both strains. The thylakoid membrane of NaClr mutant strain contained two additional protein bands that were absent in its wild-type counterpart. The thylakoid membrane
of the wild-type and its NaClr mutant strain also showed morphological variations under NaCl stress.
Received: 14 April 2000 / Accepted: 23 May 2000 相似文献
4.
In our previous work we found considerable accumulation of early light-inducible proteins (ELIPs) in barley during adaptation
to combined high light and cold stress, an accumulation which occurred preferentially in the apical part of the leaves (M.-H.
Montané et al., 1997, Planta 202: 293–302). Here we studied, under the same conditions, the effect of adaptation on the composition
of thylakoid membrane proteins and pigments, particularly xanthophylls and chlorophyll, and their distribution within the
barley leaf. It was observed that high light fluxes appeared to favour the trimerization of the light-harvesting complex of
photosystem II (LHC II) whereas cold appeared to favour the monomers of LHC II. High light, cold or the combination of both
factors had only a small effect on the protein composition of the thylakoid membranes except for the proteins of LHC II which
were found to decrease under high light to a greater extent at 25 °C than at 5 °C. The total xanthophyll-cycle carotenoid
content increased linearly with cellular development, the highest amount being observed in the apical part of the leaf. Cold
and high light acted synergistically to induce less than a doubling in the amount of total xanthophylls, while chlorophylls
a and b remained nearly constant. The fraction consisting of antheraxanthin plus zeaxanthin was up to 4- to 5-fold higher at 5 °C
than at 25 °C. As determined previously (Montané et al. 1997), the same conditions caused a 15-fold increase in the accumulation
of ELIPs. Consequently, neither the distribution of total xanthophylls nor that of antheraxanthin plus zeaxanthin along the
leaf followed the same pattern as ELIP. Thus, the accumulation of xanthophylls cannot be stoichiometrically correlated with
that of ELIPs. Using electrophoresis in the presence of decylmaltoside, we could demonstrate for the first time that ELIPs
of 13.5 kDa are contained in high-molecular-mass complexes of >100 kDa, which are located in the unstacked stroma lamellar
region of the thylakoid membranes.
Received: 6 April 1998 / Accepted: 26 January 1999 相似文献
5.
By means of circular dichroism (CD) spectroscopy, we have characterized the organization of the photosynthetic complexes of
the diatom Phaeodactylum tricornutum at different levels of structural complexity: in intact cells, isolated thylakoid membranes and purified fucoxanthin chlorophyll
protein (FCP) complexes. We found that the CD spectrum of whole cells was dominated by a large band at (+)698 nm, accompanied
by a long tail from differential scattering, features typical for psi-type (polymerization or salt-induced) CD. The CD spectrum
additionally contained intense (−)679 nm, (+)445 nm and (−)470 nm bands, which were also present in isolated thylakoid membranes
and FCPs. While the latter two bands were evidently produced by excitonic interactions, the nature of the (−)679 nm band remained
unclear. Electrochromic absorbance changes also revealed the existence of a CD-silent long-wavelength (∼545 nm) absorbing
fucoxanthin molecule with very high sensitivity to the transmembrane electrical field. In intact cells the main CD band at
(+)698 nm appeared to be associated with the multilamellar organization of the thylakoid membranes. It was sensitive to the
osmotic pressure and was selectively diminished at elevated temperatures and was capable of undergoing light-induced reversible
changes. In isolated thylakoid membranes, the psi-type CD band, which was lost during the isolation procedure, could be partially
restored by addition of Mg-ions, along with the maximum quantum yield and the non-photochemical quenching of singlet excited
chlorophyll a, measured by fluorescence transients. 相似文献
6.
The cytological sequence of senescence-related changes in coleoptiles of rice (Oryza sativa L. cv. Nippon-bare) was studied using fluorescence and electron microscopy. The coleoptiles reach full size 3 d after sowing,
then rapidly senesce and wither completely by day 7. The interveinal region in cross-sections taken 1 mm from the tip of the
coleoptile was selected for this analysis. Fluorescence microscopy using samples embedded in Technovit 7100 resin, electron
microscopy and immunoelectron microscopy using DNA-specific antibodies were used to elucidate the sequence of senescence-related
events. These occur in the following order: (i) degradation of the chloroplast DNA (cpDNA); (ii) condensation of the nucleus
in conjunction with a decrease in the size of the dense-chromatin region, shrinkage of the chloroplast, degradation of ribulose-1,
5-bisphosphate carboxylase/oxygenase, dilation of the thylakoid membranes, increase in size and number of osmiophilic globules,
condensation of the cytoplasm; (iii) disorganization of the nucleus, degeneration of the tonoplast; (iv) complete loss of
the cytoplasmic components, distortion of the cell wall, invasion of microorganisms into the intercellular spaces and ultimately
into the cell itself. The mitochondria maintain their ultrastructural integrity and a constant level of mitochondrial DNA
throughout senescence. In young mesophyll cells, invagination of the tonoplast into the vacuole frequently occurs. This occasionally
includes cytoplasmic material, which is digested in the vacuole as senescence proceeds. Immunoelectron microscopy suggests
that cpDNA degradation involves rough digestion first, rather than rapid, direct decomposition of the DNA into nucleotides.
The fragmented cpDNA is then dispersed throughout the chloroplast and cytoplasm.
Received: 9 April 1998 / Accepted: 11 June 1998 相似文献
7.
Elena Zak Anna Sokolenko Günter Unterholzner Lothar Altschmied Reinhold G. Herrmann 《Planta》1997,201(3):334-341
Four distinct integration/translocation routes into/across thylakoid membranes have recently been deduced for nuclear-encoded
polypeptides of the photosynthetic membrane. Corresponding information for the plastid-encoded protein complement is lacking.
We have investigated this aspect with in-organello assays employing chimeric constructs generated with codon-correct cassettes
for genes of plastid-encoded thylakoid proteins, and appropriate transit peptides from six nuclear genes, representing three
targeting classes, as a strategy. The three major plastid-encoded components of the cytochrome b
6
f complex, namely pre-apocytochrome f, (including apocytochrome f, and pre-apocytochrome f lacking the C-terminal transmembrane segment), cytochrome b
6
, and subunit IV, which differ in the number of their transmembrane segments, were studied. Import into chloroplasts could
be observed in all instances but with relatively low efficiency. Thylakoid integration can occurr post-translationally, but
only components with secretory/secretory pathway (SEC)-route-specific epitopes were correctly assembled with the cytochrome
complex, or competed with this process. Inhibitor studies were consistent with these findings. Imported cytochrome b
6
and subunit IV operated with uncleaved targeting signals for thylakoid integration. The corresponding determinant for cytochrome
f is its signal peptide; its C-terminal hydrophobic segment did not, or did not appreciably, contribute to this process. The
N-termini of cytochrome b
6
and subunit IV appear to reside on the same (lumenal) side of the membrane, consistent with the currently favored four-helix
model for the cytochrome, but in disagreement with the topography proposed for both components. The impact of the findings
for protein routing, including for applied approaches such as compartment-alien transformation, is discussed.
Received: 18 September 1996 / Accepted: 15 October 1996 相似文献
8.
The sea anemoneCereus pedunculatus was artificially UV-irradiated to test the effect of UV-light on the number of endosymbiotic dinoflagellates in its gastrodermis
and on their ultrastructure. Anemones were kept in the laboratory in a light: dark cycle (LD 12∶12; 13 W m−2) at 18 °C and briefly (2, 5 and 9 d) exposed to UV radiation at quasisolar intensities, 0.5 or 1 W m−2. Their tentacles were then examined in the electron microscope for qualitative and quantitative changes in the zooxanthellae.
There was an intensity-dependent decrease in the number of symbionts, which in some cases were lost altogether (bleaching).
Irradiated anemones contained a larger proportion of symbionts with ultrastructural abnormalities, namely diminished starch,
some mitochondria with altered matrix and, in particular, characteristic changes in the chloroplasts; instead of being densely
stacked, the thylakoids were spread apart and swollen at the ends of their membranes to form vesicle-like structures. Relatively
large vesicles also appeared in the cytoplasm. The resulting enlargement of the whole dinoflagellate cell was documented morphometrically.
Another intensity-dependent effect was a significant decrease in mitosis rate, established by counting dividing symbiont cells
in TEM micrographs. *** DIRECT SUPPORT *** A03B6037 00006 相似文献
9.
Primary production in many ephemeral waters peaks soon after inundation, but the extent to which the algal biomass generated
by this process is immediately available to aquatic herbivores as a food source has not been extensively studied. To examine
this, we exposed natural epilithon from two permanent and two recently rewetted temporary reaches of an intermittent stream
to grazing by small, presumably newly hatched, Limnodynastes tasmaniensis tadpoles and compared the algal content of tadpole feces to that of the assemblages on which they grazed. Rocks from the
temporary sites, one colonized by tadpoles and one not, supported relatively flocculent, diatom-rich (79.7–85.7%) epilithon
of similar biomass and taxonomic content. Epilithon from the permanent sites (one with and one without tadpoles) were more
cohesive, contained fewer diatoms (57.0–60.7%), and differed in species composition from that of the temporary sites, and
from one another. Feces and epilithon were more taxonomically similar when epilithon originated from temporary reaches than
from permanent sites. This implies that grazing tadpoles accessed a greater percentage of the algal assemblages from recently
rewetted sites. Algal species differed in susceptibility to ingestion by small tadpoles, but these differences were not consistent
among habitats; susceptibility to ingestion was not predictable based solely on species growth habit, but was likely also
affected by physiognomic differences in mat structure among habitats. A large percentage of algal cells ingested by tadpoles
survived gut passage. `Live' cells (those with full chloroplasts) comprised 43.8–66.6% of all diatoms from epilithic samples
and 27.4–42.7% of those in feces of small tadpoles. In contrast, only 12.8–14.9% of the diatoms in feces produced by large
L. tasmaniensis tadpoles collected from the two tadpole-colonized sites contained full chloroplasts, suggesting higher digestion efficiency
in large tadpoles than in small ones. Distinct, gut-passage-induced transitions from `live' diatoms to empty frustules or
single diatom valves (`dead' cells) were evident when grazed material originated from temporary reaches. In contrast, `live'
diatoms in epilithon from permanent sites were more likely to emerge in tadpole feces with reduced or fragmented chloroplasts.
Thus, algae from temporary reaches appeared to be more efficiently digested than those from permanent reaches. While digestibility
of individual taxa varied among sites, some algae (e.g., Synedra ulna) were clearly more digestible than others. Our results suggest that temporary stream reaches in arid-zone catchments are
important sources of readily digestible autotrophic biomass for anuran species in these regions.
Received: 5 March 1998 / Accepted: 9 November 1998 相似文献
10.
Priscila L. Grato Carolina C. Monteiro Mnica L. Rossi Adriana P. Martinelli Lzaro E.P. Peres Leonardo O. Medici Peter J. Lea Ricardo A. Azevedo 《Environmental and Experimental Botany》2009,67(2):387-394
Cadmium (Cd) is a toxic heavy metal, which can cause severe damage to plant development. The aim of this work was to characterize ultrastructural changes induced by Cd in miniature tomato cultivar Micro-Tom (MT) mutants and their wild-type counterpart. Leaves of diageotropica (dgt) and Never ripe (Nr) tomato hormonal mutants and wild-type MT were analysed by light, scanning and transmission electron microscopy in order to characterize the structural changes caused by the exposure to 1 mM CdCl2. The effect of Cd on leaf ultrastructure was observed most noticeably in the chloroplasts, which exhibited changes in organelle shape and internal organization, of the thylakoid membranes and stroma. Cd caused an increase in the intercellular spaces in Nr leaves, but a decrease in the intercellular spaces in dgt leaves, as well as a decrease in the size of mesophyll cells in the mutants. Roots of the tomato hormonal mutants, when analysed by light microscopy, exhibited alterations in root diameter and disintegration of the epidermis and the external layers of the cortex. A comparative analysis has allowed the identification of specific Cd-induced ultrastructural changes in wild-type tomato, the pattern of which was not always exhibited by the mutants. 相似文献
11.
Klaus-Peter Michel Pablo Exss-Sonne Gabriele Scholten-Beck Uwe Kahmann Hans Georg Ruppel Elfriede K. Pistorius 《Planta》1998,205(1):73-81
Iron-deficiency-induced protein A (IdiA) with a calculated molecular mass of 35 kDa has previously been shown to be essential
under manganese- and iron-limiting conditions in the cyanobacteria Synechococcus PCC 6301 and PCC 7942. Studies of mutants indicated that in the absence of IdiA mainly photosystem II becomes damaged, suggesting
that the major function of IdiA is in Mn and not Fe metabolism (Michel et al. 1996, Microbiology 142: 2635–2645). To further elucidate the function of IdiA, the immunocytochemical localization of IdiA
in the cell was examined. These investigations provided evidence that under mild Fe deficiency IdiA is intracellularly localized
and is mainly associated with the thylakoid membrane in Synechococcus PCC 6301. The protein became distributed throughout the cell under severe Fe limitation when substantial morphological changes
had already occurred. For additional verification of a preferential thylakoid membrane association of IdiA, these investigations
were extended to the thermophilic Synechococcus elongatus. In this cyanobacterium Mn deficiency could be obtained more rapidly than in the mesophilic Synechococcus PCC 6301 and PCC 7942, and the thylakoid membrane structure proved to be more stable under limiting growth conditions. The
immunocytochemical investigations with this cyanobacterium clearly supported a thylakoid membrane association of IdiA. In
addition, evidence was obtained for a localization of IdiA on the cytoplasmic side of the thylakoid membrane. All available
data support a function of IdiA as an Mn-binding protein that facilitates transport of Mn via the thylakoid membrane into
the lumen to provide photosystem II with Mn. A possible explanation for the observation that IdiA was not only expressed under
Mn deficiency but also under Fe deficiency is given in the discussion.
Received: 28 July 1997 / Accepted: 26 November 1997 相似文献
12.
13.
Dunaliella salina V-63 was cultivated in different concentrations of NaCl (0.5, 1.0, 2.5, 3.0, or 4.0 M) and at two irradiances (170 or 220
μmol m−2s−1). Concentration-dependent suppression of growth was observed above 1 M NaCl, and elevated salinity induced formation of salt-containing
vacuoles. However, the changes in the chloroplast ultrastructure following changes in salinity and irradiance (increase of
invaginations and protuberances, numerous grana with low number of thylakoids, less number of starch grains, etc.) appeared to be of primary importance.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The effect of streptomycin on morphogenic explants of Lycopersicon peruvianum Mill. was examined microscopically at both the light and ultrastructural level. Early stages in shoot regeneration from leaf explants were distinguished as meristematic tissue at both levels. Small starch grains were observed in the plastids in this tissue but not in plastids in regenerated shoots. In the presence of streptomycin, adventitious shoot regeneration from sensitive leaf strips was inhibited. Large layered bodies were observed within the plastids of sensitive leaf tissue, suggesting the disruption of thylakoid membrane formation. Streptomycin resistant L. peruvianum lines, as well as a chlorophyll-deficient line, were also examined microscopically. The chloroplasts of newly regenerated streptomycin resistant shoots contained well developed internal membranes and conspicuous starch grains. Cells containing a mixture of resistant and sensitive plastids were not observed. The plastids in chlorophyll-deficient tissue completely lacked thylakoid membranes, although small vesicles and intraplastid bodies were seen within the stroma.Abbreviations NMU
N-methyl-N-nitrosourea 相似文献
15.
M. Pillay C. Mazzella 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,95(4):696-701
Chloroplast DNA (cpDNA) of Paspalum dilatatum and P. notatum was digested singly or in combination with the restriction endonucleases PstI, PvuII, SalI, KpnI and XhoI. Data obtained from filter hybridization experiments with barley and wheat cpDNA probes were used to construct restriction
site maps of the chloroplast genomes of the Paspalum species. The cpDNA fragments were ordered into a circular configuration of approximately 139.3 kbp that contained two inverted
repeat regions of approximately 23 kbp and a small and large single-copy region of approximately 11 kbp and 83 kbp, respectively.
The cpDNA maps showed that P. dilatatum and P. notatum shared a large number of restriction sites with the proportion of shared restriction sites S=0.90. No restriction site differences
were detected in the KpnI maps. Eight species-specific restriction site differences that could be used to identify the cytoplasm of each Paspalum species were identified in the PstI, PvuII, SalI, and XhoI cleavage maps. The overall structural organization of the Paspalum cpDNAs is rather similar to those of most cpDNAs from other plants. The results presented in this study will be of value
for exploring further phylogenetic relationships within the genus Paspalum.
Received: 27 February 1997 / Accepted: 7 March 1997 相似文献
16.
High diversity of <Emphasis Type="Italic">Ruppia</Emphasis> meadows in saline ponds and lakes of the western Mediterranean 总被引:1,自引:1,他引:0
Saline inland and coastal waterbodies are valuable habitats that deserve attention for the protection of their unique submerged
macrophyte beds that render the water clear, stabilize sediments and provide a habitat for high biomasses of invertebrates
as food for waterfowl. The ‘continental seagrass’ Ruppia has the widest salinity tolerance among the submerged macrophytes and occurs in a wide variety of saline saltmarsh pond and
lagoon systems. Although two cosmopolitan species Ruppia maritima and Ruppia cirrhosa are recognized in Europe and Ruppia drepanensis in the western Mediterranean, their diversity and distribution are not well known. This previously held traditional idea
that there are only two widespread Ruppia species suggests a uniform and very homogenized population structure following the hypothesis of long-distance-dispersal
through strong bird-mediated dispersal events. Therefore, the Ruppia chloroplast DNA diversity was investigated along a more than 1,000 km transect of the Iberian Peninsula. We studied 492 individuals
from 11 wetland areas (17 ponds) and sequenced a 1,753-bp length of seven chloroplast introns. Eight haplotypes represented
at least four distinct groups or taxa which is higher than commonly accepted. Six wetland areas contained more than one haplotype
and within-pond diversity occurred within distances as small as 30 m (5 out of 17 cases). This underlines the importance of
single waterbodies for harbouring haplotypic diversity in Ruppia. Unique haplotypes were observed in four wetland areas and R. maritima was detected only from a low salinity pond, suggesting the species might be more rare than previously accepted. The present
results tend to minimize an overall effect of strong bird-mediated dispersal. This emphasizes the role of regional pond habitat
diversity for the preservation of Ruppia taxa and their unique haplotype diversity in extreme saline habitats.
Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle
Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16
May 2008. 相似文献
17.
Chlamydomonas is an unicellular green alga that contains one cup-shaped chloroplast with about 60 copies of cpDNA. Chloroplasts (cp) multiply
in the cytoplasm of the plant cell by binary division, with multiple copies of cpDNA transmitted and maintained in successive
generations. The effect of cpDNA copy number on cell proliferation and aging was investigated using a C. reinhardtii moc mutant, which has an undispersed cp-nucleoid and unequal segregation of cpDNA during cell division. When the mother cell
divided into four daughters, one moc daughter cell chloroplast contained about 60 copies of cpDNA, and the chloroplasts in the three other daughter cells contained
the 4–7 copies of cpDNA. In liquid medium, the number of moc cells at the period of stationary phase was about one-third that of the wild type. To observe the process of proliferation
and aging in the mother cell, we used solid medium. Three out of four moc cell spores were preferentially degenerated 60 days after cell transfer. To confirm this, wild-type and moc mother cells containing four daughter cells were treated with novobiocin to inhibit cpDNA replication. Cell degeneration
increased only in the moc strain following novobiocin introduction. In total, our results suggest that cells possessing smaller amounts of cpDNA degenerate
and age more rapidly.
Received 7 September 2000/ Accepted in revised form 14 February 2001 相似文献
18.
Severe chlorosis and ultrastructural modifications of chloroplasts occur in sunflower in response to infection by Pseudomonas syringae pv. tagetis. Chlorosis became apparent within 2 days after the cotyledons of 10-day-old sunflower seedlings were inoculated with the bacteria. The first symptoms generally appeared in the center of leaves at the second node above the cotyledons. Leaves above the second node lost essentially all of their pigmentation but remained turgid and continued to expand. Grana thylakoids became dilated and separated from the granal stacks. These thylakoid membranes did not chemically breakdown as in the case in chromoplast formation or normal chloroplast senescence. Both grana and stroma thylakoid membranes coalesced to form a large membrane sheet within the plastid. The ultrastructural changes are unlike those reported to be caused by other chlorosis-inducing bacteria or chlorosis associated with normal senescence. 相似文献
19.
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
20.
Ultraviolet-B (UV-B) radiation to thylakoid membrane and fatty acid profile has been investigated in cyanobacterium, Spirulina platensis. The thylakoid membrane was isolated by mechanical disruption of the freeze-dried and lysozyme-treated cells followed by
differential density gradient centrifugation and morphological variations were examined. UV radiation distorted the membrane
on the outer side with reduced chlorophyll a (chl a) content compared to its untreated counterpart. Liquid chromatography-mass
spectrometry (LC-MS) was used for characterization of chl a of the thylakoid membrane. UV-B exposure resulted in alterations
in the pigment-protein complexes 47 kDa and 43 kDa. Furthermore, 94 kDa and 20 kDa protein appeared in UV-B-exposed thylakoid
membrane of S. platensis. The composition of fatty acid in response to UV-B radiation was detected by gas chromatography–mass spectrometry having
23.5% saturated fatty acid (SFA), 76.4% monounsaturated fatty acid (MUFA), and polyunsaturated fatty acid (PUFA). In contrast
to its UV-B-untreated counterpart, SFA was 46.6%, and MUFA and PUFA were 53.3%. Our findings suggest that UV-B radiation not
only affects membrane morphology and its protein profile but also reduces saturated fatty acid and increases unsaturated fatty
acids in S. platensis. 相似文献