Characterisation of extracellular polysaccharides from suspension cultures of members of the Poaceae

Abstract

Microscopic examination of suspension- cultured cells of Phleum pratense L., Panicum miliaceum L., Phalarisaquatica L. and Oryza sativa L. showed that they were comprised of numerous root primordia. Polysaccharides secreted by these suspension cultures contained glycosyl linkages consistent with the presence of high proportions of root mucilage-like polysaccharides. In contrast, suspension-cultured cells of Hordeum vulgare L. contained mostly undifferentiated cells more typical of plant cells in suspension culture. The polysaccharides secreted by H. vulgare cultures contained mostly linkages consistent with the presence of glucuronoarabinoxylan. The soluble polymers secreted by cell-suspension cultures of Phleum pratense contained 70% carbohydrate, 14% protein and 6% inorganic material. The extracellular polysaccharides were separated into four fractions by anion-exchange chromatography using a gradient of imidazole-HCl at pH 7.0. From glycosyl-linkage analyses, five polysaccharides were identified: an arabinosylated xyloglucan (comprising 20% of the total polysaccharide), a glucomannan (6%), a type-II arabinogalactan (an arabinogalactan-protein; 7%), an acidic xylan (3%), and a root-slime-like polysaccharide, which contained features of type-II arabinogalactans and glucuronomannans (65%).

Extracellular cross-linking of xylan and xyloglucan in maize cell-suspension cultures: the role of oxidative phenolic coupling

“…Such complexes are likely to be present in the protoplast (Crosthwaite et al 1994) and possibly also in the medium (Reid et al 1999;Sims et al 2000). Furthermore, proteinase treatments have been reported to degrade high-M r MLG-protein complexes in barley endosperm (Forrest and Wainwright 1977) and to aid slightly the solubilisation of xylan from rye bran (Nilsson et al 1999).…”

“…However, the detection of M r increases occurring in the PCW is difficult because M r can be measured only in soluble polysaccharides-and the alkali required for solubilisation of hemicelluloses would cleave the diferuloyl ester bonds that are suspected to act as cross-links. As a way of circumventing this problem, soluble extracellular polysaccharides (SEPs) have been proposed as informative model substrates for studying PCW polymer cross-linking because SEPs include polymers similar to those in the PCW and because their prior secretion into the medium obviates the need for solubilisation with alkali (Stevenson et al 1986;Sims et al 2000). We have shown that the SEPs of maize cell cultures increase markedly in M r several days after secretion, indicating a cross-linking process (Kerr and Fry 2003).…”

Root Exudation and Rhizosphere Biology

“…Various functions have been attributed to root cap exudation including the maintenance of root-soil contact, lubrication of the root tip, protection of roots from desiccation, stabilization of soil micro-aggregates, and selective adsorption and storage of ions (Griffin et al, 1976;Rougier, 1981;Bengough and McKenzie, 1997;Hawes et al, 2000). Root mucilage is a reasonably studied root exudate that is believed to alter the surrounding soil as it is secreted from continuously growing root cap cells (Vermeer and McCully, 1982;Ray et al, 1988;McCully, 1995;Sims et al, 2000). Soil at field capacity typically possesses a matric potential of Ϫ5 to Ϫ10 kPa (Chaboud and Rougier, 1984).…”

Extraction of extracellular polymeric substances (EPS) from anaerobic granular sludges: comparison of chemical and physical extraction protocols

“…Their composition depends on the nature of the aggregates. In pure microbial cultures or biofilms, polysaccharides are predominant (Zhang et al 1998;Sims et al 2000). In contrast, studies of EPS extracted from activated sludges show a majority of proteins (McSwain et al 2005;Ge et al 2007;Park and Novak 2007).…”