Plant cell-walls formation

Role of Microtubules in Cytokinesis and in Plant Cell Wall Formation... 

Fractionation and Chemistry of Citrus Pectic Polysaccharides. Pectic polysaccharides, commonly known as pectin, appear early in plant cell-wall formation. A series of complex biochemical steps results in the formation of cell plates followed first by its growth in area (primary cell wall) then in thickness (secondary cell wa.ll). Exclusive of randomly oriented cellulose fibrils, primary cell wall is composed mainly of pectic polysaccharides (34). These pectic polysaccharides are rich in D-galacturonic acid, D-galactose and L-arabinose residues. With growth in thickness of cell wall (secondary cell wall),there appears to be a replacement of pectic polysaccharide deposition with polysaccharides rich in D-glucuronic acid or 4-0-methyl-D-glucuronic acid,... 

Mulder B.M., Schel J.H.N., and Emons A.M.C. 2004. How the geometrical model for plant cell wall formation enables the production of a random texture. Cellulose 11 395-401. 

Herth W. 1985b. Plant cell wall formation. In Robards A.W. (ed.). Botanical Microscopy 1985. Oxford University Press, Oxford, pp. 285-310. 

Ice formation is both beneficial and detrimental. Benefits, which include the strengthening of food stmctures and the removal of free moisture, are often outweighed by deleterious effects that ice crystal formation may have on plant cell walls in fmits and vegetable products preserved by freezing. Ice crystal formation can result in partial dehydration of the tissue surrounding the ice crystal and the freeze concentration of potential reactants. Ice crystals mechanically dismpt cell stmctures and increase the concentration of cell electrolytes which can result in the chemical denaturation of proteins. Other quaHty losses can also occur (12). 

Submembranous microtubules are often present in parallel bundles beneath the plasma membrane in the cells of higher plants, particularly during cell wall formation (Hardham and Gimning, 1978). Circular submembranous bundles of microtubules are a feature of bird erythrocytes and mammalian blood platelets, where they maintain the discoid shape of these structures (Dustin, 1980). 

Neufeld, E.F., Feingold, D.S., and Hassid, W.Z. (1958) Enzymatic conversion of uridine diphosphate D-glucuronic acid to uridine diphosphate galacturonic acid, uridine diphosphate xylose, and uridine diphosphate arabinose. JAmer.Chem.Soc. 80 4430 Northcote, D.H. (1985) Control of cell wall formation during growth. In Biochemistry of Plant Cell Walls, edited by C.T. Brett, et al, pp. 177-197. Cambridge University Press, Cambridge. 

Milieu conditions in gastrointestinal tract can influence the pectin structure and properties. Under the acid conditions of the stomach (pH 2-4) extraction of pectin from plant cell walls and hydrolysis of side chains can occur. In small intestine (pH 5-6) -elimination of main chains or de-esterification seems to be possible. In caecum and colon (pH 6-8) a strong fermentation of pectin takes place causing depolymerization to oligomers and leading to formation of short chain fatty acids and gases. The presence of OligoGalA is not yet clarified. 

Vardi A, Formiggini F, Casotti R, De Martino A, Ribalet F, Miralto A, Bowler C (2006) A stress surveillance system based on calcium and nitric oxide in marine diatoms. PLoS Biol 4 411 119 Vorwerk S, Somerville S, Somerville C (2004) The role of plant cell wall polysaccharide composition in disease resistance. Trends Plant Sci 9 203-209 Vreeland V, Laetsch WM (1990) A gelling carbohydrate in algal cell wall formation. In Adair WS, Mecham RP (eds) Organization and assembly of plant and animal extracellular matrix. Academic, San Diego, CA, ppl 37—171... 

Plant cell walls are complex, heterogeneous structures composed mainly of polymers, such as cellulose, hemicelluloses, and lignins. In spite of several decades of research, cell wall assembly and the biosynthesis and ultimate biodegradative pathways of individual polymers are still far from being fully understood. One simple example will suffice Even today, no enzyme capable of catalyzing cellulose formation in vitro has been obtained. 

In animal structural proteins in vivo, the only known dimer of tyrosine is dityrosine (40,41) in the extensin of plant cell walls, in contrast, the only dimer formed in vivo is isodityrosine (16). How is the coupling of tyrosine in plants confined to the formation of isodityrosine There is nothing unique about the local environment of the tyrosine residues in (pure) extensin, since... 

Two factors associated with the plant cell wall were considered which might direct exclusive isodityrosine formation ... 

Evidence Against Cell Wall pH and Isoperoxidase Specificity as Determinants of Isodityrosine Formation. To test these possible explanations for the exclusive formation of isodityrosine in the plant cell wall, samples of [14C]tyrosine were oxidized by H2O2 in the presence of three sharply contrasting horseradish-isoperoxidases [two low-pi (acidic) and one high-pi (basic)] at a wide range of pH values (37). 

It may be concluded that neither pH nor isozyme-specificity is likely to direct the exclusive formation of isodityrosine in the plant cell wall in vivo. Indeed, it might be argued that isozyme-specificity is intrinsically unlikely to direct the orientation of coupling (dityrosine vs. isodityrosine) since the role of the enzyme is thought to be merely the production of tyrosine free radicals (44) which then non-enzymically pair off. 

Role of Neighboring Polysaccharide Molecules in Determining the Orientation of Tyrosine Residues During Coupling. These considerations suggest a third possible explanation for the exclusive formation of isodityrosine in the plant cell wall in vivo that the neighboring structural molecules of the wall constrain extensin to prevent dityrosine formation. This would mean that the biologically relevant substrate for peroxidase in the plant cell wall is not naked extensin but extensin complexed with another wall component, possibly an acidic polysaccharide to which the extensin would bind ionically. 

There are at least five types of phenylpropanoid related reactions which appear to occur in plant cell walls. Two are UV-mediated photochemical reactions, and hence may be restricted only to the first few layers of cells under the plant surface due to poor penetrability of the light (3). The other reactions appear to be enzymatically mediated, and result in the formation of dimers or polymers from the corresponding monomeric units. 

Attachment of Hydroxycinnamic Acids to Structural Cell Wall Polymers. Peroxidase mediation may also result in binding the hydroxycinnamic acids to the plant cell wall polymers (66,67). For example, it was reported that peroxidases isolated from the cell walls of Pinus elliottii catalyze the formation of alkali-stable linkages between [2-14C] ferulic acid 1 and pine cell walls (66). Presumably this is a consequence of free-radical coupling of the phenoxy radical species (from ferulic acid 1) with other free-radical moieties on the lignin polymer. There is some additional indirect support for this hypothesis, since we have established that E-ferulic acid 1 is a good substrate for horseradish peroxidase with an apparent Km (77 /tM), which is approximately one fifth of that for E-coniferyl alcohol (400 /iM) (unpublished data). 

Ferguson, L. R., Harris, P. J. (1998). Suberized plant cell walls suppress formation of heterocyclic amine-induced aberrant crypts in a rat model. Chem.-Biol. Interact., 114, 191-209. 

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