Stages Of Cell Wall Formation Research Articles

Anomalies in the valve morphogenesis of the centric diatom alga Aulacoseira islandica caused by microtubule inhibitors.

ABSTRACTOf all unicellular organisms possessing a cell wall, diatoms are the most adept at micro- and nanoscale embellishment of their frustules. Elements of their cell walls are formed inside the cell under cytoskeletal control. In this work, we used laser scanning microscopy and electron microscopy to describe the major stages of cell wall formation in the centric diatom algae Aulacoseira islandica and to study the effect of various microtubule inhibitors on the morphogenesis of frustule elements. Our results show that colchicine inhibits karyokinesis and cytokinesis in A. islandica colonies. In contrast, valve morphogenesis is changed, rather than inhibited altogether. In normal cells, this process starts simultaneously in both daughter cells, beginning with the formation of two adjacent discs that later become valve faces and connecting spines. Under colchicine treatment, however, the cleavage furrow is blocked and a single lateral valve forms on the side of the cylindrical frustule. As a result, a single hollow pipe forms instead of two separate drinking glass-shaped frustules; such pipes can form up to 35% of all forming frustules. Colchicine inhibits the formation of connecting spines, whereas paclitaxel causes spines to form a complex, branching shape. At the same time, inhibitors do not affect the formation of areolae (openings) in the frustule. We discuss the possibility that various processes of the diatom frustule morphogenesis are controlled by two different mechanisms: membrane-related micromorphogenesis and cytoskeleton-mediated macromorphogenesis.

Lignification in developing culms of bamboo Sinobambusa tootsik

Bamboos are among the largest woody grasses and grow very rapidly. Although lignin is a crucial factor for the utilization of bamboo biomass, the lignification mechanism of bamboo shoots is poorly understood. We studied lignification in the bamboo Sinobambusa tootsik during culm development. Elongation growth began in May and ended in late-June, when the lignin content was approximately half that in mature culms. Thioacidolysis analysis indicated that p-hydroxyphenyl units in lignin formed even at late stages of lignification. The syringyl/guaiacyl ratio varied during culm development. Various lignin precursors were detected in developing culms by liquid chromatography–mass spectrometry. The ferulic acid content decreased from May to June, indicating that ferulic acid was utilized in early stages of cell wall formation. Monolignol glucosides were detected at early stages of lignification, whereas the contents of monolignols, coniferaldehyde, sinapaldehyde, p-coumaric acid, and ferulic acid peaked at later stages of lignification. Therefore, lignin precursors may be supplied differentially during the lignification process. In August, the rate of lignification decreased, although the contents of various lignin precursors peaked, implying that the rate-limiting step in the cessation of lignification in bamboo is transport or polymerization of lignin precursors, rather than their biosynthesis.

Activity of selected hydrolytic enzymes in Allium sativum L. anthers

The aim of the study was to determine enzymatic activity in sterile Allium sativum anthers in the final stages of male gametophyte development (the stages of tetrads and free microspores). The analysed enzymes were shown to occur in the form of numerous isoforms. In the tetrad stage, esterase activity was predominant, which was manifested by the greater number of isoforms of the enzyme. In turn, in the microspore stage, higher numbers of isoforms of acid phosphatases and proteases were detected. The development of sterile pollen grains in garlic is associated with a high level of protease and acid phosphatase activity and lower level of esterase activities in the anther locule. Probably this is the first description of the enzymes activity (ACPH, EST, PRO) in the consecutives stages of cell wall formation which is considered to be one of the causes of male sterility in flowering plant.

Lignin masks the presence of fibrillar network structure in the cell corner middle lamella (CCML)

Abstract The presence of fibrillar structures (FS) in the cell corner middle lamella (CCML) regions was demonstrated in several species of plants. The FS in the CCML of bass wood, oak wood, and bamboo became clearly visible after removal of lignin by wood decay fungi. The occurrence of FS in the CCML was also confirmed by examining early stages of cell wall formation in silver poplar, Japanese red pine, Arabidopsis and alfalfa. The fibrillar texture became increasingly less defined with the onset of lignification as the interfibrillar spaces were masked by lignin polymers and the fibrillar network became embedded within the lignin matrix. The FS stained positively with PATAg and ruthenium red, which is interpreted to be an indicator of the presence of structural polysaccharides (non-cellulosics and pectins). Our work demonstrated that fibrillar network is a characteristic feature of CCML of plant cell walls that is clearly visible prior to lignification of this cell wall region, but becomes invisible after the deposition of lignin.

Proposed supramolecular structure of lignin in softwood tracheid compound middle lamella regions

Abstract The structure of lignin in the compound middle lamella (CML) of softwood tracheids differs from that in the secondary wall (SW) in regard to the content of condensed structures (5-5′-biphenyl, dibenzodioxocin and 4-O-5′-diphenyl ether). In an early stage of cell wall formation, random coarse networks composed of thin cellulose microfibrils (CMFs), hemicelluloses, and pectin are formed in the CML, then globular p-hydroxyphenyl/guaiacyl lignin (HG-lignin) is deposited quickly into the network. The globular lignin is assumed to be a micellar aggregate of oligolignols folded at the β-O-4 bond with their phenolic ends on the outer part of the aggregate. When 3D clusters of the globules are deposited on the preformed network of polysaccharides, further growth of the oligolignols by endwise addition of new monolignols is spatially limited, so frequent condensation occurs between growing aromatic ends of adjacent HG-oligolignols within the globule and between the wide contact boundaries of the 3D clustered globules to produce a highly condensed supramolecule in CML. In SW, the folded G-oligolignols are deposited slowly in the narrow tubular space surrounding thick CMFs coated with hemicelluloses. Condensation occurs mostly between adjacent growing ends of the oligolignols within the tubular aggregates. Spatial regulation of condensation of folded polylignols is one of the factors producing a different supramolecular structure for CML lignin than for SW lignin.

Immunolocalization and structural variations of xylan in differentiating earlywood tracheid cell walls of Cryptomeria japonica

We investigated the spatial and temporal distribution of xylans in the cell walls of differentiating earlywood tracheids of Cryptomeria japonica using two different types of monoclonal antibodies (LM10 and LM11) combined with immunomicroscopy. Xylans were first deposited in the corner of the S(1) layer in the early stages of S(1) formation in tracheids. Cell corner middle lamella also showed strong xylan labeling from the early stage of cell wall formation. During secondary cell wall formation, the innermost layer and the boundary between the S(1) and S(2) layers (S(1)/S(2) region) showed weaker labeling than other parts of the cell wall. However, mature tracheids had an almost uniform distribution of xylans throughout the entire cell wall. Xylan localization labeled with LM10 antibody was stronger in the outer S(2) layer than in the inner layer, whereas xylans labeled with LM11 antibody were almost uniformly distributed in the S(2) layer. In addition, the LM10 antibody showed almost no xylan labeling in the S(1)/S(2) region, whereas the LM11 antibody revealed strong xylan labeling in the S(1)/S(2) region. These findings suggest that structurally different types of xylans may be deposited in the tracheid cell wall depending on the developmental stage of, or location in, the cell wall. Our study also indicates that deposition of xylans in the early stages of tracheid cell wall formation may be spatially consistent with the early stage of lignin deposition in the tracheid cell wall.

Cell wall secretion in the green alga micrasterias.

The monoclonal antibodies JIM 1 against non-arabinogalactan epitopes, JIM 5 and JIM 7 recognizing unesterified and methyl-esterified pectins, and JIM 8 specific for arabinogalactan proteins (AGPs) are used for investigating different stages of cell wall formation in high pressure frozen and freeze substituted Micrasterias cells by means of immunoelectron microscopy. The results show that the septum-forming vesicles and the septum wall consist mainly of methyl-esterified pectins which become only partly de-esterified in the septum wall. Arabinogalactan proteins appear at the septum rim at the end of septum growth and are main constituents of the primary cell wall, together with esterified pectins. Only the outermost layer of the primary cell wall is labelled by JIM 5, indicating the presence of unesterified pectins. AGPs, non-AGP epitopes indicated by JIM 1, and pectins are transported together in the contents of the primary wall, forming 'dark vesicles' from the site of their production at the dictyosomes to the plasma membrane. Labelling of exclusively the plasma membrane of the non-growing semicell by JIM 1 and JIM 8 points towards a regulatory mechanism of membrane glycoproteins for vesicle fusion. The secondary cell wall of Micrasterias is not labelled by any of the antibodies used. JIM 4, JIM 15, JIM 84 and MAC 207 do not produce any specific staining in Micrasterias.

A transglutaminase immunologically related to tissue transglutaminase catalyzes cross-linking of cell wall proteins in Chlamydomonas reinhardtii.

The addition of primary amines to the growth medium of the unicellular green alga Chlamydomonas reinhardtii disrupts cell wall assembly in both vegetative and zygotic cells. Primary amines are competitive inhibitors of the protein-cross-linking activity of transglutaminases. Two independent assays for transglutaminase confirmed a burst of extracellular activity during the early stages of cell wall formation in both vegetative cells and zygotes. When non-inhibiting levels of a radioactive primary amine ((14)C-putrescine) were added to the growth medium, both cell types were labeled in a reaction catalyzed by extracellular transglutaminase. The radioactive label was found specifically in the cell wall proteins of both cell types, and acid hydrolysis of the labeled material released unmodified (14)C-putrescine. Western blots of the proteins secreted at the times of maximal transglutaminase activity in both cell types revealed a single highly cross-reactive 72-kD band when screened with antibodies to guinea pig tissue transglutaminase. Furthermore, the proteins immunoprecipitated by this antiserum in vivo exhibited transglutaminase activity. We propose that this transglutaminase is responsible for an early cell wall protein cross-linking event that temporally precedes the oxidative cross-linking mediated by extracellular peroxidases.

Involvement of JIM13- and JIM8-Responsive Carbohydrate Epitopes in Early Stages of Cell Wall Formation

L.). The spatial and temporal expression of both antigens was studied in suspension cells used as the source-tissue for protoplast isolation, in suspension- and mesophyll-derived protoplasts, and in cells which developed from both types of protoplast. Immunofluorescence and immunocytochemical-electron microscopic methods revealed that labeling was present in the cell walls of most suspension cells and also in the incipients of cell walls synthesized around the protoplasts. This signal became much more intense as rebuilding of the cell wall progressed during culture. Relatively weaker labeling was observed in the cytoplasm, where it was frequently associated with the vacuolar compartment. Signal intensity varied between individual cells of the same population and in successive stages of development, but was always stronger with JIM13 than with JIM8. The role of JIM13-responsive epitope in the development of suspension-derived protoplasts was further studied by its ability to bind antibody added to cultures of different ages. Both JIM8- and JIM13-responsive epitopes were widespread in sugar beet cells of different origin and stage of cell wall synthesis. These epitopes may play an important role in cell wall formation and growth under in vitro conditions.

Changes in the arrangement of cellulose microfibrils associated with the cessation of cell expansion in tracheids

The relationship between the cessation of cell expansion and formation of the secondary wall was investigated in the early-wood tracheids of Abies sachalinensis Masters by image analysis and field emission scanning electron microscopy. The area of the lumen and the length of the perimeter of the lumen of differentiating tracheids increased from the cambium towards the xylem. These increases had just ceased in the case of tracheids closest to the cambium in which birefringence was first detected by observations with a polarizing light microscope. Cellulose microfibrils (MFs) deposited on the innermost surfaces of radial walls were not well ordered during the expansion of cells, but well ordered MFs were deposited at the subsequent stage of cell wall formation. The first well ordered MFs were oriented in an S-helix. The well ordered MFs had already been deposited at the tracheids where birefringence was first detected under the polarizing light microscope. These results indicate that the deposition of the well ordered MFs, namely, the formation of the secondary wall, begins before the cessation of cell expansion of tracheids. Therefore, it seems that the expansion of tracheids is restricted by the deposition of the secondary wall because the cell walls become rigid simultaneously with the development of the secondary wall and, therefore, the yield point of cell walls exceeds the turgor pressure of the cell.

Role of fractal dimension in internal stress fields of Ni3Fe single crystals

In this paper, using the similarity method we have determined the fractal dimension of the dislocation structure of Ni3Fe single crystals in chaos and in the stage of cell wall formation. We have established that in chaos D=1.04, and at the walls D=1.08. For a linear dependence τ=τf+α·G·b·ρ1/2, the internal stresses increase by a factor of 1.1 in chaos and 1.22 in the cells, while the internal energy increases by a factor of 1.22 and 1.48 respectively. We discuss the mechanisms for roughening the dislocation structure.

Accumulation of cell wall hydroxyproline-rich glycoprotein mRNA is an early event in maize embryo cell differentiation.

The accumulation of the mRNA coding for a hydroxyproline-rich glycoprotein (HRGP), an abundant component of the wall from the cells of vegetative tissues, has been observed in maize embryo by in situ hybridization. The HRGP mRNA accumulates in the embryo axis and not in the scutellum and preferentially in dividing and provascular cells. The histone H4 mRNA is distributed in similar tissues but is restricted to defined groups of cells, indicating that these two gene products have a different steady-state level of accumulation during the cell cycle. The HRGP mRNA appears to be a useful marker for early formation of the vascular systems. The mRNA accumulation correlates in space and time with cells having a low content of cellulose in their walls, suggesting that the mRNA is produced in the early stages of cell wall formation before complete deposition of cellulose.

Heterogeneity in formation of lignin

The formation of lignin in the cell wall of compression wood of Pinus thunbergii was examined by selective radio-labeling of specific structural units in the lignin and visualization of the label in the different morphological regions by microautoradiography. Deposition of lignin in the tracheid cell wall of compression wood occurred in the order: p-hydroxyphenyl, guaiacyl and syringyl lignin, which is the same order as observed in normal wood. However, the period of lignification in the compression wood was quite different from those of normal and opposite woods. The p-hydroxyphenyl units were deposited mainly in the early stage of cell wall formation in compound middle lamella in normal and opposite woods, while in compression wood, they were formed in both the compound middle lamella and the secondary wall. The most intensive lignification was observed during the formation of the S2 layer, proceeding from the outer to inner S2 layers for a long period in compression wood. In the normal or opposite woods, in contrast, the lignification became active after formation of S3 had begun, then proceeded uniformly in the secondary wall and ended after a short period.

Heterogeneity in Formation of Lignin. XIII. Formation of p-Hydroxyphenyl Lignin in Various Hardwoods Visualized by Microautoradiography

Abstract The heterogeneous nature of hardwood lignin was shown by visualizing the deposition process of p-hydroxyphenyl (H) lignin in the differentiating xylem of magnolia, beech, lilac and poplar. When p-glucocoumaryl alcohol-[arom. ring-2-3H], an efficient precursor of H units in lignin, was administered to the differentiating xylem of these trees, radioactivity was incorporated in the compound middle lamella region of vessel and fiber cell walls. The deposition of H units occurs only in the early stage of cell wall formation when the outer layer of the secondary wall is formed. H lignin deposits mainly within pectic substances and hemicellulose gel to form a highly condensed structural moiety.

Cell plate development and delayed formation of the pectic middle lamella in root meristems

The first stages of cell wall formation were followed in the root meristems of maize and French bean. Most of the primary wall components (hemicellulose, cellulose and highly methylated pectins) were laid down simultaneously along the cell plate. During young cell wall maturation within the meristem itself, significant topochemical alterations, coupled with the addition of new polysaccharides, produced complete redistribution of wall material leading to the progressive appearance of a proper middle lamella. Thus the formation of a pectic middle lamella does not precede the deposition of primary walls. It is delayed until the new partition joins to the mother cell wall.

Cryoultramicrotomy of plant protoplasts

IntroductionNaked plant cells (protoplasts) have been used for the study of lectin binding to the plasma membrane, and of the initial stages of cell wall formation (2,3 and refs, therein). In this paper, I describe methods for the cryoultramicrotomy of plant protoplasts and give a general description of their ultrastructure. In addition, labelled lectins have been applied to cryo-sections to locate intracellular binding sites, and the superior resolution of the negatively stained cryo-sections has been applied to a preliminary study of cell wall fibril formation.Materials and MethodsProtoplasts were prepared from meristematic leaves of leek (Allium porrum) by enzymatic digestion (3). After washing, the cells were fixed in 1% glutaraldehyde in 0.55 M sorbitol and 1 mM CaCl2 buffered at pH 7.2 with 10 mM sodium cacodylate or HEPES. They were then washed (16 h) in 100 mM sodium cacodylate pH 7.2 and infused with 1 M sucrose in the same buffer for 3 h. A very concentrated suspension of the cells was mounted on a specimen holder and frozen in nitrogen slush (liquid nitrogen at its freezing point).

β-1,3-Glucans may be associated with cell plate formation during cytokinesis

Sections of young lateral-root meristems of corn seedlings and Jerusalem artichoke tuber slices treated to induce cell divisions were stained with aniline blue and examined by fluorescence microscopy. In both tissues intense yellow fluorescence, similar to that given by callose in sieve plates, was observed in cell plates of cells undergoing cytokinesis and in recently formed transverse cell walls of newly divided cells. Staining was found after both chemical fixation and rapid freezing and was removed by prior β-1,3-glucanase treatment. The staining was not present in older walls. The results suggest that a unique polysaccharide, probably a β-1,3-glucan, is associated with the early stages of cell wall formation in cytokinesis. The role and fate of the polysaccharide are unknown.