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1.
Summary Cortical cells of mycorrhizal roots undergo drastic morphological changes, such as vacuole fragmentation, nucleus migration,
and deposition of cell wall components at the plant-fungus interface. We hypothesized that the cytoskeleton is involved in
these mechanisms leading to cell reorganization. We subjected longitudinal, meristem to basal zone, sections of uninfectedNicotiana tabacum roots to immunofluorescence methods to identify the microtubular (MT) structures associated with root cells. Similar sections
were obtained from tobacco roots grown in the presence ofGigaspora margarita, an arbuscular mycorrhizal fungus which penetrates the root via the epidermal cells, but mostly develops in the inner cortical
cells. While the usual MT structures were found in uninfected roots (e.g., MTs involved in mitosis in the meristem and cortical
hoops in differentiated parenchyma cells), an increase in complexity of MT structures was observed in infected tissues. At
least three new systems were identified: (i) MTs running along large intracellular hyphae, (ii) MTs linking hyphae, (iii)
MTs binding the hyphae to the host nucleus. The experiments show that mycorrhizal infection causes reorganization of root
MTs, suggesting their involvement in the drastic morphological changes shown by the cortical cells. 相似文献
2.
Localized alteration in lateral root development in roots colonized by an arbuscular mycorrhizal fungus 总被引:1,自引:0,他引:1
The morphological responses of root systems to localized colonization by endophytes is not well understood. We examined the
responses of lateral roots to the arbuscular mycorrhizal (AM) fungus Gigaspora margarita Becker & Hall inoculated locally into the soil. Peanut (Arachis hypogaea L.) and pigeon pea (Cajanus cajan (L.) Millsp.) were examined. Root boxes filled with nutrient-poor soil in were inoculated in one half with the fungus and
in the other half with a sterilized inoculum. Responses were apparent after 30 days but not after 20 days. Overall, lateral
root development was more advanced in inoculated soil. This was clearly observed for 2nd- and 3rd-order lateral roots, but
less clear for 1st-order lateral roots in both species, although percentage of colonized root length was higher in 1st-order
lateral roots. Whilst in peanut the responses were clearly evident at the level of lateral roots initiated on more proximal
parts of the tap root axis, they occurred on more distal parts in pigeon pea. We conclude that plants under nutrient-poor
conditions give priority to mycorrhizal roots when partitioning assimilation products within the root system. Thus, AM formation
may induce local morphological alteration of root systems.
Accepted: 29 August 1996 相似文献
3.
J. POKORNÁ K. SCHWARZEROVÁ S. ZELENKOVÁ J. PETRÁEK I. JANOTOVÁ V. APKOVÁ & Z. OPATRNÝ 《Plant, cell & environment》2004,27(5):641-653
Cytoskeletal proteins assemble into dynamic polymers that play many roles in nuclear and cell division, signal transduction, and determination of cell shape and polarity. The distribution and dynamics of microtubules (MTs) and actin filaments (AFs) are determined, among other factors, by the location of their nucleation sites. Whereas the sites of microtubule nucleation in plants are known to be located under the plasma membrane and on the nuclear envelope during interphase, there is a striking lack of information about nucleation sites of AFs. In the studies reported herein, low temperature (0 °C) was used to de‐polymerize AFs and MTs in tobacco BY‐2 (Nicotiana tabacum L.) cells at interphase. The extent of de‐polymerization of cytoskeletal filaments in interphase cells during cold treatment and the subcellular distribution of nucleation sites during subsequent recovery at 25 °C were monitored by means of fluorescence microscopy. The results show that AFs re‐polymerized rapidly from sites located in the cortical region and on the nuclear envelope, similarly to the initiation sites of MTs. In contrast to MTs, however, complete reconstitution of AFs was preceded by the formation of transient actin structures including actin dots, rods, and filaments with a dotted signal. Immunoblotting of soluble and sedimentable protein fractions showed no changes in the relative amounts of free and membrane‐bound actin or tubulin. 相似文献
4.
5.
Hexokinases of tobacco leaves: influence of plant age on particulate and soluble isozyme composition
Changes in hexokinase particulate and soluble isozyme composition and activities in leaves of 65- and 115-d-old tobacco plants
were determined by ion exchange chromatography on DEAE cellulose. During plant ageing, the activities of glucose and of fructose
phosphorylating isozymes of particulate hexokinase decreased to 9.9 and 9.2 % of initial value, respectively. The activity
of soluble hexokinase decreased to a lesser extent: that of glucose phosphorylating isozyme to 49.8 % and of fructose phosphorylating
isozyme to 37.8 %. The activity of soluble fructokinase isozyme dropped to 34.8 %. Thus also the ratio of particulate and
soluble isozymes was dependent on the age of leaf tissue.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
6.
Walter Maier Jürgen Schmidt Victor Wray Michael Herbert Walter Dieter Strack 《Planta》1999,207(4):620-623
Tobacco (Nicotiana tabacum L.) plants were grown with and without the arbuscular mycorrhizal fungus, Glomus intraradices Schenk & Smith. High-performance liquid chromatographic analyses of methanolic extracts from mycorrhizal and non-mycorrhizal
tobacco roots revealed marked fungus-induced changes in the patterns of UV-detectable products. The UV spectra of these products,
obtained from an HPLC photodiode array detector, indicated the presence of several blumenol derivatives. The most predominant
compound among these derivatives was spectroscopically identified as 13-hydroxyblumenol C 9-O-gentiobioside (“nicoblumin”), i.e. the 9-O-(6′-O-β-glucopyranosyl)-β-glucopyranoside of 13-hydroxy-6-(3-hydroxybutyl)-1,1,5-trimethyl-4-cyclohexen-3-one, a new natural product.
This is the first report on the identification of blumenol derivatives in mycorrhizal roots of a non-gramineous plant.
Received: 28 August 1998 / Accepted: 26 October 1998 相似文献
7.
Changes in the number of protoplasts, viability, protein and chlorophyll content were studied in tobacco mesophyll protoplasts
cultivated either autotrophically in CPW medium with mannitol (MCPW) in the light or heterotrophically in CPW medium with
glucose (GCPW) in the dark. The number and viability of protoplasts in the both cultivation media were unchanged. In MCPW
in the light, the protein and chlorophyll content strongly decreased already after 12 h of cultivation, at 72 h of cultivation,
values dropped to 23.6 % (proteins) and to 3.5 % (chlorophyll) in comparison with the initial content. In GCPW in the dark,
the protein and chlorophyll contents decreased only slightly to 75 % (proteins) and to 57.7 % (chlorophyll). 相似文献
8.
9.
Jasplakinolide reversibly disrupts actin filaments in suspension-cultured tobacco BY-2 cells 总被引:3,自引:0,他引:3
Summary. Jasplakinolide is potentially a useful pharmacological tool for the study of actin organization and dynamics in living cells,
since it induces actin polymerization in vitro and, unlike phalloidin, is membrane permeative. In the present work, the effect
of jasplakinolide on the actin cytoskeleton of living suspension-cultured Nicotiana tabacum ‘Bright Yellow 2’ cells was investigated. Actin filaments in the living cells were disrupted by jasplakinolide. The effect
of jasplakionlide on the actin cytoskeleton was concentration and time dependent. When cells were treated with a moderate
concentration (150 nM) of jasplakinolide, cortical actin filaments were disrupted preferentially, whereas actin aggregated
at the perinuclear region. With concentrations higher than 400 nM and exposure times longer than 30 min, actin filaments in
the cell disappeared completely. The effect of jasplakinolide on the actin cytoskeleton was reversible even at high concentration.
Actin bundles appeared first in the perinuclear region within 5 min, and the cortical actin array was reestablished in 15 min,
suggesting that actin filaments might be organized at this region.
Received July 31, 2001 Accepted December 14, 2001 相似文献
10.
Early events responsible for aluminum toxicity symptoms in suspension-cultured tobacco cells 总被引:2,自引:0,他引:2
We investigated the aluminum (Al)-induced alterations in zeta potential, plasma membrane (PM) potential and intracellular calcium levels to elucidate their interaction with callose production induced by Al toxicity. A noninvasive confocal laser microscopy has been used to analyse the live tobacco (Nicotiana tabacum) cell events by means of fluorescent probes Fluo-3 acetoxymethyl ester (intracellular calcium) and DiBAC4 (PM potential) as well as to monitor callose accumulation. Log-phase cells showed no detectable changes in the PM potential during the first 30 min of Al treatment, but sustained large depolarization from 60 min onwards. Measurement of zeta potential confirmed the depolarization effect of Al, but the kinetics were different. The Al-treated cells showed a moderate increase in intracellular Ca2+ levels and callose production in 1 h, which coincided with the time course of PM depolarization. Compared with the Al treatment, cyclopiazonic acid, an inhibitor of endoplasmic reticulum Ca(2+)-ATPase, facilitated a higher increase in intracellular Ca2+ levels, but resulted in accumulation of only moderate levels of callose. Calcium channel modulators and Al induced similar levels of callose in the initial 1 h of treatment. Callose production induced by Al toxicity is dependent on both depolarization of the PM and an increase in intracellular Ca2+ levels. 相似文献
11.
G. LINGUA S. SGORBATI A. CITTERIO A. FUSCONI A. TROTTA E. GNAVI & G. BERTA 《The New phytologist》1999,141(1):161-169
Arbuscular mycorrhizas are a widespread symbiosis between soil fungi and plant roots. Flow cytometry, after DNase I partial digestion and DAPI staining, and light and electron microscopy were used to analyse chromatin condensation and nuclear conditions in mycorrhizal and control roots of Allium porrum . The 2C peak, detected by flow cytometry, split into two peaks representing two populations of nuclei, one more resistant and one more susceptible to the enzyme action. The microscopic analyses showed the presence of pyknotic and chromatolytic nuclei, two typical features of senescence. In order to quantify the senescing process, a terminal deoxynucleotidyl transferase assay was performed on extracted nuclei, later analysed by flow cytometry. The numbers of senescing nuclei and their DNA cleavage were higher in control plants. Our results show the existence of senescing nuclei in cortical cells of the bulbous monocotyledon A. porrum and the delaying effect of arbuscular mycorrhizas on senescence. 相似文献
12.
Development of flower buds in thin-layer cultures of floral stalk tissue from tobacco: Role of hormones in different stages 总被引:4,自引:0,他引:4
The in vitro development of flower buds was studied on tissue explants of epidermis and subepidermal cortex from the flower stalks of Nicotiana tabacum L. cv. Samsun. The number of flower buds formed depended mainly on cytokinin concentration. Auxin acted as a modifier in a complex way. In early development, NAA at 1 μ M decreased the number of buds initiated and delayed bud emergence. At a later stage, auxin promoted bud outgrowth at the same concentration. Optimal results were obtained when explants were first incubated at low auxin concentration for 3–5 days and subsequently transferred to an elevated auxin level. Physiological processes that lead to flower bud initiation start very soon after the onset of incubation. This was inferred from experiments whereby explants were first cultured at an inductive cytokinin concentration and then transferred to a non-inductive hormone level. 相似文献
13.
Ye Zhou Tatsuya Awano Toru Matoh Keiji Takabe 《Bioscience, biotechnology, and biochemistry》2017,81(5):899-905
Rhamnogalacturonan II (RG-II) is a region of pectin macromolecules that is present in plant primary cell walls. The RG-II region serves as the site of borate cross-linking within pectin, via which pectin macromolecules link together to form a gel. In this study, we examined whether RG-II is present in the cell plate, the precursor of primary cell walls that forms during cytokinesis. A structure inside dividing cells was labeled with a rabbit polyclonal anti-RG-II antibody and detected by immunofluorescence microscopy. An antibody against callose, a marker polysaccharide for the cell plate, also labeled the structure. In immunoelectron microscopy analyses using the anti-RG-II antibody, gold particles were distributed in electron-lucent vesicular structures that appeared to correspond to the forming cell plates in late anaphase cells. Together, these results suggest that RG-II is present in cell plates from the early phase of their assembly. 相似文献
14.
In arbuscular mycorrhizas, H+-ATPase is active in the plant membrane around arbuscules but absent from plant mutants defective in arbuscule development
(Gianinazzi-Pearson et al. 1995, Can J Bot 73: S526–S532). The proton-pumping H+-ATPase is encoded by a family of genes in plants. Immunocytochemical studies and promoter-gusA fusion assays were performed in transgenic tobacco (Nicotiana tabacum L.) to determine whether the periarbuscular enzyme activity results from de-novo activation of plant genes by an arbuscular
mycorrhizal fungus. The H+-ATPase protein was localized in the plant membrane around arbuscule hyphae. The enzyme was absent from non-colonized cortical
cells. Regulation of seven H+-ATPase genes (pma) was compared in non-mycorrhizal and mycorrhizal roots by histochemical detection of β-glucuronidase (GUS) activity. Two
genes (pma2, pma4) were induced in arbuscule-containing cells of mycorrhizal roots but not in non-mycorrhizal cortical tissues or senescent
mycorrhiza. It is concluded that de-novo H+-ATPase activity in the periarbuscular membrane results from selective induction of two H+-ATPase genes, which can have diverse roles in plant-fungal interactions at the symbiotic interface.
Received: 23 October 1999 / Accepted: 7 February 2000 相似文献
15.
We investigated the accumulation of reactive oxygen species (ROS) in arbuscular mycorrhizal (AM) roots from Medicago truncatula, Zea mays and Nicotiana tabacum using three independent staining techniques. Colonized root cortical cells and the symbiotic fungal partner were observed to be involved in the production of ROS. Extraradical hyphae and spores from Glomus intraradices accumulated small levels of ROS within their cell wall and produced ROS within the cytoplasm in response to stress. Within AM roots, we observed a certain correlation of arbuscular senescence and H2O2 accumulation after staining by diaminobenzidine (DAB) and a more general accumulation of ROS close to fungal structures when using dihydrorhodamine 123 (DHR 123) for staining. According to electron microscopical analysis of AM roots from Z. mays after staining by CeCl3, intracellular accumulation of H2O2 was observed in the plant cytoplasm close to intact and collapsing fungal structures, whereas intercellular H2O2 was located on the surface of fungal hyphae. These characteristics of ROS accumulation in AM roots suggest similarities to ROS accumulation during the senescence of legume root nodules. 相似文献
16.
Deletion of a large genomic segment in tobacco varieties that are resistant to potato virus Y (PVY) 总被引:3,自引:0,他引:3
Noguchi S Tajima T Yamamoto Y Ohno T Kubo T 《Molecular & general genetics : MGG》1999,262(4-5):822-829
Recessive alleles (va, va
1
, va
2
, etc) of the tobacco Va locus confer resistance to potato virus Y (PVY). To elucidate the mechanism underlying this resistance, we attempted to identify
randomly amplified polymorphic (RAPD) markers that reveal polymorphism between two nearly isogenic lines (NILs) that differ
in their susceptibility to PVY. Using each of 500 primers and 800 pairs of primers, we identified over 100 RAPD fragments
that differed between the NILs. We applied these RAPD primers or primer combinations to an F2 population obtained from a cross between the susceptible line BY4 and the resistant va
2
-bearing NIL, F55. It was found that only 10 RAPD markers were polymorphic between resistant and susceptible plants. Unexpectedly,
these markers were all linked to Va. All 10 RAPD markers were present in all 8 susceptible varieties tested. At least one RAPD marker was not detected in 8 out
of 10 resistant varieties. Southern analysis revealed that the sequences of markers were not present in the genomes of resistant
varieties, and the markers were found in individually distinct positions on the chromosomes of susceptible tobacco varieties.
These results strongly suggest that the resistance conferred by va is due to deletions at the Va locus governing susceptibility to PVY.
Received: 20 May 1999 / Accepted: 17 August 1999 相似文献
17.
Recent advances in cytokinin analysis have made it possible to measure the content of 22 cytokinin metabolites in the tissue of developing tobacco seedlings. Individual types of cytokinins in plants are interconverted to their respective forms by several enzymatic activities (5'-AMP-isopentenyltransferase, adenosine nucleosidase, 5'-nucleotidase, adenosine phosphorylase, adenosine kinase, trans-hydroxylase, zeatin reductase, beta-glucosidase, O-glucosyl transferase, N-glucosyl transferase, cytokinin oxidase). This paper reports modelling and measuring of the dynamics of endogenous cytokinins in tobacco plants grown on media supplemented with isopentenyl adenine (IP), zeatin (Z) and dihydrozeatin riboside (DHZR). Differences in phenotypes generated by the three cytokinins are shown and discussed, and the assumption that substrate concentration drives enzyme kinetics underpinned the construction of a simple mathematical model of cytokinin metabolism in developing seedlings. The model was tested on data obtained from liquid chromatography/tandem mass spectrometry cytokinin measurements on tobacco seedlings grown on Murashige and Skoog agar nutrient medium, and on plants grown in the presence of IP, Z and DHZR. A close match was found between measured and simulated data, especially after a series of iterative parameter searches, in which the parameters were set to obtain the best fit with one of the data sets. 相似文献
18.
19.
Suspension cultures of tobacco cells were grown in B5 media supplemented with sucrose, glucose, mannitol and sorbitol as exogenous
sugars to examine culture-induced changes in the osmolality of the medium. Osmolality decreases were greatest in sucrose and
glucose media during the 14 days in culture, and in glucose media were essentially linear, presumably reflecting the use of
this sugar as a food source. Osmolality decreases occurred during the first week of culture in mannitol- and sorbitol-supplemented
media, but later stabilized. Fresh weight of cultured cells in sucrose- and glucose-supplemented media increased by <200%
during 14 days in culture, whereas cultured cells in mannitol- and sorbitol-supplemented media increased by only 39 and 48%,
respectively. Cells transferred to the original liquid medium (B5 medium with 3% sucrose and 3% glucose) grew vigorously if
they had been cultured in sucrose- and glucose-supplemented media; however, cells grown in mannitol- and sorbitol-supplemented
media needed to be subcultured several times to recover their normal growth rate. By subculturing cells into increasingly
higher conditions of sugars, cells tolerant to 560 mOsmol kg-1 H2O were obtained. The high osmolality-adapted cells increased
by 140% in fresh weight in 8% glucose-supplemented medium. Glucose was best suited for producing the high osmolality required
because sucrose concentrations at 10% sucrose and above resulted in cell death. To limit the decrease of osmolality in these
suspension cultures requires changing the medium every 3 days to maintain osmolality above the 530 mOsmol kg-1 H2O needed
to co-culture these as feeder cells with gametic and zygotic cells.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
20.
Momoyama Y Miyazawa Y Miyagishima SY Mori T Misumi O Kuroiwa H Tsuneyoshi K 《European journal of cell biology》2003,82(6):323-332
Plastids, an essential group of plant cellular organelles, proliferate by division to maintain continuity through cell lineages in plants. In recent years, it was revealed that the bacterial cell division protein FtsZ is encoded in the nuclear genome of plant cells, and plays a major role in the plastid division process forming a ring along the center of plastids. Although the best-characterized type of plastid division so far is the division with a single FtsZ ring at the plastid midpoint, it was recently reported that in some plant organs and tissues, plastids are pleomorphic and form multiple FtsZ rings. However, the pleomorphic plastid division mechanism, such as the formation of multiple FtsZ rings, the constriction of plastids and the behavior of plastid (pt) nucleoids, remains totally unclear. To elucidate these points, we used the cultured cell line, tobacco (Nicotiana tabacum L.) Bright Yellow-2, in which plastids are pleomorphic and show dynamic morphological changes during culture. As a result, it was revealed that as the plastid elongates from an ellipsoid shape to a string shape after medium renewal, FtsZ rings are multiplied almost orderly and perpendicularly to the long axis of plastids. Active DNA synthesis of pt nucleoids is induced by medium transfer, and the division and the distribution of pt nucleoids occur along with plastid elongation. Although it was thought that the plastid divides with simultaneous multiple constrictions at all the FtsZ ring sites, giving rise to many small plastids, we found that the plastids generally divide constricting at only one FtsZ ring site. Moreover, using electron microscopy, we revealed that plastid-dividing (PD) rings are observed only at the constriction site, and not at swollen regions. These results indicate that in the pleomorphic plastid division with multiple FtsZ rings, the formation of PD rings occurs at a limited FtsZ ring site for one division. Multiplied FtsZ rings seem to localize in advance at the expected sites of division, and the formation of a PD ring at each FtsZ ring site occurs in a certain order, not simultaneously. Based on these results, a novel model for the pleomorphic plastid division with multiple FtsZ rings is proposed. 相似文献