Occurrence of xyloglucan containing protuberances in the storage cell walls of cotyledons of Hymenaea courbaril L.

Abstract

-(Occurrence of xyloglucan containing protuberances in the storage cell walls of cotyledons of Hymenaea courbaril L.). Despite the suggestions of its pectic composition, no clear evidence for this has been presented. Here we show the occurrence of such a structure in walls of cells from cotyledons of Hymenaea courbariI L. These cells are known to accumulate large amounts of storage xyloglucan in the wall and, in this case, the protuberances seem to contain this storage polysaccharide rather than pectin. A hypothetical sequence of events leading from wall strands to protuberances was assembled based on scanning electron microscopy observations. On this basis, a tentative model for how polysaccharides are distributed into the wall, near the regions where protuberances are found, is proposed to explain the presence of storage xyloglucan in their composition.RESUMO -(Ocorrência de protuberâncias contendo xiloglucano nas paredes celulares da reserva de Hymenaea courbaril L.). Apesar das sugestões da sua composição péctica, não foram apresentadas evidências diretas da sua composição. Neste trabalho é mostrada a ocorrência desta estrutura em paredes de células parenquimáticas de cotilédones de Hymenaea courbaril L. Sabe-se que estas células acumulam grandes quantidades de xiloglucano nas suas paredes e, nesse caso, as protuberâncias parecem conter este polissacarídeo na sua constituição. Uma seqüência de eventos que leva ao aparecimento destas protuberâncias é sugerida e um modelo de parede celular é proposto para explicar a presença de xiloglucano de reserva na composição das protuberâncias.

Seed Cell Wall Storage Polysaccharides: Models to Understand Cell Wall Biosynthesis and Degradation

“…Pectin polymers are also found as CWSPs, notably arabinogalactan (Crawshaw and Reid, 1984;Parker, 1984;Buckeridge et al, 2000b). In cotyledons of lupin (Lupinus angustifolius), the chemical structure is a b-(1,4)-linked D-galactan with branches of a-(1,5)-Ara (Hirst et al, 1947).…”

“…The location of storage xyloglucans may possibly explain the lack of action of the exohydrolases on the polymers but only on oligosaccharides (see below). Tiné et al (2000b) found that the storage cell walls of H. courbaril forms protuberances that make bridges between cotyledon cells that store xyloglucan. These bridges seem to hold cells together along with a middle lamella, but at the same time with intercellular spaces that are thought to be filled with water during imbibition.…”

“…Several species from various families are known to have seeds that store mannan, glucomannan, or galactomannan (Meier and Reid, 1982;Buckeridge et al, 2000b).…”

“…fenugreek) to an average of ratio of 3:1 or 4:1 (carob [Ceratonia siliqua]). A typical distribution of M:G ratios in legumes gives a bimodal shaped curve (Buckeridge et al, 1995(Buckeridge et al, , 2000b, associated with the subfamily to which the species belong. Members of the subfamily Caesalpinioideae have poorly substituted galactomannans and it has been demonstrated that the polysaccharide is edited during deposition in the wall, presumably by a debranching a-galactosidase (Edwards et al, 1992).…”

Intercellular Pectic Protuberances in Asplenium: New Data on their Composition and Origin

“…RGII has a backbone of HG rather than RG, with complex side chains attached to the GalA residues (Willats et al, 2006). Using chemical stains, other constituents of the primary cell wall were also detected in IPPs: cellulose in Picea (Miller and Barnett, 1993), xyloglucan in Hymenaea (Tiné et al, 2000), proteins and callose in Azolla (Veys et al, 1999).…”