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1.
细胞外基质在植物发育中的作用   总被引:6,自引:1,他引:5  
植物细胞壁是由纤维素和果胶交联的多糖和蛋白质构成的既彼此独立,又相互作用的三维动力学网络。和动物的细胞外基质一样,植物细胞壁中的许多成分积极地参与植物细胞发育过程的调节,它们以某种方式将信息传递给细胞,调节细胞的行为,以便对各种外界环境作出相应的反应。因此细胞壁不再是一种环绕植物细胞的惰性结构,比起细胞壁,植物细胞外基质这一名词更能反映出这一动力学的特性。  相似文献   

2.
绝大多数植物细胞的质膜外都有细胞壁,这是区别予动物细胞的显著特征之一。由于细胞壁的存在,使原生质体的膨胀受到限制,细胞成熟后,使其形态和大小变为固定。细胞壁有保护作用,厚而硬的细胞壁还有支持植物器官的机械作用,同时,细胞壁能影响植物组织的吸收、蒸腾、运输和分泌等功能。  相似文献   

3.
水分亏缺下细胞延伸生长与细胞膨压和细胞壁特性的关系   总被引:17,自引:1,他引:16  
在简要介绍植物细胞延伸生长的生物物理模型的基础上,综述了水分亏缺下植物细胞延伸生长与细胞膨压、细胞壁伸展性和细胞壁塑变阈值的关系,阐述了植物细胞壁调节在作物抗旱性中的作用。  相似文献   

4.
细胞壁与细胞的发育   总被引:1,自引:0,他引:1  
细胞壁除了起着机械支持、参与物质运输和防御反应等功能外,与细胞的发育密切相关。它们可作为信号分子,促进植物细胞的分裂增殖,决定细胞的分化方向,参与细胞识别过程等。概述了近年来细胞壁调节细胞发育的新进展。  相似文献   

5.
植物细胞壁作为细胞外复杂交联网络,为植物细胞生长、发育以及适应环境变化提供机械支撑,具有调节植物形态、抵抗胁迫、运输水分等功能。除此之外,植物光合作用积累的生物质大部分贮藏在细胞壁中,因此,研究细胞壁的成分和纳微结构对更好的利用植物能源具有重要意义。植物细胞壁的结构研究是当今植物界研究的前沿热点之一。随着新型成像技术的发展,近年来关于细胞壁成分和纳微结构的研究取得了阶段性的进展。本文就植物细胞壁的成分、结构、成像技术和力学性质进行了总结与展望,以期为植物细胞壁的相关研究提供新思路。  相似文献   

6.
基质金属蛋白酶与心肌重塑   总被引:1,自引:0,他引:1  
细胞外基质参与和促进了心肌重塑的过程,基质金属蛋白酶是调节细胞外基质重要的酶,基质金属蛋白酶在心肌重塑过程表达变化可分为三个时相,其活性受到信号传导途径、炎症因子和活性氧/活性氮的调节,基质金属蛋白酶可能作为心肌梗塞等疾病治疗的靶标  相似文献   

7.
气孔运动调节植物的光合作用和蒸腾作用,对植物的生长发育和干旱等非生物胁迫的响应都起到重要的作用。保卫细胞能够通过感知胞内和胞外多种信号调节气孔开度,因此,保卫细胞已经成为植物细胞信号转导研究中广泛应用的细胞模型。该文对保卫细胞中微丝骨架和活性氧对气孔运动的调节作用、微丝骨架在调节细胞壁与质膜间联系中的作用进行了综述,最后分析了微丝骨架通过ROS(reactive oxygen species)调节保卫细胞壁–质膜联系参与气孔运动调控的可能机制。  相似文献   

8.
细胞与细胞外基质的相互作用以及细胞外基质的重构在脂肪组织的形成过程中发挥了重要作用。细胞外基质的这一系列变化是由细胞分泌的蛋白酶及其抑制物调控的,其中基质金属蛋白酶(MMPs)是一类调控细胞外基质分解的蛋白酶家族。MMPs的活性受其四种组织抑制物调节,即TIMP1-4。以前对TIMP在脂  相似文献   

9.
近年来的研究表明,Ca2+在植物细胞的信号转导过程中一直起着非常重要的作用。通常,生活细胞内游离钙的浓度保持在30—200nmol/L的范围内, 但来自细胞外或细胞内的各种刺激,则可引起细胞内游离钙浓度的瞬时变化,从而使Ca2+通过不同的信号转导途径,直接或间接地调节细胞生理和生化过程。在植物细胞的生命活动过程中,Ca2+的调节功能表现为多种多样,其中包括离子运输、细胞运动、糖类代谢、细胞分裂、细胞分泌以及基因表达等等。有人研究发现,在植物细胞间隙、细胞壁以及液泡中Ca2+的浓度远高于细胞内游离钙浓度,它们是细胞质…  相似文献   

10.
整合素及其在胚泡植入中的作用   总被引:5,自引:0,他引:5       下载免费PDF全文
整合素是一类由α、β亚基构成的异二聚体粘附分子,能够与胶原蛋白、纤连蛋白和玻连蛋白等细胞外基质组分相互作用,调节细胞粘附和通讯.作为双向传递分子,整合素通过“胞内→胞外”和“胞外→胞内”两种方式介导细胞信号传递.成功的植入是侵入性的胚泡和接受性的子宫内膜相互作用的结果,整合素能够调节胚泡滋养层与子宫内膜之间的细胞-细胞及细胞-细胞外基质相互作用,是“植入窗口”期子宫内膜接受性的标记分子.  相似文献   

11.
Rapid cellular responses to auxin and the regulation of growth   总被引:4,自引:4,他引:0  
Abstract The cellular responses rapidly evoked by auxin are reviewed, and related to a consideration of how growth rate is regulated in excised segments and in whole dicotyledonous plants. Two processes, synthesis of proteins and of cell wall components, are both promoted by auxin and essential for auxin-stimulated growth, whereas other processes show little promotion by auxin or do not appear essential for growth. Current models for the cellular regulation of growth by auxin are briefly discussed, and a new model presented. Auxin is suggested to act by bringing about a transient increase in cytosolic Ca2+ levels, which through the stimulation of protein kinases converts a cytoplasmic protein factor to an active state capable of binding auxin. The protein-auxin complex induces mRNA synthesis, which effects the increased synthesis of cell wall components and their incorporation into the wall, resulting in wall loosening and growth. It is proposed that the factor limiting growth in floating excised segments may initially be cell wall pH, but that this is not the case in whole plants and growth is instead mediated by increased protein and matrix cell wall synthesis. Differences are noted between monocotyledonous coleoptiles and dicotyledonous stems in some metabolic processes possibly involved in auxin growth responses, and it is cautioned that observations made on one tissue may not necessarily be applicable to the other. Care should also be taken in applying conclusions drawn from studies on excised tissue to the interpretation of growth regulation in the whole plant.  相似文献   

12.
Plant cells are surrounded by a dynamic cell wall that performs many essential biological roles, including regulation of cell expansion, the control of tissue cohesion, ion-exchange and defence against microbes. Recent evidence shows that the suite of polysaccharides and wall proteins from which the plant cell wall is composed shows variation between monophyletic plant taxa. This is likely to have been generated during the evolution of plant groups in response to environmental stress. Understanding the natural variation and diversity that exists between cell walls from different taxa is key to facilitating their future exploitation and manipulation, for example by increasing lignocellulosic content or reducing its recalcitrance for use in biofuel generation.  相似文献   

13.
14.
Students of metazoan biology have traditionally viewed the extracellular matrix (ECM) as a substrate with which cells interact to participate in developmental pattern formation and define a specific location. In contrast, the plant cell wall has been viewed as a cage that limits and thus directs plant cell morphology, and perhaps for this reason many have shied away from calling the plant cell wall the ECM. The recent discovery of a variety of receptor molecules and their ligands on the surface of plant cells and the intimate role cell walls play in development should direct our thinking toward a more dynamic view of the plant cell wall. A recent example, is the discovery of wall associated kinases (WAKs), which may well signal between the ECM and the cell and are required for cell expansion.  相似文献   

15.
Application of patch clamp techniques to higher-plant cells has been subject to the limitation that the requisite contact of the patch electrode with the cell membrane necessitates prior enzymatic removal of the plant cell wall. Because the wall is an integral component of plant cells, and because cell-wall-degrading enzymes can disrupt membrane properties, such enzymatic treatments may alter ion channel behavior. We compared ion channel activity in enzymatically isolated protoplasts of Vicia faba guard cells with that found in membranes exposed by a laser microsurgical technique in which only a tiny portion of the cell wall is removed while the rest of the cell remains intact within its tissue environment. "Laser-assisted" patch clamping reveals a new category of high-conductance (130 to 361 pS) ion channels not previously reported in patch clamp studies on plant plasma membranes. These data indicate that ion channels are present in plant membranes that are not detected by conventional patch clamp techniques involving the production of individual plant protoplasts isolated from their tissue environment by enzymatic digestion of the cell wall. Given the large conductances of the channels revealed by laser-assisted patch clamping, we hypothesize that these channels play a significant role in the regulation of ion content and electrical signalling in guard cells.  相似文献   

16.
17.
Cell adhesions mediate important bidirectional interactions between cells and the extracellular matrix. They provide an interactive interface between the extracellular chemical and physical environment and the cellular scaffolding and signaling machinery. This dynamic, reciprocal regulation of intracellular processes and the matrix is mediated by membrane receptors such as the integrins, as well as many other components that comprise the adhesome. Adhesome constituents assemble themselves into different types of cell adhesion structures that vary in molecular complexity and change over time. These cell adhesions play crucial roles in cell migration, proliferation, and determination of cell fate.With the emergence of metazoan life approximately 600 million years ago, new biological mechanisms arose during the evolution of multicellular organisms with a defined body plan. These mechanisms of cell adhesion are a fundamental feature of all metazoans, from sponges to humans; they enable cells to attach to each other or to an extracellular matrix (ECM), cementing them together and organizing them into a coherent whole. The formation of adhesions and the regulation of their dynamics are crucial for embryogenesis, immune cell function, and wound repair, but they also contribute to disease, including cancer invasion and metastasis, or immune disorders (Hay 1991; Hynes 2002; Berrier and Yamada 2007; Alberts et al. 2008; Mory et al. 2008; Dubash et al. 2009; Manevich-Mendelson et al. 2009; Svensson et al. 2009; Wolfenson et al. 2009a). Adhesive interactions can occur with remarkable temporal and spatial precision. As illustrated in Figure 1, they not only link cells together into functional tissues and organs, but they also convey to the adhering cells accurate positional information concerning their cellular and extracellular environment. This information can, in turn, affect all facets of the cell’s life—its proliferation, differentiation, and fate. In addition to responding to the matrix, cell adhesions can actively remodel and restructure the ECM, driving a reciprocal, bidirectional interaction between the cell and its surrounding matrix. These two fundamental aspects of cell–ECM adhesion—physical/structural roles and environmental sensing/signaling, as well as the dynamic molecular interrelationships between them—will be the primary subjects of this article.Open in a separate windowFigure 1.Schematic illustration highlighting the dynamic cross talk between cells and the extracellular matrix (ECM). Cells secrete and remodel the ECM, and the ECM contributes to the assembly of individual cells into tissues, affecting this process at both receptor and cytoskeletal levels. Adhesion-mediated signaling, based on the cells’ capacity to sense the chemical and physical properties of the matrix, affects both global cell physiology and local molecular scaffolding of the adhesion sites. The molecular interactions within the adhesion site stimulate, in turn, the signaling process, by clustering together the structural and signaling components of the adhesome.We will also describe the functional molecular architecture of cell–matrix adhesions, highlighting the structure–function relationships between the numerous components of cell adhesions that mediate or modulate numerous cell adhesive, migratory, and regulatory processes. We will discuss the mechanisms underlying the scaffolding and sensing processes generated at integrin-mediated adhesions, considering them along two major multiscale conceptual trajectories: molecular complexity and time—that is, a hierarchy of complexity that spans the range from molecules to multimolecular complexes in mature adhesions, as well as the temporal progression of structures during the assembly and maturation of matrix adhesions, from initial cell–matrix recognition to the formation, maturation, and reorganization of cytoskeleton-associated matrix adhesions.  相似文献   

18.
The enzyme α-1,6-mannosyltransferase (OCH-1) is required for the synthesis of galactomannans attached to the N-linked oligosaccharides of Neurospora crassa cell wall proteins. The Neurospora crassa och-1 mutant has a tight colonial phenotype and a defective cell wall. A carbohydrate analysis of the och-1 mutant cell wall revealed a 10-fold reduction in the levels of mannose and galactose and a total lack of 1,6-linked mannose residues. Analysis of the integral cell wall protein from wild-type and och-1 mutant cells showed that the mutant cell wall had reduced protein content. The och-1 mutant was found to secrete 18-fold more protein than wild-type cells. Proteomic analysis of the proteins released by the mutant into the growth medium identified seven of the major cell wall proteins. Western blot analysis of ACW-1 and GEL-1 (two glycosylphosphatidylinositol [GPI]-anchored proteins that are covalently integrated into the wild-type cell wall) showed that high levels of these proteins were being released into the medium by the och-1 mutant. High levels of ACW-1 and GEL-1 were also released from the och-1 mutant cell wall by subjecting the wall to boiling in a 1% SDS solution, indicating that these proteins are not being covalently integrated into the mutant cell wall. From these results, we conclude that N-linked mannosylation of cell wall proteins by OCH-1 is required for their efficient covalent incorporation into the cell wall.The fungal cell wall is an important organelle that protects the cell from various environmental stresses. It is a dynamic structure that interacts with the environment and is modified to accommodate growth, cell division, and development. Fungal cell walls have been shown to contain β-1,3-glucan, α-1,3-glucan, β-1,6-glucan, mixed β-1,3/β-1,4-glucans, chitin, and mannan/galactomannan (6, 19). These polysaccharide polymers constitute 80 to 85% of the cell wall mass, while glycoproteins constitute the remaining 15 to 20% (6). The cell wall glycoproteins are required for vital functions, like structural support, signal transduction, biofilm formation, and cell wall biosynthesis. In the case of pathogenic fungi, the cell wall is critical for the invasion of host tissues (8). Because of their accessibility and the crucial functions they perform, cell wall proteins could be important targets for the development of antifungal therapeutics.The glucan and chitin cell wall polymers are synthesized by enzyme complexes (glucan synthases and chitin synthases) that are associated with the plasma membrane. Glucan and chitin are vectorially passed into the cell wall space during synthesis and cross-linked together in the cell wall space. The mannan and galactomannan present in the cell wall are found as glycoconjugates on cell wall proteins. Mannosylation of cell wall proteins occurs in the endoplasmic reticulum (ER) and Golgi apparatus at O-linked and N-linked glycosylation sites. In Saccharomyces cerevisiae, mannosylation of N-linked glycosylation is initiated by the addition of an α-1,6-linked mannose residue by Och1p (33). In the filamentous fungus Neurospora crassa, the structure of the galactomannan associated with N-linked sites has not been definitively determined, but N. crassa has most of the enzymes defined in yeast for the mannosylation of N-linked oligosaccharides (14). An analysis of N-linked oligosaccharides from N. crassa glycoproteins showed that the glycoproteins are modified by the addition of short α-1,6-mannans with short α-1,2-mannose branches that are terminated by galactofuranose residues (31, 32). The N. crassa posttranslational modifications appear to differ from those found in S. cerevisiae by having shorter mannan chains and by the presence of terminal galactofuranose residues.Mannosylation of glycoproteins has been extensively studied in yeast. In S. cerevisiae, OCH1 encodes the α-1,6-mannosyltransferase enzyme that mediates the addition of the initial α-1,6-mannose in the synthesis of long mannans which are attached to the N-linked oligosaccharides (22, 33). Knockout mutants of OCH1 are viable but exhibit a temperature-sensitive growth pattern and are sensitive to cell wall perturbation reagents (34). Mutants for Candida albicans homologs of OCH1 had near-normal growth rates but were much less virulent (3). Mass spectrometry analysis of glycoproteins from the S. cerevisiae och1 and C. albicans och1 mutants showed that the α-1,6-mannose core was absent (3, 33). In Kluyveromyces lactis, the KlOCH1 gene has been shown to be important for cell wall organization and to give a hypersecretion phenotype (37). OCH1 mutants have also been identified in Pichia angusta, Yarrowia lipolytica, Pichia pastoris, and Schizosaccharomyces pombe, and these mutants have cell wall-related phenotypes (2, 9, 17, 38). However, a recent report of OCH1 knockout mutants of Aspergillus fumigatus indicates that these mutants do not have a cell wall-defective phenotype (18).Mannosylation of cell wall proteins has not been extensively studied in filamentous fungi. We report on the characterization of the N. crassa knockout mutant of the α-1,6-mannosyltransferase, och-1. The mutant was generated by the Neurospora genome knockout project (10). The N. crassa och-1 mutant has a severe growth defect and exhibits a tight colonial phenotype. We demonstrate that the och-1 mutant exhibits a defect in cell wall biosynthesis. A carbohydrate analysis of the mutant cell wall showed a drastic reduction in mannose and galactose content with a compensatory increase in the glucose content. The och-1 cell wall also showed a reduced cell wall protein content as assessed by a Coomassie brilliant blue dye binding assay and by proteomic analysis. Protein secretion assays showed that the mutant releases large amounts of cell wall protein into the growth medium. We demonstrate that the och-1 mutant is defective in covalently cross-linking known cell wall proteins into the cell wall matrix. Our data demonstrate that the N-linked galactomannan, which is built upon the mannose residue added by OCH-1, is required for the incorporation of cell wall proteins into the cell wall matrix.  相似文献   

19.
Summary Secretory vesicles involved in cell wall synthesis (wall vesicles) and the Golgi apparatus have been compared in conventionally fixed and freeze substituted hyphae of the oomycete fungusSaprolegnia ferax. Wall vesicles freeze substituted in various fluids range from spherical to tubular and contain an intensely staining, phosphorous rich matrix. In contrast diverse conventional fixations cause artefactual constrictions in most tubular vesicles and loss of their intensely staining contents. These data are interpreted to show the existence of an intravesicular skeletal system, with cellular regulation, to determine vesicle morphology and intravesicular synthesis of a hypothetical phosphorylated glycolipid cell wall precursor. Whilst freeze substitution gives superior preservation of wall vesicle morphology, it does not demonstrate any preferential association between wall vesicles and microtubules thus suggesting that microtubules are only indirectly involved in wall vesicle transport. Freeze substitution is superior to conventional fixation for analysis of the Golgi apparatus because it uniquely reveals both differentiation of a specific single cisterna in each Golgi body and greater differences in membrane thicknesses throughout the endomembrane system.  相似文献   

20.
All animal cell types have an appropriate volume. Even under physiological conditions of constant extracellular osmolarity, cells must regulate their volume. Cell volume is subjected to alterations because of persistent physicochemical osmotic load resulting from Donnan-type colloid osmotic pressure and of cell activity-associated changes in intracellular osmolarity resulting from osmolyte transport and metabolism. The strategy adopted by animal cells for coping with volume regulation on osmotic perturbation is to activate transport pathways, including channels and transporters, mainly for inorganic osmolytes to drive water flow. Under normotonic conditions, cells undergo volume regulation by pump-mediated mechanisms. Under anisotonic conditions, volume regulation occurs by additional channel/transporter-mediated mechanisms. Cell volume regulation is also attained through adjustment of intracellular levels not only of inorganic but also of organic osmolytes with changing the expression of their transporters or regulation of metabolism. In cell volume regulation mechanism, several "volume sensors" are thought to be involved. A volume-sensitive Cl- channel has lately attracted considerable attention in this regard.  相似文献   

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