RESUMO
An Arabidopsis thaliana mutant (mur1) has less than 2 percent of the normal amounts of L-fucose in the primary cell walls of aerial portions of the plant. The survival of mur1 plants challenged the hypothesis that fucose is a required component of biologically active oligosaccharides derived from cell wall xyloglucan. However, the replacement of L-fucose (that is, 6-deoxy-L-galactose) by L-galactose does not detectably alter the biological activity of the oligosaccharides derived from xyloglucan. Thus, essential structural and conformational features of xyloglucan and xyloglucan-derived oligosaccharides are retained when L-galactose replaces L-fucose.
Assuntos
Arabidopsis/química , Parede Celular/química , Fucose/análise , Galactose/análise , Glucanos , Polissacarídeos/química , Xilanos , Ácido 2,4-Diclorofenoxiacético/farmacologia , Arabidopsis/genética , Arabidopsis/fisiologia , Configuração de Carboidratos , Sequência de Carboidratos , Parede Celular/fisiologia , Fucose/fisiologia , Fucosiltransferases/metabolismo , Galactose/fisiologia , Espectroscopia de Ressonância Magnética , Dados de Sequência Molecular , Mutação , Oligossacarídeos/farmacologia , Pisum sativum , Caules de Planta/efeitos dos fármacos , Caules de Planta/crescimento & desenvolvimento , Espectrometria de Massas de Bombardeamento Rápido de ÁtomosRESUMO
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%), rhamnogalacturonon 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 structure of the Arabidopsis cell-wall polysaccharides are typical of those of many other plants.
