不同硼效率甘蓝型油菜品种细胞壁中硼的分配

应用不同硼效率甘蓝型油菜品种 ,研究硼在细胞壁中的分配。硼主要结合在细胞壁中 ,缺硼显著提高硼在细胞壁中的分配比例。根系细胞壁硼含量显著低于叶片 ,但根系细胞壁硼占根系总硼量之比例显著高于叶片。同一品种根系及其细胞壁、老叶细胞壁硼含量受生育期影响较小 ,新叶及其细胞壁、老叶硼含量受生育期影响较大。在正常供硼条件下 ,硼高效品种根系细胞壁和叶片细胞壁硼含量均低于低效品种 ;正常和缺硼条件下 ,硼高效品种细胞壁硼占器官总硼量之比例均低于低效品种。说明硼低效品种需较多的硼构建细胞壁。     

Cell wall functions in growth and development —a physical and chemical point of view

The plant cell changes its cell wall architecture during growth and development through synthesis and degradation of wall polysaccharides. Changes of chemical components in the cell wall include not only the synthesis and degradation but also the shift of molecular-weight distribution of certain species of the component polysaccharides. The changes in chemical structure, in turn lead to alteration of physical properties of the cell wall. Changes of physical parameters of cell walls obtained by a physical method accord with the biochemical degradation of polysaccharides. The changes in chemical structures of the cell wall are regulated by plant hormones, stress signals and gene expression. The physical and chemical studies of the cell wall have disclosed that degradation and/or depolymerization of wall polysaccahrides causes decrease in viscosity of the cell wall, leading further extension of the cell wall even under the unchanged osmotic relation. Furthermore, cell walls of outer and inner tissues play different regulatory roles in tissue growth and stem strength was governed by the number of cellulose molecules in the cell wall. Recipient of the Botanical Society Award for Young Scientists, 1990.     

Dynamics of cell wall structure in Saccharomyces cerevisiae

The cell wall of Saccharomyces cerevisiae is an elastic structure that provides osmotic and physical protection and determines the shape of the cell. The inner layer of the wall is largely responsible for the mechanical strength of the wall and also provides the attachment sites for the proteins that form the outer layer of the wall. Here we find among others the sexual agglutinins and the flocculins. The outer protein layer also limits the permeability of the cell wall, thus shielding the plasma membrane from attack by foreign enzymes and membrane-perturbing compounds. The main features of the molecular organization of the yeast cell wall are now known. Importantly, the molecular composition and organization of the cell wall may vary considerably. For example, the incorporation of many cell wall proteins is temporally and spatially controlled and depends strongly on environmental conditions. Similarly, the formation of specific cell wall protein-polysaccharide complexes is strongly affected by external conditions. This points to a tight regulation of cell wall construction. Indeed, all five mitogen-activated protein kinase pathways in bakers' yeast affect the cell wall, and additional cell wall-related signaling routes have been identified. Finally, some potential targets for new antifungal compounds related to cell wall construction are discussed.     

Cell wall analysis

The cell wall is a rigid structure essential for survival of the fungal cell. Because of its absence in mammalian cells, the cell wall is an attractive target for antifungal agents. Thus, for different reasons, it is important to know how the cell wall is synthesized and how different molecules regulate that synthesis. The Schizosaccharomyces pombe cell wall is mainly formed by glucose polysaccharides and some galactomannoproteins. Here, we describe a fast and reliable method to analyze changes in S. pombe cell wall composition by using specific enzymatic degradation and chemical treatment of purified cell walls. This approach provides a powerful means to analyze changes in (1,3)beta-glucan and (1,3)alpha-glucan, two main polysaccharides present in fungal cell walls. Analysis of cell wall polymers will be useful to search for new antifungal drugs that may inhibit cell wall biosynthesis and/or alter cell wall structure.     

Regeneration and maturation of daughter cell walls in the autospore-forming green alga<Emphasis Type="Italic"> Chlorella vulgaris</Emphasis> (Chlorophyta,Trebouxiophyceae)

Cell-wall synthesis in Chlorella vulgaris, an autospore-forming alga, was observed using the cell wall-specific fluorescent dye Fluostain I. The observation suggested two clearly distinguishable stages in cell-wall synthesis: moderate synthesis during the cell-growth process and rapid synthesis at the cell-division stage. We used electron microscopy to examine the structural changes that occurred with growth in the premature daughter cell wall during the cell-growth and cell-division phases. The cell began to synthesize a new daughter cell wall shortly after its release from the autosporangium. A very thin daughter cell wall, with a thickness of about 2 nm, was formed inside the mother cell wall and completely enveloped the outer surface of the plasma membrane of the cell. The daughter cell wall gradually increased in thickness from 2 to 3.8 nm. During the protoplast-division phase in the cell-division stage, the daughter cell wall expanded on the surface of the invaginating plasma membrane of the cleavage furrow, accompanied by active synthesis of the cell wall, which increased in thickness from 3.8 to 6.1 nm. The daughter cell matured into an autospore while completely enclosed by its own thickening (from 6.1 to 17 nm) wall. Finally, the released daughter cell was enclosed by its own cell wall after the mother cell wall burst. The daughter cell with mature wall thickness (17–21 nm) emerged as a small, but complete, autospore.     

The plant cell wall: Biosynthesis,construction, and functions

The plant cell wall is composed of multiple biopolymers, representing one of the most complex structural networks in nature. Hundreds of genes are involved in building such a natural masterpiece. However, the plant cell wall is the least understood cellular structure in plants. Due to great progress in plant functional genomics,manyachievementshavebeenmadein uncovering cell wall biosynthesis, assembly, and architecture, as well as cell wall regulation and signaling. Such information has significantly advanced our understanding of the roles of the cell wall in many biological and physiological processes and has enhanced our utilization of cell wall materials. The use of cutting-edge technologies such as single-molecule imaging,nuclear magnetic resonance spectroscopy, and atomic force microscopy has provided much insight into the plant cell wall as an intricate nanoscale network, opening up unprecedented possibilities for cell wall research. In this review,we summarize the major advances made in understanding the cell wall in this era of functional genomics, including the latest findings on the biosynthesis, construction, and functions of the cell wall.     

Lipid and cell wall changes in an inositol-requiring mutant of Neurospora crassa.

An inositol deficiency in the inositol-requiring (inl) mutant of Neurospora crassa led to changes in the composition of the inositol-containing lipids and the cell wall. On deficient levels of inositol, phosphatidyl inositol decreased by 23-fold, di(inositolphosphoryl) ceramide decreased by 4-fold, and monoinositolphosphoryl ceramide increased slightly. The inositol deficiency also led to an aberrant hyphal morphology and changes in both the amount of cell wall and the amino sugar content of the cell wall. The glucosamine content of the cell wall decreased by 50%, the galactosamine increased by 50%, but no significant changes were found in the content of the cell wall amino sugar precursors, or in the amino acid, glucose, or total hexose content of the cell wall. Inositol-containing compounds were found associated with purified cell wall material. These compounds were bound tightly to the cell wall but could be removed by treatment with alkali, a treatment which disrupts the cell wall integrity. Possible mechanisms of how changes in lipid composition can affect cell wall biosynthesis are discussed.     

FINE-STRUCTURAL STUDY ON THE FORMATION OF THE GENERATIVE CELL WALL AND INTINE-3 LAYER IN A GROWING POLLEN GRAIN OF LILIUM LONGIFLORUM

At the end of mitosis in the lily pollen microspore, the fan-shaped cell plate gives rise to a cell wall delineating a hemispherical cell. At first, the cell wall of the newly formed generative cell and the intine-3 layer of the pollen grain wall are inseparable. Gradually, the wall of the generative cell near the pollen grain wall becomes thicker and wall segments are formed between the thickened zones, and these make a network system by which the generative cell becomes suspended and separated from the pollen grain wall. After the separation, the intine-3 layer is formed inside the intine 2. The generative cell wall and the intine-3 layer are formed by coated vesicles, polysaccharide particles and rough ER.     

产朊假丝酵母细胞壁33 ku蛋白的功能研究

通过胰蛋白酶和枯草杆菌蛋白酶对产朊假丝酵母Candida utilis细胞壁的酶解,发现一种分子质量为33 ku的酵母细胞壁主要结构蛋白. 研究显示,在细胞壁上这种蛋白质与细胞壁绝大多数蛋白质成分不同, 它不被胰蛋白酶水解,但对枯草杆菌蛋白酶的作用敏感.33 ku蛋白存在于酵母菌整个对数生长期的细胞壁中,特别是在对数早期细胞壁中,它是唯一的对胰蛋白酶作用不敏感的蛋白质成分.实验证明,该蛋白质对维系酵母细胞壁骨架成分葡聚糖的相互连接和细胞壁的完整结构,具有重要作用,是一种重要的酵母细胞壁嵌合蛋白.     

Regulation of cell wall biogenesis in Saccharomyces cerevisiae: the cell wall integrity signaling pathway

The yeast cell wall is a strong, but elastic, structure that is essential not only for the maintenance of cell shape and integrity, but also for progression through the cell cycle. During growth and morphogenesis, and in response to environmental challenges, the cell wall is remodeled in a highly regulated and polarized manner, a process that is principally under the control of the cell wall integrity (CWI) signaling pathway. This pathway transmits wall stress signals from the cell surface to the Rho1 GTPase, which mobilizes a physiologic response through a variety of effectors. Activation of CWI signaling regulates the production of various carbohydrate polymers of the cell wall, as well as their polarized delivery to the site of cell wall remodeling. This review article centers on CWI signaling in Saccharomyces cerevisiae through the cell cycle and in response to cell wall stress. The interface of this signaling pathway with other pathways that contribute to the maintenance of cell wall integrity is also discussed.     

Expansive growth of plant cell walls.

The enlargement of plant cell walls is a key determinant of plant morphogenesis. Current models of the cell wall are reviewed with respect to their ability to account for the mechanism of cell wall enlargement. The concept of primary and secondary wall loosening agents is presented, and the possible roles of expansins, xyloglucan endotransglycosylase, endo-1,4-beta-D-glucanase, and wall synthesis in the process of cell wall enlargement are reviewed and critically evaluated. Experimental results indicate that cell wall enlargement may be regulated at many levels.     

Presence of a mannoprotein, MnpAp, in the hyphal cell wall of Aspergillus nidulans

The presence of a mannoprotein, MnpAp, in the hyphal cell wall of Aspergillus nidulans was examined by immunogold electron microscopy using a mnpA-null mutant as a negative control. The hyphal cell wall of wild type consisted of two layers-an electron-dense smooth outer layer and an electron-translucent inner layer-while the hyphal cell wall of the mnpA-null mutant had an electron-dense irregular outer layer together with the electron-translucent inner layer. In wild type, MnpAp was present throughout the electron-translucent layer of the hyphal cell wall but was absent from the conidial cell wall. In the mnpA-null mutant, MnpAp was absent from the cell walls of both cell types. These results indicate that MnpAp is present in the hyphal cell wall and that it influences cell wall surface structure.     

Trifluoromethanesulfonic acid-based proteomic analysis of cell wall and secreted proteins of the ascomycetous fungi Neurospora crassa and Candida albicans

Cell wall proteins from purified Candida albicans and Neurospora crassa cell walls were released using trifluoromethanesulfonic acid (TFMS) which cleaves the cell wall glucan/chitin matrix and deglycosylates the proteins. The cell wall proteins were then characterized by SDS–PAGE and identified by proteomic analysis. The analyses for C. albicans identified 15 cell wall proteins and six secreted proteins. For N. crassa, the analyses identified 26 cell wall proteins and nine secreted proteins. Most of the C. albicans cell wall proteins are found in the cell walls of both yeast and hyphae cells, but some cell type-specific cell wall proteins were observed. The analyses showed that the pattern of cell wall proteins present in N. crassa vegetative hyphae and conidia (asexual spores) are quite different. Almost all of the cell wall proteins identified in N. crassa have close homologs in the sequenced fungal genomes, suggesting that these proteins have important conserved functions within the cell wall.     

The role of cell wall in plant embryogenesis

This review presents recent data about cell wall involvement in plant embryogenesis. During plant development, the cell wall is subjected to precise regulation. During this process a bidirectional information exchange between the cell wall and the protoplast is observed. The cell wall also mediates in the cell-cell (apoplastic) and cell to cell (symplastic) information flow. Especially some products derived from the hydrolysis of specific cell wall compounds can act as short distance signal transduction molecules during the development. Oligosaccharins are a group of such products. Their activity and sources focused the researchers' attention on the biochemical composition of the cell wall and the activity of some cell wall enzymes. The dramatic influence on the embryo body shape has also the cell wall synthesis machinery, including vesicular secretion pathways. Moreover, the interplay between the turgor pressure and counteracting cell walls and neighbouring cells (in higher organisms) creates the specific mechanical forces influencing the development of the whole plant. We conclude that discovering factors which can influence cell wall physiology and architecture is crucial for a better understanding of plant embryogenesis. In this review we summarize some recent experimental data reporting plant cell wall involvement in embryogenesis, putting special emphasis on somatic embryogenesis.     

Extensibility of isolated cell walls in the giant tip-growing cells of the xanthophycean alga Vaucheria terrestris

Apical cell wall fragments isolated from the giant-cellular xanthophycean alga Vaucheria terrestris sensu Götz were inflated with silicone oil by applying internal pressure ranging from 0.1 to 0.7 MPa, and the time-course of cell wall deformation was recorded and analyzed by videomicroscopy. Cell wall extensibility in the tip-growing region was estimated by the pressure required for cell wall extension, the amount of total extension until cell wall rupture and the rate of cell wall extension. Apical cell walls exhibited gradual extension, or creep, during inflation, which was eventually followed by rupture at the apical portion, whereas no appreciable extension was found in the cylindrical basal portion of the cell wall fragment. Besides the largest extension observed around the tip, substantial extension was also observed along the subapical region of the cell wall. The wall extensibility was dependent on the buffer pH used for infiltration before inflation. The optimum pH for the extension was about 8.0, but the cell wall was much less extensible after infiltration with an acidic buffer. Cell wall extensibility was dependent on the pH of the buffer used before inflation, regardless of that used in the previous infiltration. Moreover, pretreatment of the cell wall with a protease caused considerable loosening of cell walls, but affected the pH dependence of cell wall extensibility little. These results indicate that the extensibility of the cell walls in the giant tip-growing cells of the alga is distinct from that of plant cells that exhibit "acid growth" in its dependence on environmental pH and the role of cell wall proteins.     

Differential histone modification and protein expression associated with cell wall removal and regeneration in rice (Oryza sativa)

The cell wall is a critical extracellular structure that provides protection and structural support in plant cells. To study the biological function of the cell wall and the regulation of cell wall resynthesis, we examined cellular responses to enzymatic removal of the cell wall in rice (Oryza sativa) suspension cells using proteomic approaches. We find that removal of cell wall stimulates cell wall synthesis from multiple sites in protoplasts instead of from a single site as in cytokinesis. Nucleus DAPI stain and MNase digestion further show that removal of the cell wall is concomitant with substantial chromatin reorganization. Histone post-translational modification studies using both Western blots and isotope labeling assisted quantitative mass spectrometry analyses reveal that substantial histone modification changes, particularly H3K18(AC) and H3K23(AC), are associated with the removal and regeneration of the cell wall. Label-free quantitative proteome analyses further reveal that chromatin associated proteins undergo dramatic changes upon removal of the cell wall, along with cytoskeleton, cell wall metabolism, and stress-response proteins. This study demonstrates that cell wall removal is associated with substantial chromatin change and may lead to stimulation of cell wall synthesis using a novel mechanism.     

GLYCOPROTEIN MOIETY IN THE CELL WALL OF THE RED MICROALGA PORPHYRIDIUM SP. (RHODOPHYTA) AS THE BIORECOGNITION SITE FOR THE CRYPTHECODINIUM COHNII-LIKE DINOFLAGELLATE

The Crypthecodinium cohnii -like heterotrophic dinoflagellate preys on the cells of the red microalga Porphyridium sp. UTEX 637, and not on other microalgae. The dinoflagellate contains enzymes that degrade the cell wall complex of this species of alga and not that of other red microalgae. The cells of the red microalgae are encapsulated within a cell wall complex composed of about 10 sugars, sulfate, and proteins. We previously hypothesized that the dinoflagellate recognizes the cell wall of this alga. In this study, we have shown that the biorecognition site is the 66-kDa glycoprotein in the algal cell wall complex. The methodology used in this study was based on changing the algal cell wall composition and examining the prey and chemosensory response of the dinoflagellate. The dinoflagellate was not attracted to the cell wall of other red microalgae, which are similar to that of Porphyridium sp., or to sugars composing its cell wall. However, the dinoflagellate preyed on and was attracted to Porphyridium sp. mutants (DCB resistant) having modified cell wall polysaccharide composition, probably because the 66-kDa cell wall glycoprotein was not changed. The dinoflagellate did not respond chemotactically to enzymatically degraded cell wall complex. Treatment of the cell wall complex with antiserum to the 66-kDa glycoprotein or with the lectin concanavalin A (con A), which binds specifically to α-d-mannosyl and α-d-glucosyl residues, did not affect the chemotactic attraction. However, prey by the dinoflagellate was prevented when the algal cells were blocked with antiserum specific to the 66-kDa glycoprotein or with con A. These latter results provide direct proof that the 66-kDa cell wall glycoprotein isthe recognition site and prey-prevention results from the blocking of this site on the cell wall.     

CELL WALL STRUCTURE AND IRON DISTRIBUTION IN THE GREEN ALGA STAURASTRUM LUETKEMUELLERI (DESMIDIACEAE)1

The cell wall of Staurastrum luetkemuelleri Donnat & Ruttner was examined with scanning electron microscope (SEM) using whole cells, in thin sections with transmission electron microscope (TEM), and in air dried whole cells and unstained thin sections with X-ray microanalysis in the scanning-transmission electron microscope (STEM). The cell wall was ornamented with spines and wartlike structures. Spines were solid structures, consisting of deposits of cell wall material between two main cell wall layers. The wart-like structures were pore organs extending through the cell wall and the mucilaginous layer outside the cell wall. The pore cylinder was surrounded by deposits of cell wall material similar to the ones in the spines. X-ray microanalysis of selected areas on whole cells from a natural population showed iron accumulation in discrete locations on the cell extensions of S. luetkemuelleri. In the unstained thin sections iron was found only in the cell wall deposits in the spines. Cells grown in laboratory cultures failed to show iron accumulation regardless of readdition of iron-EDTA (Fe-EDTA) to the culture medium.