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1.
Summary. 10 nm diameter filaments were observed in whole-mount preparations of algae of diverse phyla: Acetabularia acetabulum and A. major (Chlorophyta), Chara australis and Nitella flexilis (Charophyta), and Poterioochromonas malhamensis (Chrysophyta). A polyclonal antibody raised against a basic, 50 kDa DNA-binding protein of A. acetabulum stains the filaments of A. acetabulum and A. major as well as of C. australis and N. flexilis. While in the perinuclear region of A. acetabulum and A. major and throughout the cytoplasm of P. malhamensis the 10 nm filaments have a smooth appearance, in the stalk of A. acetabulum and A. major they are densely covered by globular structures; in C. australis and N. flexilis they are less frequently associated with such material. The morphology of a part of the globular particles is quite reminiscent
of prosomes. A monoclonal antibody elicited against prosomes isolated from A. acetabulum indeed decorates the globular particles on the A. acetabulum and A. major filaments. The possible role of these filament-particle associations is discussed.
Received August 10, 2001; accepted October 30, 2002; published online April 8, 2003
RID="*"
ID="*" Correspondence and reprints: Max-Planck-Institut für Zellbiologie, 68526 Ladenburg, Federal Republic of Germany. E-mail:
sberger@zellbio.mpg.de
RID="**"
ID="**" Present address: Long Island University, Southampton, New York, U.S.A.
RID="+"
ID="+" Present address: Leica Microsystems Wetzlar GmbH, Wetzlar, Federal Republic of Germany 相似文献
2.
3.
We establish the existence of traveling front solutions and small amplitude traveling wave train solutions for a reaction-diffusion
system based on a predator-prey model with Holling type-II functional response. The traveling front solutions are equivalent
to heteroclinic orbits in R
4
and the small amplitude traveling wave train solutions are equivalent to small amplitude periodic orbits in R
4
. The methods used to prove the results are the shooting argument and the Hopf bifurcation theorem.
Received: 25 May 2001 / Revised version: 5 August 2002 / Published online: 19 November 2002
RID="*"
ID="*" Research was supported by the National Natural Science Foundations (NNSF) of China.
RID="*"
ID="*" Research was partially supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada. On leave
from the Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 3J5, Canada.
Mathematics Subject Classification (2000): 34C35, 35K57
Key words or phrases: Traveling wave solution – Wazewski set – Shooting argument – Hopf bifurcation
Acknowledgements. We would like to thank the two referees for their careful reading and helpful comments. 相似文献
4.
Summary. Sphingomyelin is an abundant constituent of the plasma membranes of mammalian cells. Ceramide, its primary catabolic intermediate,
has emerged as an important lipid signaling molecule. Previous work carried out by our group has documented that plasma membrane
Mg2+-dependent neutral sphingomyelinase can be effectively inhibited by exogenous ubiquinol. In this work, we have tested whether
or not plasma-membrane-associated electron transport can also achieve this inhibition through endogenous ubiquinol. Our results
have shown that Mg2+-dependent neutral sphingomyelinase in isolated plasma membranes was inhibited by NAD(P)H under conditions where ubiquinone
is reduced to ubiquinol. This inhibition was potentiated in the presence of an extra amount of NAD(P)H:(quinone acceptor)
oxidoreductase 1 (EC 1.6.99.2). Depletion of plasma membranes from lipophilic antioxidants by solvent extraction abolished
the inhibition by reduced pyridine nucleotides without affecting the sensitivity of the neutral sphingomyelinase to exogenous
ubiquinol. Reconstitution of plasma membranes with ubiquinone restored the ability of NAD(P)H to inhibit the enzyme. Our results
support that the reduction of endogenous ubiquinone to ubiquinol by NAD(P)H-driven electron transport may regulate the activity
of the plasma membrane neutral sphingomyelinase.
Received May 20, 2002; accepted September 20, 2002; published online May 21, 2003
RID="**"
ID="**" Present address: Department of Biomedical Engineering, School of Medicine, University of Baltimore, Maryland, U.S.A.
RID="*"
ID="*" Correspondence and reprints: Departamento de Biología Celular, Fisiología e Inmunología, Facultad de Ciencias, Edificio
C-6, Campus Rabanales, Universidad de Córdoba, 14014 Córdoba, Spain. 相似文献
5.
A novel mechanism of silicon uptake 总被引:4,自引:0,他引:4
Summary. Crystal-like structures in vacuoles, precipitates in the cytoplasm and on the tonoplast membrane have been found to store
remarkable amounts of Si in a number of higher plants. In most of the cases the final storage product is a SiO2 gel. Accumulation inside the cells presumes a membrane and cytoplasm passage, driven by unknown transporters. Beside this
uptake into the cytoplasm, Si-accumulating species possess a mechanism that does not involve a membrane and cytoplasm passage.
Unusual small invaginations comprising the two membranes, plasmalemma and tonoplast, which enclose a small border of cytoplasm,
were observed. The same cells contained vacuolar vesicles surrounded by two membranes, obviously derived from the invaginations.
By energy-dispersive X-ray analysis and electron spectroscopic imaging, Si was shown in the invaginations and vacuolar vesicles.
This novel endocytotic process allows the uptake of condensed, higher-molecular-weight Si compounds. In Zn hyperaccumulators,
frequently SiO2 precipitates were found in different cell compartments. Such plants showed the same invaginations and vacuolar vesicles,
but Zn, colocalized with Si, was detected in these structures. Electron energy loss spectra confirmed the assumption that
Zn-silicate is present in the vesicles. In the vacuoles the unstable Zn-silicate is degraded, forming SiO2 precipitates, while the released Zn is bound to an unknown partner.
Received January 22, 2002; accepted July 2, 2002; published online October 31, 2002
RID="*"
ID="*" Correspondence and reprints: Institute of Plant Biochemistry, Weinberg 3, 06120 Halle, Federal Republic of Germany.
Abbreviations: EELS electron energy loss spectroscopy; EDX energy-dispersive analysis of X-rays; ESI electron spectroscopic imaging. 相似文献
6.
Summary. The non-Mendelian inheritance of organelle DNA is common in most plants and animals. Here we examined inheritance mechanisms
involved in the transfer of mitochondrial DNA. We successively backcrossed (to F5) two interfertile strains of the unicellular isogamous haploid algae Chlamydomonas reinhardtii and Chlamydomonas smithii to match nuclear backgrounds and examine transmission patterns of mitochondrial DNA by PCR analysis of cob gene sequences. Mitochondrial DNA was strictly transmitted paternally. To investigate the behavior of parental mitochondrial
DNA, we used F5 progeny to form zygotes and isolated single zygotes. The results showed selective disappearance of maternal mitochondrial
nucleoids occurred between 3 and 6 h after zygote formation.
Received July 11, 2002; accepted September 28, 2002; published online June 13, 2003
RID="*"
ID="*" Correspondence and reprints: Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus,
Nishihara, Okinawa 903-0213, Japan. 相似文献
7.
Summary. The 14-residue peptaibol antibiotic trichovirin I 4A of the structure Ac-Aib-L-Asn-L-Leu-Aib-L-Pro-L-Ala-L-Val-Aib-L-Pro-Aib-L-Leu-Aib-L-Pro-L-Leuol
(Aib = α-aminoisobutyric acid, Leuol = leucinol) was synthesized by stepwise conventional solution phase synthesis using the Z/OtBu(OMe) strategy and HOBt/EDC as coupling reagents. Intermediates were fully characterized and the identity of the synthetic
peptide with the component 4A of the natural, microheterogeneous peptide mixture was proven by electrospray mass spectrometry,
HPLC, and bioassay.
Received March 25, 2002 Accepted June 14, 2002 Published online December 18, 2002
RID="*"
ID="*" Dedicated to Prof. Dr. Günther Jung. Tübingen University, on the occasion of his 65th anniversary.
Authors' address: Prof. Dr. Hans Brückner, Interdisciplinary Research Center, Institute of Nutritional Science, Department of Food Sciences,
Justus-Liebig-University of Giessen, Heinrich-Buff-Ring 26, D-35392 Giessen, Germany, Fax: +49-641-99-39149, E-mail: hans.brueckner@ernaehrung.uni-giessen.de
Abbreviations: Amino acids are abbreviated according to three-letter-nomenclature; Aib, α-aminoisobutyric acid (2-methylalanine); Iva (isovaline, 2-ethylalanine); Leuol, L-leucinol [(S)-2-amino-4-methyl-1-pentanol]; AAA, amino acid analysis; EI-MS, electron impact mass spectrometry; ESI-MS, electrospray ionization
mass spectrometry; HPLC, high performance liquid chromatography; Z, benzyloxycarbonyl; Fmoc, 9-fluorenylmethyoxycarbonyl;
OtBu, tertiary butoxy (tert-butylester); OMe, methoxy (methyl ester); OBzl, benzyloxy (benzyl ester); TDM, N,N,N′,N′-tetramethyl-4,4′-diamino-diphenylmethane
(Arnold's base); for other abbreviations see Experimental. 相似文献
8.
We introduce inhomogeneous, substrate dependent cell division in a time discrete, nonlinear matrix model of size-structured
population growth in the chemostat, first introduced by Gage et al. [8] and later analysed by Smith [13]. We show that mass conservation is verified, and conclude that our system admits one
non zero globally stable equilibrium, which we express explicitly. Then we run numerical simulations of the system, and compare
the predictions of the model to data related to phytoplankton growth, whose obtention we discuss. We end with the identification
of several parameters of the system.
Received: 9 February 2000 / Revised version: 10 October 2001 / Published online: 23 August 2002
RID="*"
ID="*" Present address: Department of Mathematics and Statistics, University of Victoria, B.C., Canada. e-mail: jarino@math.uvic.ca
Key words or phrases: Chemostat – Structured population models – Discrete model – Inhomogeneous division size 相似文献
9.
Yoshie Matsuda Genqing Liang Yali Zhu Fengshan Ma Richard S. Nelson Biao Ding 《Protoplasma》2002,220(1-2):0051-0058
Summary. Previous work has demonstrated that some endogenous plant gene promoters are active in selective companion cells of the phloem,
depending on organ types and developmental stages. Here we report that the Commelina yellow mottle virus (CoYMV) promoter
is active in the companion cells of leaves, stems and roots of transgenic Nicotiana tabacum cv. Xanthi NN, using β-glucuronidase (GUS) as a reporter. Thus, the CoYMV promoter has a broad organ specificity. This promoter
can be useful in molecular studies on the functions of companion cells in many aspects of phloem biology, such as regulation
of long-distance transport, macromolecular traffic, plant development and interaction with pathogens. It may also be useful
in engineering crops that produce specific gene products in the companion cells to block long-distance movement of pathogens.
Received February 5, 2002; accepted March 27, 2002; published online July 4, 2002
RID="*"
ID="*" Correspondence and reprints: Department of Plant Biology and Plant Biotechnology Center, 207 Rightmire Hall, Ohio State
University, 1060 Carmack Road, Columbus, OH 43210, U.S.A. 相似文献
10.
Differential localisation of GFP fusions to cytoskeleton-binding proteins in animal, plant, and yeast cells 总被引:3,自引:0,他引:3
Summary. The structure and functioning of the cytoskeleton is controlled and regulated by cytoskeleton-associated proteins. Fused
to the green-fluorescent protein (GFP), these proteins can be used as tools to monitor changes in the organisation of the
cytoskeleton in living cells and tissues in different organisms. Since the localisation of a specific cytoskeleton protein
may indicate a particular function for the associated cytoskeletal element, studies of cytoskeleton-binding proteins fused
to GFP may provide insight into the organisation and functioning of the cytoskeleton. In this article, we focused on two animal
proteins, human T-plastin and bovine tau, and studied the distribution of their respective GFP fusions in animal COS cells,
plant epidermal cells (Allium cepa), and yeast cells (Saccharomyces cerevisiae). Plastin-GFP localised preferentially to membrane ruffles, lamellipodia and focal adhesion points in COS cells, to the actin
filament cytoskeleton within cytoplasmic strands in onion epidermal cells, and to cortical actin patches in yeast cells. Thus,
in these 3 very different types of cells plastin-GFP associated with mobile structures in which there are high rates of actin
turnover. Chemical fixation was found to drastically alter the distribution of plastin-GFP. Tau-GFP bound to microtubules
in COS cells and onion epidermal cells but failed to bind to yeast microtubules. Thus, animal and plant microtubules appear
to have a common tau binding site which is absent in yeast. We conclude that the study of the distribution patterns of microtubule-
and actin-filament-binding proteins fused to GFP in heterologous systems should be a valuable tool in furthering our knowledge
about cytoskeleton function in eukaryotic cells.
Received January 12, 2002; accepted March 7, 2002; published online June 24, 2002
RID="*"
ID="*" Correspondence and reprints (present address): Institute of Botany, University of Bonn, Kirschallee 1, 53115 Bonn,
Federal Republic of Germany.
Abbreviation: smRS-GFP soluble modified red-shifted GFP. 相似文献
11.
Summary. Wheat (Triticum aestivum L.) roots released proteins showing peroxidase activity in the apoplastic solution in response to wound stress. Preincubation
of excised roots with 1 mM salicylic acid at pH 7.0 enhanced the guaiacol peroxidase activity of the extracellular solution
(so-called extracellular peroxidase). The soluble enzymes were partially purified by precipitation with ammonium sulfate followed
by size exclusion and ion exchange chromatography. Despite an increase in the total activity of secreted peroxidase induced
by pretreatment of excised roots with salicylic acid, the specific activity of the partially purified protein was significantly
lower compared to that of the control. Purification of the corresponding proteins by ion exchange chromatography indicates
that several isoforms of peroxidase occurred in both control and salicylic acid-treated samples. The activities of the extracellular
peroxidases secreted by the salicylic acid-treated roots responded differently to calcium and lectins compared with those
from untreated roots. Taken together, our data suggest that salicylic acid changes the isoforms of peroxidase secreted by
wounded wheat roots.
Received June 10, 2002; accepted September 24, 2002; published online May 21, 2003
RID="*"
ID="*" Correspondence and reprints: Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan
420111, Russia. 相似文献
12.
Copper-mediated oxidative burst in Nicotiana tabacum L. cv. Bright Yellow 2 cell suspension cultures
Summary. In cell suspension cultures of Nicotiana tabacum L. cv. Bright Yellow 2 (BY-2) a rapid and concentration-dependent accumulation of H2O2 is induced by excess concentrations of copper (up to 100 μM). This specific and early response towards copper stress was
shown to be extracellular. Addition of 300 U of catalase per ml decreased the level of H2O2. Superoxide dismutase (5 U/ml) induced an increase in H2O2 production by 22.2%. This indicates that at least part of the H2O2 is produced by dismutation of superoxide. Pretreatment of the cell cultures with the NAD(P)H oxidase inhibitors diphenylene
iodonium (2 and 10 μM) and quinacrine (1 and 5 mM) prevented the generation of H2O2 under copper stress for 90%. The influence of the pH on the H2O2 production revealed the possible involvement of cell-wall-dependent peroxidases in the generation of reactive oxygen species
after copper stress.
Received May 20, 2002; accepted July 26, 2002; published online May 21, 2003
RID="*"
ID="*" Correspondence and reprints: Plant Physiology, Department of Biology, University of Antwerp (RUCA), Groenenborgerlaan
171, 2020 Antwerp, Belgium. 相似文献
13.
Summary. This study investigates the relationship between changes in plasma sodium and changes in amino acid levels in a patient with
post-traumatic sepsis and prolonged critical illness. Ninety-two consecutive measurements were performed at regular intervals
over a period of many weeks; these consisted in the determination of full amino-acidograms, plasma sodium and complementary
variables. A unique, highly significant inverse correlation between taurine and plasma sodium was found (r2 = 0.48, p < 0.001). All other amino acids were unrelated, or much more weakly related, to sodium. Taurine was also strongly
and directly related to phosphoethanolamine, glutamate and aspartate. Changes in sodium and in levels of these amino acids
explained up to 86% of the variability of taurine. Besides, levels of these amino acids maintained a high degree of co-variation,
remaining reciprocally related one to each other, directly, with r2 ranging between 0.33 and 0.59 (p < 0.001 for all). There were similar findings for β-alanine, which however was measured inconsistently. These data provide gross clinical evidence of a specific link binding
plasma sodium and taurine levels, and may be consistent with occurrence of opposite and interdependent shifts of sodium and
taurine between intravascular and extravascular space, to maintain osmoregulation. Co-variation of taurine with the other
amino acids may be related to the same phenomenon, and/or to similarities in transport systems and chemical structure, or
true metabolic interactions.
Received April 16, 2002 Accepted June 19, 2002 Published online November 14, 2002
RID="*"
ID="*" Presented at the 7th International Congress on Amino Acids and Proteins, Vienna (Austria), August 6–10, 2001.
Acknowledgements The authors acknowledge the kind assistance of Mr. Maurizio Cianfanelli, from the Catholic University School of Medicine,
Rome, Italy.
Authors' address: Dr. Carlo Chiarla, Via Augusto Tebaldi, 19, I-00168 Roma, Italy, E-mail: carlo.chiarla@rm.unicatt.it 相似文献
14.
Localization of sucrose synthase and callose in freeze-substituted secondary-wall-stage cotton fibers 总被引:2,自引:0,他引:2
Summary. Methods for cryogenic fixation, freeze substitution, and embedding were developed to preserve the cellular structure and
protein localization of secondary-wall-stage cotton (Gossypium hirsutum L.) fibers accurately for the first time. Perturbation by specimen handling was minimized by freezing fibers still attached
to a seed fragment within 2 min after removal of seeds from a boll still attached to the plant. These methods revealed native
ultrastructure, including numerous active Golgi bodies, multivesicular bodies, and proplastids. Immunolocalization in the
context of accurate structure was accomplished after freeze substitution in acetone only. Quantitation of immunolabeling identified
sucrose synthase both near the cortical microtubules and plasma membrane and in a proximal exoplasmic zone about 0.2 μm thick.
Immunolabeling also showed that callose (β-1,3-glucan) was codistributed with sucrose synthase within this exoplasmic zone.
Similar results were obtained from cultured cotton fibers. The distribution of sucrose synthase is consistent with its having
a dual role in cellulose and callose synthesis in secondary-wall-stage cotton fibers.
Received August 19, 2002; accepted November 12, 2002; published online June 13, 2003
RID="*"
ID="*" Correspondence and reprints: Department of Biological Sciences, Texas Tech University, Lubbock, TX 79409-3131, U.S.A.
E-mail: candace.haigler@ttu.edu 相似文献
15.
Branched chain amino acids as source of specific branched chain volatile fatty acids during the fermentation process of fish sauce 总被引:6,自引:0,他引:6
Summary. The source of the formation of branched chain volatile fatty acids (VFA) in fish sauce was investigated. Certain branched
VFA were derived from the degradation of specific amino acids as iso-butyric acid from valine and iso-valeric acid from leucine. Short and long straight chain VFA were significantly higher in the linoleic acid added sample
than in the control but did not significantly bring changes to the branched chain VFA. It is suggested that straight chain
VFA developed from fish fats. Alanine and isoleucine did not have a clear influence on the production of volatile fatty acids.
Received November 23, 2001 Accepted June 20, 2002 Published online December 18, 2002
RID="*"
ID="*" Part of this paper was presented in the 7th International Congress on Amino Acids and Proteins in Vienna, Austria from
August 6–10, 2001.
Authors' address: Norlita G. Sanceda, Ph.D., Institute of Environmental Science for Human Life, 2-1-1 Otsuka, Bunkyo-ku, Tokyo 112, Japan,
Fax: + 81-3-5978-5805, E-mail: lita@cc.ocha.ac.jp 相似文献
16.
Summary. 2H-Pyran-2-ones 1 were transformed with various hydrazines into (E)- or (Z)-α,β-didehydro-α-amino acid (DDAA) derivatives 4 (and 7) containing a highly substituted pyrazolyl moiety attached at the β-position. With heterocyclic hydrazines, the products 4 were accompanied also by decarboxylated enamines E-6. In order to separate (E/Z)-mixtures of acids, they were transformed to the corresponding methyl esters 9 and 10 by the application of diazomethane. Catalytic hydrogenation under high pressures with Pd/C as a catalyst resulted in the formation
of racemic alanine derivatives 11.
Received January 29, 2002 Accepted May 27, 2002 Published online December 18, 2002
RID="*"
ID="*" Dedicated with deep respect to Professor Waldemar Adam on the occasion of his 65th birthday.
Acknowledgements We thank the Ministry of Education, Science and Sport of the Republic of Slovenia for the financial support (P0-0503-103).
Dr. B. Kralj and Dr. D. Žigon (Center for Mass Spectroscopy, “Jožef Stefan” Institute, Ljubljana, Slovenia) are gratefully
acknowledged for the mass measurements.
Authors' address: Prof. Marijan Kočevar, Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana,
Slovenia, E-mail: marijan.kocevar@uni-lj.si 相似文献
17.
Summary. Syagrus coronata is an economically important palm tree grown as an ornament, for the oil extracted from its seeds, and the wax from its leaves
which has several applications in industry. Silicon biocomposites were analyzed in leaves of S. coronata. Silica bodies were found as extracellular silica masses between the hypodermal-layer cell walls and in granules present
in the vacuoles of palisade cells. Scanning electron microscopy of the hypodermal layer of cells showed a collection of spherical
bodies embedded in enveloping cavities that outlined the general structure of the bodies. Globular subunits with sharp edges
formed the spherical bodies that ranged from 6 to 10 μm in diameter (average, 7.8 μm). X-ray microanalysis detected only silicon
and oxygen homogeneously distributed throughout the bodies. Vacuoles of palisade cells contained a large number of granules
ranging from 20 nm to 1.2 μm in size (average, 300 nm). Transmission electron microscopy associated with electron spectroscopic
imaging and electron energy loss spectroscopy were used to determine the elemental composition of the granules. Vacuolar granules
were amorphous and composed of silicon and oxygen, suggesting they consist of amorphous silica biominerals. No nitrogen, indicative
of organic matter, was detected in the granules.
Received November 26, 2001; accepted July 1, 2002; published online October 31, 2002
RID="*"
ID="*" Correspondence and reprints: Departamento de Microbiologia Geral, Instituto de Microbiologia Professor Paulo de Góes,
Centro de Ciências da Saude, Universidade Federal do Rio de Janeiro, 21941-590 Rio de Janeiro, RJ, Brazil. 相似文献
18.
Cytological evidence for preservation of mitochondrial and plastid DNA in the mature generative cells of Chlorophytum spp. (Liliaceae) 总被引:1,自引:0,他引:1
Summary. Following 4′,6-diamidino-2-phenylindole staining of mature pollen grains of Chlorophytum comosum, fluorescence microscopy confirmed that cytoplasmic nucleoids (DNA aggregates) were present in the generative cells, which
indicated the possibility of biparental cytoplasmic inheritance. Electron and immuno-electron microscopy showed that both
plastids and mitochondria were present in the generative cells, and both organelles contained DNA. These results indicate
that mitochondria and plastids of C. comosum have the potential for biparental inheritance. Similar results were obtained with mature pollen grains of C. chinense. Therefore, we conclude the coincident biparental inheritance for mitochondria and plastids in the members of the genus Chlorophytum.
Received June 28, 2002; accepted September 26, 2002; published online April 2, 2003
RID="*"
ID="*" Correspondence and reprints: College of Life Science, Peking University, Bejing 100871, People's Republic of China. 相似文献
19.
Ultrastructure of vascular cambial cell cytokinesis in pine seedlings preserved by cryofixation and substitution 总被引:4,自引:0,他引:4
Summary. Trees depend on the secondary vascular cambium to produce cells for new xylem and phloem. The fusiform cells of this lateral
meristem are long and narrow, presenting special challenges for arranging the mitotic spindle and phragmoplast. Fusiform cambial
cells of Pinus ponderosa and Pinus contorta were studied by cryofixation and cryosubstitution which preserved ultrastructure and phases of cytokinesis with a resolution
not previously attained. Membranous structures including the plasma membrane, tonoplast, and those of other organelles were
smooth and unbroken, indicating that they were preserved while the protoplasm was in a fully turgid state. Mitotic spindles
separated daughter chromosomes diagonally across the radial width of the cells. The cell plate was initiated at an angle to
the cell axis between the anaphase chromosomes by a microtubule array which organized vesicles at the phragmoplast midline.
Within the phragmoplast, vesicles initially joined across thin tubular projections and then amalgamated into a tubulo-vesicular
network. Axial expansion of the cell plate generated two opposing phragmoplasts connected by a thin, extended bridge of cell
plate and cytoplasm that was oriented along the cell axis. In the cytoplasmic bridge trailing each phragmoplast, the callose-rich
tubular network gradually consolidated into a fenestrated plate and then a complete cell wall. Where new membrane merged with
old, the parent plasmalemma appeared to be loosened from the cell wall and the membranes joined via a short tubulo-vesicular
network. These results have not been previously reported in cambial tissue, but the same phases of cytokinesis have been observed
in cryofixed root tips and suspension-cultured cells of tobacco.
Received February 11, 2002; accepted May 31, 2002; published online October 31, 2002
RID="*"
ID="*" Correspondence and reprints: Department of Botany, University of British Columbia, 6270 University Boulevard, Vancouver,
BC V6T 1Z4, Canada.
Abbreviations: CFS cryofixation and cryosubstitution; ER endoplasmic reticulum; HPF high-pressure freezing; PPB preprophase band. 相似文献
20.
Summary. The nature and specificity of the Wiesner test (phloroglucinol-HCl reagent) for the aromatic aldehyde fraction contained
in lignins is studied. Phloroglucinol reacted in ethanol-hydrochloric acid with coniferyl aldehyde, sinapyl aldehyde, vanillin,
and syringaldehyde to yield either pink pigments (in the case of hydroxycinnamyl aldehydes) or red-brown pigments (in the
case of hydroxybenzaldehydes). However, coniferyl alcohol, sinapyl alcohol, and highly condensed dehydrogenation polymers
derived from these cinnamyl alcohols and aldehydes did not react with phloroglucinol in ethanol-hydrochloric acid. The differences
in the reactivity of phloroglucinol with hydroxycinnamyl aldehydes and their dehydrogenation polymers may be explained by
the fact that, in the latter, the unsubstituted (α,β-unsaturated) cinnamaldehyde functional group, which is responsible for
the dye reaction, is lost due to lateral chain cross-linking reactions involving the β carbon. Fourier transform infrared
spectroscopy and thioacidolysis analyses of phloroglucinol-positive lignifying plant cell walls belonging to the plant species
Zinnia elegans L., Capsicum annuum var. annuum, Populus alba L., and Pinus halepensis L. demonstrated the presence of 4-O-linked hydroxycinnamyl aldehyde end groups and 4-O-linked 4-hydroxy-3-methoxy-benzaldehyde (vanillin) end groups in lignins. However, given the relatively low abundance of
4-O-linked vanillin in lignifying cell walls and the low extinction coefficient of its red-brown phloroglucinol adduct, it is
unlikely that vanillin contributes to a great extent to the phloroglucinol-positive stain reaction. These results suggest
that the phloroglucinol-HCl pink stain of lignifying xylem cell walls actually reveals the 4-O-linked hydroxycinnamyl aldehyde structures contained in lignins. Histochemical studies showed that these aldehyde structures
are assembled, as in the case of coniferyl aldehyde, during the early stages of xylem cell wall lignification.
Received April 17, 2002; accepted May 21, 2002; published online October 31, 2002
RID="*"
ID="*" Correspondence and reprints: Department of Plant Biology, University of Murcia, 30100 Murcia, Spain.
Abbreviations: DHP dehydrogenation polymers; FT-IR spectroscopy Fourier transform infrared spectroscopy. 相似文献