Xyloglucan structure and post‐germinative metabolism in seeds of Copaifera langsdorfii from savanna and forest populations

Abstract

The cotyledons of Copaifera langsdorfii Desf, have been shown to contain a water‐soluble xyloglucan (amyloid), which represents about 40% of the seed's dry weight. On acid hydrolysis its composition (Glc:Xyl:Gal = 4.0:2.8–2.9:1.5–1.7) was similar to that of the well‐characterized xyloglucan of Tamarindus indica L. (Glc:Xyl:Gal = 4.0:3.0–3.1:1.4). On hydrolysis with pure Trichoderma viride cellulase, both C. langsdorfii and T. indica xyloglucan gave the same xyloglucan oligosaccharides: but in significantly different proportions A:B1:B2:C = 1:0.4–0.5:2.1–2.2:3.1–3.4 in T. indica, and 1:1.1:1.8:7.4 and 1:1.3:2.6:12 for C. langsdorfii, savanna and forest populations respectively. This demonstrated a difference in fine molecular structure, notably in the distribution of the terminal non‐reducing galactose substituents, between the xyloglucans of the two species and indicated differences in the specificities of their biosynthetic mechanisms. The xyloglucans obtained from C. langsdorfii seeds harvested from savanna and forest environments were slightly different, one from the other, in their sugar‐residue composition (Glc:Xyl:Gal = 4.0:2.9:1.5 and 4.0:2.8:1.7, respectively), and were significantly different in the relative proportions of the xyloglucan oligosaccharides released on cellulase hydrolysis (above). Using light microscopy and biochemical methods, no difference in the pattern or rate of postgerminative xyloglucan metabolism was detected in seeds of savanna and forest origin. This is the first clear experimental evidence for differences in a storage xyloglucan structure between populations of the same species. It may indicate environmental influences on xyloglucan biosynthesis.

A xyloglucan oligosaccharide‐active, transglycosylating‐D‐glucosidase from the cotyledons of nasturtium (Tropaeolum majus L) seedlings – purification, properties and characterization of a cDNA clone

“…The heptasaccharide and the nonasaccharide fractions were pure XXXG and XLLG, respectively, and the octasaccharide fraction was a mixture of XXLG and XLXG in the molar proportions 1:5.7 (Buckeridge et al, 1992;Fanutti et al, 1993;York et al, 1990). The enzyme did not release glucose from these compounds, as might be expected since in each of them the non-reducing terminal glucose residue carries an α-xylosyl substituent.…”

“…The storage xyloglucans from seeds are closely similar in their structural features to the hemicellulosic xyloglucans of plant primary cell walls (Hayashi, 1989), but the seed polymers are not fucosylated. Recent studies of seed xyloglucans show that they consist almost entirely of the structural subunits XXXG, XXLG, XLXG and XLLG, although in varying proportions (Buckeridge et al, 1992;Fanutti et al, 1996;Gidley et al, 1991;York et al, 1990) according to the botanical source. Unlike the primary cell wall xyloglucans, seed xyloglucans are very easily extracted from the plant tissues with hot water (Reid, 1985).…”

“…The post-germinative mobilization of seed xyloglucans has been studied both ultrastructurally and biochemically (Buckeridge et al, 1992;Edwards et al, 1985;Reis et al, 1987). Nasturtium xyloglucan mobilization involves the simultaneous action of four enzymes, a xyloglucan-specific endo-(1→4)-β-D-glucanase or xyloglucan endo-transglycosylase (XET) (Edwards et al, 1986;Fanutti et al, 1993Fanutti et al, , 1996Farkas et al, 1992;de Silva et al, 1993), a β-galactosidase with action both on polymeric xyloglucan and its subunit oligosaccharides Reid et al, 1988), a xyloglucan oligosaccharide-specific α-xylosidase or oligoxyloglucan exo-xylohydrolase Fanutti et al, 1991), and a β-glucosidase (Edwards et al, 1985).…”

The Control of Storage Xyloglucan Mobilization in Cotyledons of Hymenaea courbaril

“…The reserve function of xyloglucan in cotyledons has been demonstrated for seeds of nasturtium (Edwards et al, 1985), Tamarindus indica (Reis et al, 1987), Copaifera langsdorffii (Buckeridge et al, 1992), and Hymenaea courbaril , where xyloglucan mobilization in vivo is followed by the rise and fall of the activities of four hydrolases: b-galactosidase, endob-(1fi4)-D-glucanase (or xyloglucan transglycosylase hydrolase [XTH], which is a term used for the gene or protein that can have endo-transglycosylase [XET] or endo-b-hydrolase [XEH; hydrolase] activity [Rose et al, 2002]), a-xylosidase, and b-glucosidase.…”

“…In C. langsdorffii, the mobilization of the cotyledon cell wall storage has been observed cytochemically, physiologically, and biochemically by Buckeridge et al (1992). They have studied two different populations from two different biomes (forest and savannah) and did not find apparent differences in xyloglucan mobilization between seeds from the two environments.…”