STRUCTURE OF PLANT-CELL WALLS .34. CHARACTERIZATION OF THE CELL-WALL POLYSACCHARIDES OF ARABIDOPSIS-THALIANA LEAVES

The cell-wall polysaccharides of Arabidopsis thaliana leaves have been isolated, purified, and characterized. The primary cell walls of all higher plants that have been studied contain cellulose, the three pectic polysaccharides homogalacturonan, rhamnogalacturonan I, and rhamnogalacturonan II, the two hemicelluloses xyloglucan and glucuronoarabinoxylan, and structural glycoproteins. The cell walls of Arabidopsis leaves contain each of these components and no others that we could detect, and these cell walls are remarkable in that they are particularly rich in phosphate buffer-soluble polysaccharides (34% of the wall). The pectic polysaccharides of the purified cell walls consist of rhamnogalacturonan I (11%), rhamnogalacturonan II (8%), and homogalacturonan (23%). Xyloglucan (XG) accounts for 20% of the wall, and the oligosaccharide fragments generated from XG by endoglucanase consist of the typical subunits of other higher plant XGs. Glucuronoarabinoxylan (4%), cellulose (14%), and protein (14%) account for the remainder of the wall. Except for the phosphate buffer-soluble pectic polysaccharides, the polysaccharides of Arabidopsis leaf cell walls occur in proportions similar to those of other plants. The structures of the Arabidopsis cell-wall polysaccharides are typical of those of many other plants.