Transport, degradation and cell wall-integration of XXFGol, a growth-regulating nonasaccharide of xyloglucan, in pea stems

Abstract

When [glucitol-3 H]XXFGol (a NaB 3 H 4 -reduced xyloglucan nonasaccharide) was applied to excised shoots of pea (Pisum sativum L. cv. Progress) at the base of the epicotyl, it inhibited growth in the elongation zone, 4±5 cm distal. Experiments were conducted to discover whether such 3 H-oligosaccharides are translocated intact over this distance, or whether an intercellular second messenger would have to be postulated. After 24 h, 3 H from [glucitol-3 H]XXFGol and [glucitol-3 H]XXXGol showed U-shaped distributions, with most 3 H at the base and apex of the stem. Radioactivity from [fucosyl-3 H]XXFG and [xylosyl-3 H]XXFG also moved acropetally, but did not concentrate at the apex, possibly owing to removal from the transpiration stream of fucose and xylose formed by partial hydrolysis of XXFG en route. When 10 A7 M [glucitol-3 H]XXFGol was supplied, about 14 fmol á seedling ±1 of apparently intact [ 3 H]XXFGol was extractable from the elongation zone after 24 h. Larger amounts of degradation products were extractable (including free [ 3 H]glucitol) and some wall-bound 3 H-hemicellulose was present (presumably formed by the oligosaccharides acting as acceptor substrates for transglycosylation). We conclude that biologically active oligosaccharides of xyloglucan can move through the stem acropetally and that they are maintained at low steady-state concentrations by both hydrolysis and transglycosylation.

Biosynthetic origin and longevity in vivo of α- d -mannopyranosyl-(1 → 4)-α- d -glucuronopyranosyl-(1 → 2)- myo -inositol, an unusual extracellular oligosaccharide produced by cultured rose cells

“…They have been proposed to play important intercellular signalling roles in higher plants (York et al 1984;Darvill et al 1992; Fry 1993, 1994;Auxtova et al 1995;Warneck et al 1998). In studies of their physiological roles, it would be of great interest to investigate changes in the extraprotoplasmic concentrations of endogenous oligosaccharins, e.g.…”

Release, Recycle, Rebuild: Cell-Wall Remodeling, Autodegradation, and Sugar Salvage for New Wall Biosynthesis during Plant Development

“…Incubating plants with fluorescent sulforhodamine-conjugated XyG oligosaccharide (XGO) probes demonstrates that exogenous XyG fragments are incorporated into tissues with high XET activity, such the elongation zones of Arabidopsis and tobacco roots (Vissenberg et al, 2000). Apoplastic XyG incorporation has also been observed in rapidly expanding regions of excised pea stems (Warneck et al, 1998). Application of intact XyG to pea stems reduces wall extension and increases wall stiffness, likely due to tethering of large XyG fragments via XET activity, but incubation with small XGOs encourages growth and wall flexibility at higher concentrations (Takeda et al, 2002).…”

“…Low concentrations of calcium also stimulated arabinose incorporation into maize coleoptile cell walls (Carpita et al, 1982), which might be connected to the degradation of calcium-complexed HG. Furthermore, some evidence supports the possibility of longrange transport of matrix polysaccharides through the vasculature in excised stems; these polysaccharides could be used to support new growth in elongating tissues (Baydoun and Fry, 1985;Warneck et al, 1998), but this type of transport has not been shown to occur in intact plants. Synthesis of these data indicates that cell elongation and sugar salvage resulting from cell-wall degradation are tightly correlated processes, but whether one drives the other remains to be determined.…”

Plant oligosaccharides — outsiders among elicitors?

“…Oligosaccharin is trans ported in plants through the xylem. This conclusion is based on the distribution of label after incorporation into a plant of labeled oligogalacturonides [87], xyloglucan fragments [88], as well as N glycan oligosaccharide frag ments into a plant [89]. Experiments on the influence of oligosaccharides on low temperature adaptation serves as another argument for the existence of upward transport of oligosaccharides [37,60]: oligosaccharin added to the growth medium of winter wheat seedlings (Triticum aes tivum L.) stimulated increase of resistance measured by the yield of electrolytes from leaves, which could be indi rect evidence of its upward movement in the plant; how ever, labeled oligosaccharin were not studied in these works.…”

“…For instance, oligogalact uronides can be cleaved into smaller oligomers or bind an unidentified alcohol [87]. Xyloglucan fragments are also modified and undergo degradation during transport, but some xyloglucan fragments (XXFG), added exogenously, and transported in pea seedlings over a distance of 5 6 cm, remained unaltered even 24 h after introduction into the stem [88].…”