center dot Background and Aims Covalent linkages between xyloglucan and rhamnogalacturonan-I (RG-I) have been reported in the primary cell walls of cultured Rosa cells and may contribute to wall architecture. This study investigated whether this chemical feature is general to angiosperms or whether Rosa is unusual.
center dot Methods Xyloglucan was alkali-extracted from the walls of L-[1-H-3]arabinose-fed suspension-cultured cells of Arabidopsis, sycamore, rose, tomato, spinach, maize and barley. The polysaccharide was precipitated with 50 % ethanol and subjected to anion-exchange chromatography in 8 m urea. Fluted fractions were Driselase-digested, yielding [3H]isoprimeverose (diagnostic of [H-3]xyloglucan). The Arabidopsis cells were also fed [6-C-14]glucuronic acid, and radiolabelled pectins were extracted with ammonium oxalate.
center dot Key Results [3 H]Xyloglucan was detected in acidic (galacturonate-containing) as well as non-anionic polysaccharide fractions. The proportion of the [3 H]isoprimeverose units that were in anionic fractions was: Arabidopsis, 45 %; sycamore, 60 %; rose, 44 %; tomato 75 %; spinach, 70 %; maize, 50 %; barley, 70 %. In Arabidopsis cultures fed D-[6-C-14] glucuronate, 20 % of the (galacturonate-C-14)-labelled pectins were found to hydrogen-bond to cellulose, a characteristic normally restricted to hemicelluloses such as xyloglucan.
center dot Conclusions Alkali-stable, anionic complexes of xyloglucan (reported in the case of Rosa to be xyloglucan-RG-I covalent complexes) are widespread in the cell walls of angiosperms, including gramineous monocots.