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 pect ic polysaccharides homogalacturonan, rhamnogalacturonan I, and rhamnog alacturonan II, the two hemicelluloses xyloglucan and glucuronoarabino xylan, and structural glycoproteins. The cell walls of Arabidopsis lea ves contain each of these components and no others that we could detec t, and these cell walls are remarkable in that they are particularly r ich in phosphate buffer-soluble polysaccharides (34% of the wall). The pectic polysaccharides of the purified cell walls consist of rhamnoga lacturonan I (11%), rhamnogalacturonan II (8%), and homogalacturonan ( 23%). Xyloglucan (XG) accounts for 20% of the wall, and the oligosacch aride fragments generated from XG by endoglucanase consist of the typi cal subunits of other higher plant XGs. Glucuronoarabinoxylan (4%), ce llulose (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 si milar to those of other plants. The structures of the Arabidopsis cell -wall polysaccharides are typical of those of many other plants.