scholarly journals Unique lignin modifications pattern the nucleation of silica in sorghum endodermis

2020 ◽  
Vol 71 (21) ◽  
pp. 6818-6829 ◽  
Author(s):  
Nerya Zexer ◽  
Rivka Elbaum
Keyword(s):  
Cell Wall ◽  
Silicic Acid ◽  
Cell Walls ◽  
Dry Weight ◽  
Cell Wall Chemistry ◽  
Modified Lignin ◽  
Trace Concentrations ◽  
High Degree ◽  
Micrometer Scale ◽  
The Impact

Abstract Silicon dioxide in the form of hydrated silica is a component of plant tissues that can constitute several percent by dry weight in certain taxa. Nonetheless, the mechanism of plant silica formation is mostly unknown. Silicon (Si) is taken up from the soil by roots in the form of monosilicic acid molecules. The silicic acid is carried in the xylem and subsequently polymerizes in target sites to silica. In roots of sorghum (Sorghum bicolor), silica aggregates form in an orderly pattern along the inner tangential cell walls of endodermis cells. Using Raman microspectroscopy, autofluorescence, and scanning electron microscopy, we investigated the structure and composition of developing aggregates in roots of sorghum seedlings. Putative silica aggregation loci were identified in roots grown under Si starvation. These micrometer-scale spots were constructed of tightly packed modified lignin, and nucleated trace concentrations of silicic acid. Substantial variation in cell wall autofluorescence between Si+ and Si– roots demonstrated the impact of Si on cell wall chemistry. We propose that in Si– roots, the modified lignin cross-linked into the cell wall and lost its ability to nucleate silica. In Si+ roots, silica polymerized on the modified lignin and altered its structure. Our work demonstrates a high degree of control over lignin and silica deposition in cell walls.

Silica formation in sorghum (Sorghum bicolor) roots

2021 ◽  
Author(s):  
Nerya Zexer ◽  
Rivka Elbaum
Keyword(s):  
Cell Wall ◽  
Sorghum Bicolor ◽  
Silicic Acid ◽  
Cell Walls ◽  
Dry Weight ◽  
Soluble Form ◽  
Cell Wall Chemistry ◽  
Modified Lignin ◽  
Auto Fluorescence ◽  
The Impact

<p>Silicon oxides are the most abundant mineral group in soils. Therefore, plant roots are always exposed to some silicic acid (Si(OH)<sub>4</sub>), which is the soluble form of silicates. Monosilicic acid molecules are taken up by roots, carried in the xylem, and subsequently polymerize to silica in varied silicifying target sites. This biogenic silica (SiO<sub>2</sub>·<em>n</em>H<sub>2</sub>O) can constitute several percent by dry weight in certain plant taxa. However, the mechanisms of its formation remain mostly unknown. In the roots of sorghum (<em>Sorghum bicolor</em>), silica aggregates form in an orderly pattern along the cell walls of endodermis cells. To investigate the structure and composition of root silica aggregates, we studied their development along roots of hydroponically grown sorghum seedlings. By using Raman micro-spectroscopy, auto-fluorescence, and scanning electron microscopy, we found that putative silica aggregation loci could be identified in roots grown under Si starvation. These micrometer-scale spots were constructed of tightly packed modified lignin and were capable of nucleating trace concentrations of silicic acid. Substantial variation in cell wall auto-fluorescence between roots grown with and without silicic acid demonstrated the impact of silicon on cell wall chemistry. Taken together, this work demonstrates a high degree of control over lignin and silica deposition in cell walls. Such regulation implies an important, yet unknown, function for silicon in plant biology.</p>

scholarly journals Isolation and partial characterization of apiogalacturonans from the cell wall of Lemna minor

1970 ◽  
Vol 116 (4) ◽  
pp. 569-579 ◽  
Author(s):  
David A. Hart ◽  
Paul K. Kindel
Keyword(s):  
Cell Wall ◽  
Sodium Chloride ◽  
Cell Walls ◽  
Lemna Minor ◽  
Extraction Procedure ◽  
Ammonium Oxalate ◽  
Periodate Oxidation ◽  
Dry Weight ◽  
Weight Basis ◽  
Sephadex Column

1. A mild, reproducible extraction procedure, using 0.5% ammonium oxalate, was developed for the isolation of polysaccharides containing d-apiose from the cell wall of Lemna minor. On a dry-weight basis the polysaccharide fractions extracted with ammonium oxalate made up 14% of the material designated cell walls and contained 20% of the d-apiose originally present in the cell walls. The cell walls, as isolated, contained 83% of the d-apiose present in L. minor. 2. After extraction with ammonium oxalate, purified polysaccharides were obtained by DEAE-Sephadex column chromatography and by fractional precipitation with sodium chloride. With these procedures the material extracted at 22°C could be separated into at least five polysaccharides. On a dry-weight basis two of these polysaccharides made up more than 50% of the material extracted at 22°C. There was a direct relationship between the d-apiose content of the polysaccharides and their solubility in sodium chloride solutions; those of highest d-apiose content were most soluble. 3. All the polysaccharides isolated appeared to be of one general type, namely galacturonans to which were attached side chains containing d-apiose. The d-apiose content of the apiogalacturonans varied from 7.9 to 38.1%. The content of esterified d-galacturonic acid residues in all apiogalacturonans was low, being in the range 1.0–3.5%. Hydrolysis of a representative apiogalacturonan with dilute acid resulted in the complete removal of the d-apiose with little or no degradation of the galacturonan portion. 4. Treatment of polysaccharide fractions with pectinase established that those of high d-apiose content and soluble in m-sodium chloride were not degraded, whereas those of low d-apiose content and insoluble in m-sodium chloride were extensively degraded. When the d-apiose was removed from a typical pectinase-resistant polysaccharide, the remainder of the polysaccharide was readily degraded by this enzyme. 5. Periodate oxidation of representative polysaccharide fractions and apiogalacturonans and determination of the formaldehyde released showed that about 50% of the d-apiose molecules were substituted at either the 3- or the 3′-position.

scholarly journals Winter Nights during Summer Time: Stress Physiological Response to Ice and the Facilitation of Freezing Cytorrhysis by Elastic Cell Wall Components in the Leaves of a Nival Species

2020 ◽  
Vol 21 (19) ◽  
pp. 7042 ◽  
Author(s):  
Matthias Stegner ◽  
Barbara Lackner ◽  
Tanja Schäfernolte ◽  
Othmar Buchner ◽  
Nannan Xiao ◽  
...  
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Atmospheric Temperature ◽  
Cellular Level ◽  
Spongy Parenchyma ◽  
Mesophyll Cells ◽  
After Effects ◽  
Cell Wall Chemistry ◽  
Specific Tissue ◽  
Summer Time

Ranunculus glacialis grows and reproduces successfully, although the snow-free time period is short (2–3 months) and night frosts are frequent. At a nival site (3185 m a.s.l.), we disentangled the interplay between the atmospheric temperature, leaf temperatures, and leaf freezing frequency to assess the actual strain. For a comprehensive understanding, the freezing behavior from the whole plant to the leaf and cellular level and its physiological after-effects as well as cell wall chemistry were studied. The atmospheric temperatures did not mirror the leaf temperatures, which could be 9.3 °C lower. Leaf freezing occurred even when the air temperature was above 0 °C. Ice nucleation at on average −2.6 °C started usually independently in each leaf, as the shoot is deep-seated in unfrozen soil. All the mesophyll cells were subjected to freezing cytorrhysis. Huge ice masses formed in the intercellular spaces of the spongy parenchyma. After thawing, photosynthesis was unaffected regardless of whether ice had formed. The cell walls were pectin-rich and triglycerides occurred, particularly in the spongy parenchyma. At high elevations, atmospheric temperatures fail to predict plant freezing. Shoot burial prevents ice spreading, specific tissue architecture enables ice management, and the flexibility of cell walls allows recurrent freezing cytorrhysis. The peculiar patterning of triglycerides close to ice rewards further investigation.

Biodegradability of mature grass cell walls in relation to chemical composition and rumen microbial activity

1987 ◽  
Vol 108 (1) ◽  
pp. 201-209 ◽  
Author(s):  
C. W. Ford ◽  
R. Elliott
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Latin Square ◽  
Structural Features ◽  
Barley Straw ◽  
Grass Species ◽  
Tropical Species ◽  
Variable Degree ◽  
Cell Wall Constituent ◽  
Cell Wall Chemistry

SummaryCell walls from mature stems of three tropical grass species (Digitaria decumbens(pangola),Setaria anceps(cv. Kazangula) and sugar cane), and temperate barley straw, were analysed for lignin, carbohydrate, and the maj or acyl groups ferulate, ρ-coumarate and acetate. Samples were incubated in nylon bags in the rumen of sheep in a 4 x 4 latin-square design, and rates of disappearance of cellulose, hemicellulose, xylose, arabinose, ferulate, ρ-coumarate and acetate were determined during 60 h incubation. Interspecies differences in cell-wall chemistry appeared largely in the variable degree of acylation with p-coumaric acid (1·0–3·3%) and acetate (0·5–3·6%), and the high glucose concentration in the hemicellulose from pangola (17%) andSetaria(9%). Barley had much lower concentrations of these components than the tropical species. After 24 h incubation, losses of cellulose and acyl groups were greatest from pangola, whereas hemicellulose and its major components xylose and arabinose were degraded to the greatest degree from barley straw.Setariacell-wall components were generally more resistant to degradation than the other species. No relationship was found between the concentration of any cell-wall constituent and degradability measurements. Nor were changes in microbial population, indicated by measuring the accumulation of cystine on the fibres, related to the rate or degree of degradation of any of the measured cell-wall constituents. Lignin was fractionated with alkali into insoluble and soluble fractions. The latter (25–50% of original lignin) gave high interspecies correlations with the degradability of total hemicellulose and its component monosaccharides. It was concluded that variability in the biodegradability of the cell walls was more likely due toin situstructural features, such as cross-linking between polymers, than to the concentration of any particular cell-wall constituent.

scholarly journals Effects of Changes in Biopolymer Composition on Moisture in Acetylated Wood

Forests ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 719
Author(s):  
Tiantian Yang ◽  
Emil Engelund Thybring ◽  
Maria Fredriksson ◽  
Erni Ma ◽  
Jinzhen Cao ◽  
...  
Keyword(s):  
Cell Wall ◽  
Moisture Content ◽  
Spin Relaxation ◽  
Cell Walls ◽  
Lignin Content ◽  
Theoretical Estimate ◽  
Relaxation Times ◽  
Dry Weight ◽  
Hemicellulose Removal ◽  
Water Saturated

To investigate the effects of changes in biopolymer composition on moisture in acetylated poplar wood (Populus euramericana Cv.), the acetylation of control wood was compared to the acetylation of wood with reduced hemicellulose or lignin content (about 9% reduction of total specimen dry weight in both cases). Time-domain nuclear magnetic resonance relaxometry of water-saturated wood gave spin–spin relaxation times (T2) of water populations, while deuteration in a sorption balance was used to characterize the hydroxyl accessibility of the wood cell walls. As expected, the acetylation of pyridine-swelled wood reduced hydroxyl accessibility and made the cell wall less accessible to water, resulting in a reduction of cell wall moisture content by about 24% compared with control wood. Hemicellulose loss per se increased the spin–spin relaxation time of cell wall water, while delignification had the opposite effect. The combined effect of hemicellulose removal and acetylation caused more than a 30% decrease of cell wall moisture content when compared with control wood. The acetylated and partially delignified wood cell walls contained higher cell wall moisture content than acetylated wood. An approximate theoretical calculation of hydroxyl accessibility for acetylated wood was in the low range, but it agreed rather well with the measured accessibility, while acetylated and partially hemicellulose-depleted and partially delignified wood for unknown reasons resulted in substantially lower hydroxyl accessibilities than the theoretical estimate.

Composition and properties of the cell wall of Methanospirillum hungatii

1980 ◽  
Vol 26 (2) ◽  
pp. 115-120 ◽  
Author(s):  
G. D. Sprott ◽  
R. C. McKellar
Keyword(s):  
Amino Acids ◽  
Cell Wall ◽  
Cell Walls ◽  
Weight Fraction ◽  
Dry Weight ◽  
Wall Material ◽  
Bond Breaking ◽  
High Molecular Weight Fraction ◽  
Cell Wall Proteins ◽  
Isolated Cell

Dithiothreitol reacted, at pH 9.0, with the isolated cell walls of Methanospirillum hungatii, to release about 23% of the cell wall dry weight as a high molecular weight fraction (> 0.5 million daltons). Untreated walls consisted of 70% amino acids, 11% lipid, and 6.6% carbohydrate. Sugars were identified as rhamnose, ribose, glucose, galactose, and mannose. The wall material that was released contained only 47% amino acids and was enriched in lipid, glucose, and phosphate. These results support data from electron micrographs, showing the localized release of cell wall material by the disulfide bond-breaking reagent at alkaline pH. In amino acid composition the untreated walls did not differ greatly from the material released by dithiothreitol, but differed considerably from the walls of another strain of M. hungatii. The ratios of the amino acids found in the cell wall proteins of several archaebacteria and of Bacillus cereus spore coats were similar.

scholarly journals Glutamine synthetase encoded by glnA-1 is necessary for cell wall resistance and pathogenicity of Mycobacterium bovis

Microbiology ◽  
2010 ◽  
Vol 156 (12) ◽  
pp. 3669-3677 ◽  
Author(s):  
Harish Chandra ◽  
Seemi Farhat Basir ◽  
Manish Gupta ◽  
Nirupama Banerjee
Keyword(s):  
Cell Wall ◽  
Glutamine Synthetase ◽  
Mycobacterium Bovis ◽  
Mycobacterium Smegmatis ◽  
Cell Walls ◽  
Culture Medium ◽  
Wild Type Strain ◽  
Glutamine Supplementation ◽  
Antitubercular Drugs ◽  
Cell Wall Chemistry

Pathogenic strains of mycobacteria produce copious amounts of glutamine synthetase (GS) in the culture medium. The enzyme activity is linked to synthesis of poly-α-l-glutamine (PLG) in the cell walls. This study describes a glnA-1 mutant of Mycobacterium bovis that produces reduced levels of GS. The mutant was able to grow in enriched 7H9 medium without glutamine supplementation. The glnA-1 strain contained no detectable PLG in the cell walls and showed marked sensitivity to different chemical and physical stresses such as lysozyme, SDS and sonication. The sensitivity of the mutant to two antitubercular drugs, rifampicin and d-cycloserine, was also increased. The glnA-1 strain infected THP-1 cells with reduced efficiency and was also attenuated for growth in macrophages. A Mycobacterium smegmatis strain containing the M. bovis glnA-1 gene survived longer in THP-1 cells than the wild-type strain and also produced cell wall-associated PLG. The M. bovis mutant was not able to replicate in the organs of BALB/c mice and was cleared within 4–6 weeks of infection. Disruption of the glnA-1 gene adversely affected biofilm formation on polystyrene surfaces. The results of this study demonstrate that the absence of glnA-1 not only attenuates the pathogen but also affects cell surface properties by altering the cell wall chemistry of the organism via the synthesis of PLG; this may be a target for drug development.

scholarly journals Human serum triggers antibiotic tolerance in Staphylococcus aureus

2021 ◽  
Author(s):  
Elizabeth VK Ledger ◽  
Stéphane Mesnage ◽  
Andrew M Edwards
Keyword(s):  
Staphylococcus Aureus ◽  
Cell Wall ◽  
Human Serum ◽  
Bloodstream Infections ◽  
Two Component System ◽  
Membrane Target ◽  
Mrsa Strains ◽  
Induced Tolerance ◽  
High Degree ◽  
The Impact

Staphylococcus aureus is a frequent cause of bloodstream infections. Treatment can be challenging, even when isolates appear to be drug susceptible, with high rates of persistent and relapsing infection. This is particularly the case with infections caused by methicillin resistant S. aureus (MRSA) strains, which are resistant to frontline antibiotics. To understand how the host environment influences treatment outcomes in MRSA infections, we studied the impact of human serum on staphylococcal susceptibility to daptomycin, an antibiotic of last resort. This revealed that serum triggered a very high degree of tolerance to daptomycin, as well as several other classes of antibiotics and antimicrobial peptides, including gentamicin, nitrofurantoin, vancomycin, nisin and gramicidin. Serum-induced daptomycin tolerance was due to two independent mechanisms. Firstly, the host defence peptide LL-37 present in serum induced tolerance by triggering the staphylococcal GraRS two component system. This led to increased cell wall accumulation that reduced access of daptomycin to its membrane target. Secondly, GraRS-independent changes to the membrane resulted in increased cardiolipin abundance that also contributed to daptomycin tolerance. When both mechanisms were blocked, serum exposed S. aureus cells were as susceptible to daptomycin as bacteria growing in laboratory media. These data demonstrate that host factors can significantly modulate antibiotic susceptibility via diverse mechanisms, which may in turn contribute to treatment failure. The inhibition of serum-induced cell wall accumulation by fosfomycin reduced tolerance, suggesting that this antibiotic may form a useful combination therapy with daptomycin.

scholarly journals Molecular Weight and Degree of Methoxylation in Cell Wall Polyuronide during Softening in Pear and Apple Fruit

1992 ◽  
Vol 117 (4) ◽  
pp. 600-606 ◽  
Author(s):  
H. Yoshioka ◽  
K. Aoba ◽  
Y. Kashimura
Keyword(s):  
Molecular Weight ◽  
Cell Wall ◽  
Cell Walls ◽  
Soluble Fraction ◽  
Apple Fruit ◽  
Water Soluble ◽  
Pear Fruit ◽  
Water Soluble Fraction ◽  
High Degree ◽  
Soluble Fractions

The concentrations of water-soluble polyuronides in apples [Malus domestica Borkh.) and pears (Pyrus communis L.) increased, but those of EDTA- and HCl-soluble polyuronides decreased during softening. Total polyuronide content decreased slightly during softening in both fruits. Depolymerization of polyuronides was observed only in the water-soluble fraction in pear fruit during softening, concomitant with an increase in polygalacturonase (PG) activity. No detectable depolymerization was observed in any of the polyuronide fractions during softening of apple fruit nor was any PG activity detected. The polyuronide fractions extracted from pear and apple cell walls contained various amounts of methoxyl groups. Polyuronides with a high degree of methoxylation were preferentially lost from EDTA- and HCl-soluble polyuronides during softening of both fruit. The water-soluble polyuronide had a lower degree of methoxylation than those lost in the EDTA- and HCl-soluble fractions. These results suggest de-esterification of polyuronides with a high degree of methoxylation rather than the depolymerization of polyuronides in the solubilization of polyuronides during ripening of apples and pears.

Silicification of wood-cell walls

1994 ◽  
Vol 52 ◽  
pp. 428-429
Author(s):  
S. E. Keckler ◽  
D. M. Dabbs ◽  
N. Yao ◽  
I. A. Aksay
Keyword(s):  
Electron Microscopy ◽  
Cell Wall ◽  
Cell Walls ◽  
Lignin Content ◽  
Resin Composite ◽  
Middle Lamella ◽  
Cellulose Fibers ◽  
Complex Structures ◽  
Rich Region ◽  
Inorganic Precursors

Cellular organic structures such as wood can be used as scaffolds for the synthesis of complex structures of organic/ceramic nanocomposites. The wood cell is a fiber-reinforced resin composite of cellulose fibers in a lignin matrix. A single cell wall, containing several layers of different fiber orientations and lignin content, is separated from its neighboring wall by the middle lamella, a lignin-rich region. In order to achieve total mineralization, deposition on and in the cell wall must be achieved. Geological fossilization of wood occurs as permineralization (filling the void spaces with mineral) and petrifaction (mineralizing the cell wall as the organic component decays) through infiltration of wood with inorganics after growth. Conversely, living plants can incorporate inorganics into their cells and in some cases into the cell walls during growth. In a recent study, we mimicked geological fossilization by infiltrating inorganic precursors into wood cells in order to enhance the properties of wood. In the current work, we use electron microscopy to examine the structure of silica formed in the cell walls after infiltration of tetraethoxysilane (TEOS).

Sign in / Sign up

Export Citation Format

Share Document