Advances in determination of polymer structure and in preservation of structure for electron microscopy provide the best view to date of how polysaccharides and structural proteins are organized into plant cell walls. The walls that form and partition dividing cells are modified chemically and structurally from the walls expanding to provide a cell with its functional form. In grasses, the chemical structure of the wall differs from that of all other flowering plant species that have been examined. Nevertheless, both types of wall must conform to the same physical laws. Cell expansion occurs via strictly regulated reorientation of each of the wall's components that first permits the wall to stretch in specific directions and then lock into final shape. This review integrates information on the chemical structure of individual polymers with data obtained from new techniques used to probe the arrangement of the polymers within the walls of individual cells. We provide structural models of two distinct types of walls in flowering plants consistent with the physical properties of the wall and its components.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-313X.1993.tb00007.x

Structural models of primary cell walls in flowering plants: consistency of molecular structure with the physical properties of the walls during growth

Resistant starch (RS) is starch and products of its small intestinal digestion that enter the large bowel. It occurs for various reasons including chemical structure, cooking of food, chemical modification, and food mastication. Human colonic bacteria ferment RS and nonstarch polysaccharides (NSP; major components of dietary fiber) to short-chain fatty acids (SCFA), mainly acetate, propionate, and butyrate. SCFA stimulate colonic blood flow and fluid and electrolyte uptake. Butyrate is a preferred substrate for colonocytes and appears to promote a normal phenotype in these cells. Fermentation of some RS types favors butyrate production. Measurement of colonic fermentation in humans is difficult, and indirect measures (e.g., fecal samples) or animal models have been used. Of the latter, rodents appear to be of limited value, and pigs or dogs are preferable. RS is less effective than NSP in stool bulking, but epidemiological data suggest that it is more protective against colorectal cancer, possibly via butyrate. RS is a prebiotic, but knowledge of its other interactions with the microflora is limited. The contribution of RS to fermentation and colonic physiology seems to be greater than that of NSP. However, the lack of a generally accepted analytical procedure that accommodates the major influences on RS means this is yet to be established.

Short-Chain Fatty Acids and Human Colonic Function: Roles of Resistant Starch and Nonstarch Polysaccharides

Pectins: structure, biosynthesis, and oligogalacturonide-related signaling.

The interaction of the direct dye Congo red with intact beta-D-glucans provides the basis for a rapid and sensitive assay system for bacterial strains possessing beta-(1 leads to 4),(1 leads to 3)-D-glucanohydrolase, beta-(1 leads to 4)-D-glucanohydrolase, and beta-(1 leads to 3)-D-glucanohydrolase activities. A close correspondence was observed between cellulolytic activity and beta-(1 leads to 4)-D-glucanohydrolase and beta-(1 leads to 4),(1 leads to 3)-D-glucanohydrolase activities in isolates from the bovine rumen. Many of these isolates also possessed beta-(1 leads to 3)-D-glucanohydrolase activity, and this characteristic may have taxonomic significance.

Use of Congo red-polysaccharide interactions in enumeration and characterization of cellulolytic bacteria from the bovine rumen.

Carbohydrate and lignin contents of plant materials used in animal feeding

A simple and rapid preparation of alditol acetates for monosaccharide analysis

An improved procedure for the methylation analysis of oligosaccharides and polysaccharides

Form and function of arabinogalactans and arabinogalactan-proteins

A characteristic feature of grasses and commercially important cereals is the presence of (1,3;1,4)-beta-d-glucans in their cell walls We have used comparative genomics to link a major quantitative trait locus for (1,3;1,4)-beta-d-glucan content in barley grain to a cluster of cellulose synthase-like CslF genes in rice After insertion of rice CslF genes into Arabidopsis, we detected (1,3;1,4)-beta-d-glucan in walls of transgenic plants using specific monoclonal antibodies and enzymatic analysis Because wild-type Arabidopsis does not contain CslF genes or have (1,3;1,4)-beta-d-glucans in its walls, these experiments provide direct, gain-of-function evidence for the participation of rice CslF genes in (1,3;1,4)-beta-d-glucan biosynthesis

https://science.sciencemag.org/content/sci/311/5769/1940.full.pdf

Cellulose Synthase-Like CslF Genes Mediate the Synthesis of Cell Wall (1,3;1,4)-ß-d-Glucans

Three structural classes of (1-->3)-beta-D-glucans are encountered in some important soil-dwelling, plant-associated or human pathogenic bacteria. Linear (1-->3)-beta-glucans and side-chain-branched (1-->3,1-->2)-beta-glucans are major constituents of capsular materials, with roles in bacterial aggregation, virulence and carbohydrate storage. Cyclic (1-->3,1-->6)-beta-glucans are predominantly periplasmic, serving in osmotic adaptation. Curdlan, the linear (1-->3)-beta-glucan from Agrobacterium, has unique rheological and thermal gelling properties, with applications in the food industry and other sectors. This review includes information on the structure, properties and molecular genetics of the bacterial (1-->3)-beta-glucans, together with an overview of the physiology and biotechnology of curdlan production and applications of this biopolymer and its derivatives.

Bruce A. Stone

Papers

A simple and rapid preparation of alditol acetates for monosaccharide analysis

An improved procedure for the methylation analysis of oligosaccharides and polysaccharides

Form and function of arabinogalactans and arabinogalactan-proteins

Cellulose Synthase-Like CslF Genes Mediate the Synthesis of Cell Wall (1,3;1,4)-ß-d-Glucans

Curdlan and other bacterial (1→3)-β-d-glucans