Exploration of cell wall architecture with the rapid-freeze deep-etch technique

1993 ◽  
Vol 51 ◽  
pp. 128-129
Author(s):  
Béatrice Satiat-Jeunemaitre ◽  
Chris Hawes
Keyword(s):  
Plant Cell ◽  
Cell Walls ◽  
Cell Biology ◽  
Molecular Model ◽  
Three Dimensional ◽  
Secretory Activity ◽  
Wall Structure ◽  
Specimen Preparation ◽  
Molecular Architecture ◽  
Plant Cell Walls

The comprehension of the molecular architecture of plant cell walls is one of the best examples in cell biology which illustrates how developments in microscopy have extended the frontiers of a topic. Indeed from the first electron microscope observation of cell walls it has become apparent that our understanding of wall structure has advanced hand in hand with improvements in the technology of specimen preparation for electron microscopy. Cell walls are sub-cellular compartments outside the peripheral plasma membrane, the construction of which depends on a complex cellular biosynthetic and secretory activity (1). They are composed of interwoven polymers, synthesised independently, which together perform a number of varied functions. Biochemical studies have provided us with much data on the varied molecular composition of plant cell walls. However, the detailed intermolecular relationships and the three dimensional arrangement of the polymers in situ remains a mystery. The difficulty in establishing a general molecular model for plant cell walls is also complicated by the vast diversity in wall composition among plant species.

Root hair cell walls: filling in the frameworkThis review is one of a selection of papers published in the Special Issue on Plant Cell Biology.

2006 ◽  
Vol 84 (4) ◽  
pp. 613-621 ◽  
Author(s):  
M.E. Galway
Keyword(s):  
Cell Wall ◽  
Hair Cell ◽  
Plant Cell ◽  
Root Hair ◽  
Cell Walls ◽  
Cell Biology ◽  
High Speed ◽  
Root Hairs ◽  
Experimental System ◽  
Plant Cell Walls

Rapid progress is being made in determining the composition, synthesis, and mechanical properties of plant cell walls. Although tip-growing root hairs provide an excellent example of high-speed cell wall assembly, they have been relatively neglected by researchers interested in cell walls and those interested in tip growth. This review aims to present the root hair as an experimental system for future cell wall studies by assembling recent discoveries about the walls onto the existing framework based on older information. Most recent data come from arabidopsis ( Arabidopsis thaliana (L.) Heynh) and model legumes. Evidence supporting the turgor-mediated expansion of hair cell walls is considered, along with a survey of three components needed for cell wall expansion without rupture: cellulose (the role of CesA cellulose synthases is also addressed), Csld3, a cellulose synthase-like protein, and Lrx1, a cell wall protein. Further clues about hair cell wall composition have been obtained from gene expression studies and the use of monoclonal antibodies. Finally, there is a review of the experimental evidence that (i) hairs near the hypocotyl differ developmentally and structurally from other hairs and (ii) biosynthesis of wall components in hairs may differ significantly from the epidermal cells that they grew from. All of these recent advances suggest that root hairs could provide valuable data to augment models of plant cell walls based on more conventional cell types.

Cell-wall studies in the Chlorophyceae l. A preliminary study of the effect of continuous illumina­tion on wall structure in Cladophora rupestris

1953 ◽  
Vol 141 (904) ◽  
pp. 407-419 ◽  
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Continuous Illumination ◽  
Fibrillar Structure ◽  
Wall Structure ◽  
Plant Cell Walls ◽  
X Ray ◽  
Polarization Optics ◽  
Preliminary Study

Cultures of Cladophora rupestris under continuous illumination, for periods up to six months, have shown that the wall structure is modified as compared with control cultures with more normal illumination. This has been demonstrated by means of X-ray analysis and by polarization optics, and supported by ancillary observations oh both cultures. Under continuous illumination transverse microfibrils are laid down much more abundantly than are the longitudinal microfibrils. This may form the first step towards an understanding of the genesis of the crossed fibrillar structure of plant cell walls.

Structural Polysaccharides In Molecular Architecture of Plant Cell Wallsfrom Algae to Hardwoods

1991 ◽  
Vol 255 ◽  
Author(s):  
R. H. Atalla ◽  
J. M. Hackney
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Higher Plants ◽  
Morphological Development ◽  
Molecular Architecture ◽  
Plant Cell Walls ◽  
Ordered Structures ◽  
Phylogenetic Framework ◽  
Wall Mass

AbstractThe structural polysaccharides are a family of polymers of hexoses and pentoses that occur in all plant cell walls. The distinguishing characteristic of these polymers is a β-1,4-linked backbone. The most common among these is cellulose, which is the linear homopolymer of anhydroglucose. These polysaccharides are capable of aggregating into highly ordered structures that are the primary determinants of the mechanical and physical properties of cell walls. An overview of the variations in patterns. of structural-polysaccharide aggregation within cell walls is presented here. Among the majority of the algae cellulose is the dominant structural polysaccharide; thus the habit of aggregation is dominated by the patterns of cellulose. Among primitive plants, other structural polysaccharides represent a larger fraction of cell-wall mass and cellulose is less dominant. In woody tissues of higher plants, structural polysaccharides are the major components of the cell wall, and the patterns of aggregation are again dominated by the characteristic habits of cellulose. Within tile phylogenetic framework, higher levels of morphological development apparently involve greater complexity in the molecular architecture of the cell walls and a finer level of blending of the components of aggregates at the molecular level.

KNAT7 regulates xylan biosynthesis in Arabidopsis seed-coat mucilage

2020 ◽  
Vol 71 (14) ◽  
pp. 4125-4139
Author(s):  
Yiping Wang ◽  
Yan Xu ◽  
Shengqiang Pei ◽  
Mingmin Lu ◽  
Yingzhen Kong ◽  
...  
Keyword(s):  
Plant Cell ◽  
Seed Coat ◽  
Cell Walls ◽  
Wall Structure ◽  
Plant Cell Walls ◽  
Arabidopsis Seed ◽  
Ideal System ◽  
Xylan Biosynthesis ◽  
Seed Coat Mucilage ◽  
Seed Mucilage

Abstract As a major hemicellulose component of plant cell walls, xylans play a determining role in maintaining the wall structure. However, the mechanisms of transcriptional regulation of xylan biosynthesis remain largely unknown. Arabidopsis seed mucilage represents an ideal system for studying polysaccharide biosynthesis and modifications of plant cell walls. Here, we identify KNOTTED ARABIDOPSIS THALIANA 7 (KNAT7) as a positive transcriptional regulator of xylan biosynthesis in seed mucilage. The xylan content was significantly reduced in the mucilage of the knat7-3 mutant and this was accompanied by significantly reduced expression of the xylan biosynthesis-related genes IRREGULAR XYLEM 14 (IRX14) and MUCILAGE MODIFIED 5/MUCILAGE-RELATED 21 (MUM5/MUCI21). Electrophoretic mobility shift assays, yeast one-hybrid assays, and chromatin immunoprecipitation with quantitative PCR verified the direct binding of KNAT7 to the KNOTTED1 (KN1) binding site [KBS,TGACAG(G/C)T] in the promoters of IRX7, IRX14, and MUM5/MUCI21 in vitro, in vivo, and in planta. Furthermore, KNAT7 directly activated the expression of IRX14 and MUM5/MUCI21 in transactivation assays in mesophyll protoplasts, and overexpression of IRX14 or MUM5/MUCI21 in knat7-3 partially rescued the defects in mucilage adherence. Taken together, our results indicate that KNAT7 positively regulates xylan biosynthesis in seed-coat mucilage via direct activation of the expression of IRX14 and MUM5/MUCI21.

Projected Structure of the Surface Protein of Sulfolobus Spec. B12 Determined to a Resolution of 1.0 NM by Cryo-Electronmicroscopy

1990 ◽  
Vol 48 (1) ◽  
pp. 102-103
Author(s):  
G. Lembcke ◽  
F. Zemlin
Keyword(s):  
Low Dose ◽  
Maximum Dose ◽  
Three Dimensional ◽  
Surface Protein ◽  
Protein S ◽  
Radiation Sensitivity ◽  
Specimen Preparation ◽  
Molecular Architecture ◽  
High Radiation ◽  
Fritz Haber

The thermoacidophilic archaebacterium Sulfolobus spec. B12 , which is closely related to Sulfolobus solfataricus , possesses a regularly arrayed surface protein (S-layer), which is linked to the plasma membrane via spacer elements spanning a distinct interspace of approximately 18 nm. The S-layer has p3-Symmetry and a lattice constant of 21 nm; three-dimensional reconstructions of negatively stained fragments yield a layer thickness of approximately 6-7 nm.For analysing the molecular architecture of Sulfolobus surface protein in greater detail we use aurothioglucose(ATG)-embedding for specimen preparation. Like glucose, ATG, is supposed to mimic the effect of water, but has the advantage of being less volatile. ATG has advantages over glucose when working with specimens composed exclusively of protein because of its higher density of 2.92 g cm-3. Because of its high radiation sensitivity electromicrographs has to be recorded under strict low-dose conditions. We have recorded electromicrographs with a liquid helium-cooled superconducting electron microscope (the socalled SULEIKA at the Fritz-Haber-lnstitut) with a specimen temperature of 4.5 K and with a maximum dose of 2000 e nm-2 avoiding any pre-irradiation of the specimen.

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