Glycosyl composition and linkage analysis of cell wall
polysaccharides were examined in apical root zones excised from water-stressed and unstressed wheat seedlings (Triticum durum Desf.) cv. Capeiti ("drought-tolerant") and cv. Creso ("drought sensitive"). Wall
polysaccharides were sequentially solubilized to obtain three fractions: CDTA+Na(2)CO(3) extract, KOH extract and the insoluble residue (
alpha-cellulose). A comparison between the two genotypes showed only small variations in the percentages of matrix
polysaccharides (CDTA+Na(2)CO(3) plus KOH extract) and of the insoluble residues (
alpha-cellulose) in water-stressed and unstressed conditions. Xylosyl, glucosyl and arabinosyl residues represented more than 90 mol% of the matrix
polysaccharides. The linkage analysis of matrix
polysaccharides showed high levels of xyloglucans (23-39 mol%), and arabinoxylans (38-48 mol%) and a low amount of
pectins and (1-->3), (1-->4)-beta-D-
glucans. The high level of xyloglucans was supported by the release of the diagnostic
disaccharide isoprimeverose after
Driselase digestion of KOH-extracted
polysaccharides. In the "drought-tolerant" cv. Capeiti the mol% of side chains of
rhamnogalacturonan I and II significantly increased in response to
water stress, whereas in cv. Creso, this increase did not occur. The results support a role of the pectic side chains during
water stress response in a drought-tolerant wheat cultivar.