Widespread occurrence of a covalent linkage between xyloglucan and acidic polysaccharides in suspension-cultured angiosperm cells.
OBJECTIVE
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. *


METHODS
Xyloglucan was alkali-extracted from the walls of l-[1-3H]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. Eluted fractions were Driselase-digested, yielding [3H]isoprimeverose (diagnostic of [3H]xyloglucan). The Arabidopsis cells were also fed [6-14C]glucuronic acid, and radiolabelled pectins were extracted with ammonium oxalate. *


RESULTS
[3H]Xyloglucan was detected in acidic (galacturonate-containing) as well as non-anionic polysaccharide fractions. The proportion of the [3H]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-(14)C]glucuronate, 20 % of the (galacturonate-14C)-labelled pectins were found to hydrogen-bond to cellulose, a characteristic normally restricted to hemicelluloses such as xyloglucan. *


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.
Popper
Zoë A
ZA
The Edinburgh Cell Wall Group, Institute of Molecular Plant Sciences, School of Biological Sciences, The University of Edinburgh, Daniel Rutherford Building, The King's Buildings, Mayfield Road, Edinburgh EH9 3JH, UK.
Fry
Stephen C
SC
D002473:Cell Wall / Q000737:chemistry; D002478:Cells, Cultured; D005936:Glucans / Q000737:chemistry*; D019684:Magnoliopsida / Q000737:chemistry* / Q000648:ultrastructure; D010368:Pectins / Q000737:chemistry*; D014990:Xylans / Q000737:chemistry*
D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D010368:Pectins