共查询到20条相似文献,搜索用时 15 毫秒
1.
As plants lack immune cells, each cell has to defend itself against invading pathogens. Plant cells have a large central vacuole that accumulates a variety of hydrolytic enzymes and antimicrobial compounds, raising the possibility that vacuoles play a role in plant defense. However, how plants use vacuoles to protect against invading pathogens is poorly understood. Recently, we characterized two vacuole-mediated defense strategies associated with programmed cell death (PCD). In one strategy, vacuolar processing enzyme (VPE) mediated the disruption of the vacuolar membrane, resulting in the release of vacuolar contents into the cytoplasm in response to viral infection. In the other strategy, proteasome-dependent fusion of the central vacuole with the plasma membrane caused the discharge of vacuolar antibacterial protease and cell death-promoting contents from the cell in response to bacterial infection. Intriguingly, both strategies relied on enzymes with caspase-like activities: the vacuolar membrane-collapse system required VPE, which has caspase-1-like activity and the membrane-fusion system required a proteasome that has caspase-3-like activity. Thus, plants may have evolved a cellular immune system that involves vacuolar membrane collapse to prevent the systemic spread of viral pathogens and membrane fusion to inhibit the proliferation of bacterial pathogens.Key words: plant-pathogen interaction, vacuole, hypersensitive cell death, caspase activity, vacuolar processing enzyme, proteasome 相似文献
2.
New insights into the tonoplast architecture of plant vacuoles and vacuolar dynamics during osmotic stress 总被引:1,自引:0,他引:1
Background
The vegetative plant vacuole occupies >90% of the volume in mature plant cells. Vacuoles play fundamental roles in adjusting cellular homeostasis and allowing cell growth. The composition of the vacuole and the regulation of its volume depend on the coordinated activities of the transporters and channels localized in the membrane (named tonoplast) surrounding the vacuole. While the tonoplast protein complexes are well studied, the tonoplast itself is less well described. To extend our knowledge of how the vacuole folds inside the plant cell, we present three-dimensional reconstructions of vacuoles from tobacco suspension cells expressing the tonoplast aquaporin fusion gene BobTIP26-1::gfp. 相似文献3.
Vacuoles are suggested to play crucial roles in plant defense-related cel death. During programmed cel death, previous live cel imaging studies have observed vacuoles to become simpler in structure and... 相似文献
4.
N. V. Obroucheva 《Russian Journal of Developmental Biology》2008,39(1):13-24
The review is dedicated to the role of cell elongation in plant growth and morphogenesis. The ratios of cell division to elongation, cell competence for the initiation of elongation, main features of the metabolism of elongating cells, and physiological processes realizing elongation have been considered on the examples of seed germination and growth of roots, stems, and leaves. A special attention was paid to the vacuole as a specific feature of plant cells, pathways of its formation, and its role in maintenance of ion and water homeostasis in the elongating cell. The plant can modify its morphology according to changes in the environmental conditions via cell elongation. 相似文献
5.
The vacuole is a characteristic organelle of plant cells and fulfills several important functions related to metabolism and growth of the cell. To shed light on the details of vacuolar structural changes in plant cells, we explored the three-dimensional organization and dynamics of living Nicotiana tabacum L. cv. Bright Yellow 2 cell vacuoles by real-time confocal time-lapse imaging. For imaging, the cells were pulse-labeled with the amphipathic styryl dye FM1-43 (N-(3-triethylammoniumpropyl)-4-(4-(dibutylamino)styryl)pyridinium dibromide), which is delivered to the plant vacuole by endocytic uptake and then incubated overnight. Imaging of the membrane-labeled vacuole revealed a complex vacuole morphology underlaid by constant remodeling. The vacuole is traversed by multiple transvacuolar strands which move along each other and fuse in multiple manners. New strands were created by fission of large membrane sheets. Endocytic vesicle trafficking was followed within the dynamic transvacuolar strands. The movement occurred in a stop-and-go fashion with an average vesicle velocity of 0.46 microm/s and a peak velocity of 0.82 microm/s. Transvacuolar-strand reduction and creation is a characteristic event observed during mitosis. Here we propose a mechanistic model for the alteration of the number of transvacuolar strands, on the basis of their fusion and fission. 相似文献
6.
Obrucheva NV 《Ontogenez》2008,39(1):15-27
The review is dedicated to the role of cell elongation in plant growth and morphogenesis. The ratios of cell division to elongation, cell competence for the initiation of elongation, main features of the metabolism of elongating cells, and physiological processes realizing elongation have been considered on the examples of seed germination and growth of roots, stems, and leaves. A special attention was paid to the vacuole as a specific feature of plant cells, pathways of its formation, and its role in maintenance of ion and water homeostasis in the elongating cell. The plant can modify its morphology according to changes in the environmental conditions via cell elongation. 相似文献
7.
Plant Sphingolipids Today ‐ Are They Still Enigmatic? 总被引:2,自引:0,他引:2
Abstract: Sphingolipids are a diverse group of lipids found in all eukaryotes and some bacteria, consisting of a hydrophobic ceramide and a hydrophilic head group. We have summarised the contemporary understanding of the structure of plant sphingolipids with an emphasis on glucosylceramides and inositolphosphorylceramides. Plant glucosylceramides are important structural components of plasma and vacuole membranes. Inositolphosphorylceramides have been identified as moieties of the glycosylphosphorylinositol (GPI) anchors of plant proteins targeted to the plasma membrane. In the last few years, progress has been made in the cloning of plant genes coding for enzymes involved in sphingolipid metabolism. As found in yeast and mammals, the plant sphingolipid pathway is a potential generator of powerful cell signals. The role of plant sphingolipid metabolites in programmed cell death and calcium influx is discussed. 相似文献
8.
Large vacuoles are characteristic of plant and fungal cells, and their origin has long attracted interest. The cellular slime mould provides a unique opportunity to study the de novo formation of vacuoles because, in its life cycle, a subset of the highly motile animal-like cells (prestalk cells) rapidly develops a single large vacuole and cellulosic cell wall to become plant-like cells (stalk cells). Here we describe the origin and process of vacuole formation using live-imaging of Dictyostelium cells expressing GFP-tagged ammonium transporter A (AmtA-GFP), which was found to reside on the membrane of stalk-cell vacuoles. We show that stalk-cell vacuoles originate from acidic vesicles and autophagosomes, which fuse to form autolysosomes. Their repeated fusion and expansion accompanied by concomitant cell wall formation enable the stalk cells to rapidly develop turgor pressure necessary to make the rigid stalk to hold the spores aloft. Contractile vacuoles, which are rich in H+-ATPase as in plant vacuoles, remained separate from these vacuoles. We further argue that AmtA may play an important role in the control of stalk-cell differentiation by modulating the pH of autolysosomes. 相似文献
9.
Masayoshi Maeshima Yoichi Nakanishi Chie Matsuura-Endo Yoshiyuki Tanaka 《Journal of plant research》1996,109(1):119-125
Plant growth results from the division, enlargement and specialization of cells. The two processes of the enlargement and
the differentiation of cells are not spatially separated in plant tissue. We focus our attention here on the enlargement and
elongation of cells. In most cases, growing plant cells contain a large central vacuole. The acid growth theory is based on
the space-filling function of the large vacuole. The active transport systems in the vacuolar membrane are essential for maintenance
of high osmotic pressure and for the expansion of the vacuole. The secondary active transport systems of the vacuole for sugars
and ions are driven by the proton-motive force which is generated by the vacuolar H+-ATPase and H+-translocating inorganic pyrophosphatase. In this review, the relationship between cell elongation and these enzymes of the
vacuolar membrane is emphasized. 相似文献
10.
Aleksandr Gavrin Brent N. Kaiser Dietmar Geiger Stephen D. Tyerman Zhengyu Wen Ton Bisseling Elena E. Fedorova 《The Plant cell》2014,26(9):3809-3822
In legume–rhizobia symbioses, the bacteria in infected cells are enclosed in a plant membrane, forming organelle-like compartments called symbiosomes. Symbiosomes remain as individual units and avoid fusion with lytic vacuoles of host cells. We observed changes in the vacuole volume of infected cells and thus hypothesized that microsymbionts may cause modifications in vacuole formation or function. To examine this, we quantified the volumes and surface areas of plant cells, vacuoles, and symbiosomes in root nodules of Medicago truncatula and analyzed the expression and localization of VPS11 and VPS39, members of the HOPS vacuole-tethering complex. During the maturation of symbiosomes to become N2-fixing organelles, a developmental switch occurs and changes in vacuole features are induced. For example, we found that expression of VPS11 and VPS39 in infected cells is suppressed and host cell vacuoles contract, permitting the expansion of symbiosomes. Trafficking of tonoplast-targeted proteins in infected symbiotic cells is also altered, as shown by retargeting of the aquaporin TIP1g from the tonoplast membrane to the symbiosome membrane. This retargeting appears to be essential for the maturation of symbiosomes. We propose that these alterations in the function of the vacuole are key events in the adaptation of the plant cell to host intracellular symbiotic bacteria. 相似文献
11.
Inositol trisphosphate is known to mobilize calcium from internal stores in plant cells. However, with the exception of the vacuole, the largest plant cell compartment, organelles responsive to inositol trisphosphate have not been extensively identified. In this way, we have separated membrane vesicles from the same carrot microsomal fraction and identified them, both by marker enzyme activities and electron microscopy. These correspond to pure plasma membrane, pure tonoplast and mixed mitochondria, endoplasmic reticulum, Golgi membrane fractions. All the fractions accumulated calcium in a ATP-dependent manner and were tightly sealed. Inositol trisphosphate-dependent calcium releases were accurately measured only in fractions corresponding functionally and structurally to tonoplast, the vacuolar membrane. The process was dose-dependent and fairly specific for inositol trisphosphate. While highly significant, approximately 40% of the mobile calcium only may be released from tonoplast vesicles by inositol trisphosphate which remained basically intact during the release experiments. From these results it is concluded that the vacuole is the richest store of calcium directly mobilizable by inositol trisphosphate in plant cells, but inositol trisphosphate is not able to release the overall mobile vacuolar calcium. 相似文献
12.
In plant cells, the vacuole functions as a major calcium store. Although a calmodulin-regulated Ca2+-ATPase (ACA4) is known to be present in prevacuolar compartments, the presence of an ACA-type Ca2+-ATPase in the mature vacuole of a plant cell has not been verified. Here we provide evidence that ACA11 localizes to the vacuole membrane. ACA11 tagged with GFP was expressed in stable transgenic plants, and visualized in root cells and protoplasts by confocal microscopy. A Ca2+-ATPase function for ACA11 was confirmed by complementation of yeast mutants. A calmodulin binding domain was identified within the first 37 residues of the N-terminal autoinhibitory region. 相似文献
13.
Hans J. Vogel Peter Lundberg Kirsten Bagh 《In vitro cellular & developmental biology. Plant》1999,35(2):144-151
Summary Nuclear magnetic resonance (NMR) spectroscopy provides a unique modality for the study of tissue-cultured plant cells. One
of its major attractions is that it allows noninvasive studies of plant material. In addition, it can provide insight into
the pH in the vacuole and cytoplasm, and into the compartmentalization of certain metabolites. In this review we show how
phosphorus-31 NMR is used to study intracellular pH, phosphate uptake and storage, and energy metabolism in suspension cells
of Catharanthus roseus. In addition, multinuclear NMR studies of the uptake of ammonium and the gradients of K+ over the membrane are discussed as well. The use of two-dimensional NMR for the study of whole cell extracts is also described.
Finally, we show how nitrogen-14 and nitrogen-15 NMR are used to obtain information about the assimilation of inorganic sources
in developing carrot somatic embryos. These NMR studies provide a unique insight into the metabolism of tissue-cultured plant
cells. 相似文献
14.
Mojgan Shahriari Channa Keshavaiah David Scheuring Aneta Sabovljevic Peter Pimpl Rainer E. Häusler Martin Hülskamp Swen Schellmann 《The Plant journal : for cell and molecular biology》2010,64(1):71-85
The vacuole is the most prominent organelle of plant cells. Despite its importance for many physiological and developmental aspects of plant life, little is known about its biogenesis and maintenance. Here we show that Arabidopsis plants expressing a dominant‐negative version of the AAA (ATPase associated with various cellular activities) ATPase AtSKD1 (SUPPRESSOR OF K+ TRANSPORT GROWTH DEFECT1) under the control of the trichome‐specific GLABRA2 (GL2) promoter exhibit normal vacuolar development in early stages of trichome development. Shortly after its formation, however, the large central vacuole is fragmented and finally disappears completely. Secretion assays with amylase fused to the vacuolar sorting signal of Sporamin show that dominant‐negative AtSKD1 inhibits vacuolar trafficking of the reporter that is instead secreted. In addition, trichomes expressing dominant‐negative AtSKD1 frequently contain multiple nuclei. Our results suggest that AtSKD1 contributes to vacuolar protein trafficking and thereby to the maintenance of the large central vacuole of plant cells, and might play a role in cell‐cycle regulation. 相似文献
15.
GORDON J. LEITCH MARY SCANLON GOVINDA S. VISVESVARA SARA WALLACE 《The Journal of eukaryotic microbiology》1995,42(5):445-451
ABSTRACT. Microsporidia of the genus Encephalitozoon undergo merogony and sporogony in a parasitophorous vacuole within the host cell. Cultured green monkey kidney cells infected with Encephalitozoon hellem were loaded with the fluorescent dyes fura-2 or BCECF in order to measure intracellular concentrations of calcium and hydrogen ions respectively. Both the parasitophorous vacuole calcium concentration and pH values resembled those of the host cell cytoplasm in infected cells. Calcein entered the parasitophorous vacuole but not other host cell vacuoles or parasite stages within the parasitophorous vacuole. The lack of a pH or calcium concentration gradient across the parasitophorous vacuole membrane and the permeability of this membrane to a large anion such as calcein suggest that the vacuole membrane surrounding E. hellem resembles that surrounding some other intracellular parasites such as Toxoplasma gondii. A potential role is discussed for the parasitophorous vacuole calcium concentration in germination in situ. 相似文献
16.
Within plant systems, two main forms of programmed cell death (PCD) exist: developmentally regulated and environmentally induced.
The lace plant (Aponogeton madagascariensis) naturally undergoes developmentally regulated PCD to form perforations between longitudinal and transverse veins over its
leaf surface. Developmental PCD in the lace plant has been well characterized; however, environmental PCD has never before
been studied in this plant species. The results presented here portray heat shock (HS) treatment at 55°C for 20 min as a promising
inducer of environmental PCD within lace plant protoplasts originally isolated from non-PCD areas of the plant. HS treatment
produces cells displaying many characteristics of developmental PCD, including blebbing of the plasma membrane, increased
number of hydrolytic vesicles and transvacuolar strands, nuclear condensation, terminal deoxynucleotidyl transferase-mediated
dUTP nick-end labeling positive nuclei, as well as increased Brownian motion within the vacuole. Results presented here for
the first time provide evidence of chloroplasts in the vacuole of living protoplasts undergoing environmentally induced PCD.
Findings suggest that the mitochondria play a critical role in the cell death process. Changes in mitochondrial dynamics were
visualized in HS-treated cells, including loss of mitochondrial mobility, reduction in ΔΨm, as well as the proximal association with chloroplasts. The role of the mitochondrial permeability transition pore (PTP)
was examined by pre-treatment with the PTP agonist cyclosporine A. Overall, HS is depicted as a reliable method to induce
PCD within lace plant protoplasts, and proves to be a reliable technique to enable comparisons between environmentally induced
and developmentally regulated PCD within one species of plant. 相似文献
17.
Calcium-Activated K+ Channels and Calcium-Induced Calcium Release by Slow Vacuolar Ion Channels in Guard Cell Vacuoles Implicated in the Control of Stomatal Closure 总被引:13,自引:4,他引:9
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Stomatal closing requires the efflux of K+ from the large vacuolar organelle into the cytosol and across the plasma membrane of guard cells. More than 90% of the K+ released from guard cells during stomatal closure originates from the guard cell vacuole. However, the corresponding molecular mechanisms for the release of K+ from guard cell vacuoles have remained unknown. Rises in the cytoplasmic Ca2+ concentration have been shown to trigger ion efflux from guard cells, resulting in stomatal closure. Here, we report a novel type of largely voltage-independent K+-selective ion channel in the vacuolar membrane of guard cells that is activated by physiological increases in the cytoplasmic Ca2+ concentration. These vacuolar K+ (VK) channels had a single channel conductance of 70 pS with 100 mM KCI on both sides of the membrane and were highly selective for K+ over NH4+ and Rb+. Na+, Li+, and Cs+ were not measurably permeant. The Ca2+, voltage, and pH dependences, high selectivity for K+, and high density of VK channels in the vacuolar membrane of guard cells suggest a central role for these K+ channels in the initiation and control of K+ release from the vacuole to the cytoplasm required for stomatal closure. The activation of K+-selective VK channels can shift the vacuolar membrane to more positive potentials on the cytoplasmic side, sufficient to activate previously described slow vacuolar cation channels (SV-type). Analysis of the ionic selectivity of SV channels demonstrated a Ca2+ over K+ selectivity (permeability ratio for Ca2+ to K+ of ~3:1) of these channels in broad bean guard cells and red beet vacuoles, suggesting that SV channels play an important role in Ca2+-induced Ca2+ release from the vacuole during stomatal closure. A model is presented suggesting that the interaction of VK and SV channel activities is crucial in regulating vacuolar K+ and Ca2+ release during stomatal closure. Furthermore, the possibility that the ubiquitous SV channels may represent a general mechanism for Ca2+-induced Ca2+ release from higher plant vacuoles is discussed. 相似文献
18.
Mariana Sottomayor Patrícia Duarte Raquel Figueiredo Alfonso Ros Barceló 《Plant signaling & behavior》2008,3(10):899-901
Plants possess a unique metabolic diversity commonly designated as secondary metabolism, of which the anticancer alkaloids from Catharanthus roseus are among the most studied. Recently, in a classical function-to-protein-to-gene approach, we have characterized the main class III peroxidase (Prx) expressed in C. roseus leaves, CrPrx1, implicated in a key biosynthetic step of the anticancer alkaloids. We have shown the vacuolar sorting determination of CrPrx1 using GFP fusions and we have obtained further evidence supporting the role of this enzyme in alkaloid biosynthesis, indicating the potential of CrPrx1 as a molecular tool for the manipulation of alkaloid metabolism. Here, we discuss how plant cells may regulate Prx reactions. In fact, Prxs form a large multigenic family whose members accept a broad range of substrates and, in their two subcellular localizations, the cell wall and the vacuole, Prxs co-locate with a large variety of secondary metabolites which can be accepted as substrates. How then, are Prx reactions regulated? Localization data obtained in our lab suggest that arabinogalactan proteins (AGPs) and Prxs may be associated in membrane microdomains, evocative of lipid rafts. Whether plasma membrane and/or tonoplast microcompartmentation involve AGPs and Prxs and whether this enables metabolic channeling determining Prx substrate selection are challenging questions ahead.Key words: class III peroxidases, CrPrx1, indole alkaloids, vacuole, secondary metabolites, arabinogalactan proteins, lipid rafts 相似文献
19.
The contractile vacuole complex of Dictyostelium is the paradigm of a membrane system that undergoes tubular-vesicular transitions during its regular cycle of activities. This system acts as an osmoregulatory organelle in freshwater amoebae and protozoa. It collects fluid in a network of tubules and cisternae, and pumps it out of the cell through transient pores in the plasma membrane. Tubules and vacuoles are interconvertible. The tubular channels are associated with the cortical actin network and are capable of moving and fusing. The contractile vacuole complex is separate from vesicles of the endosomal pathway and preserves its identity in a dispersed state during cell division. We outline techniques to visualize the contractile vacuole system by electron and light microscopy. Emphasis is placed on GFP-fusion proteins that allow visualization of the dynamics of the contractile vacuole network in living cells. Proteins that control activities of this specialized organelle in Dictyostelium have been conserved during evolution and also regulate membrane trafficking in man. 相似文献
20.
Peiter E 《Cell calcium》2011,50(2):120-128
This review portrays the plant vacuole as both a source and a target of Ca2+ signals. In plants, the vacuole represents a Ca2+ store of enormous size and capacity. Total and free Ca2+ concentrations in the vacuole vary with plant species, cell type, and environment, which is likely to have an impact on vacuolar function and the release of vacuolar Ca2+. It is known that cytosolic Ca2+ signals are often generated by release of the ion from internal stores, but in very few cases has a role of the vacuole been directly demonstrated. Biochemical and electrophysical studies have provided evidence for the operation of ligand- and voltage-gated Ca2+-permeable channels in the vacuolar membrane. The underlying molecular mechanisms are largely unknown with one exception: the slow vacuolar channel, encoded by TPC1, is the only vacuolar Ca2+-permeable channel cloned to date. However, due to its complex regulation and its low selectivity amongst cations, the role of this channel in Ca2+ signalling is still debated. Many transport proteins at the vacuolar membrane are also targets of Ca2+ signals, both by direct binding of Ca2+ and by Ca2+-dependent phosphorylation. This enables the operation of feedback mechanisms and integrates vacuolar transport systems in the wider signalling network of the plant cell. 相似文献