Auxin-induced changes in the molecular weight of hemicellulosic polysaccharides of the Avena coleoptile cell wall
Sakurai N,Nishitani K, Masuda Y
Plant Cell Physiol 20:1349-1357
The average molecular weight of the water soluble hemicellulose (hemicellulose B) of the Avena coleoptile cell wall was determined by gel permeartion chromatography (GPC) and viscometry. Analysis of the neutral sugar composition of hemicellulose B eluted from a GPC columu (Sepharose 4B) indicated that it consists of ΐ-glucan with a hegh molecular weight and arabinoxylan with a low molecular weight. A kinetic studyof the effect of auxin on the molecular distribution of hemicellulose B demonstrated that auxin decreased theΐ-glucan content of the hemicellulose as early as the first hour incubation, but not the arabinoxylan content, when it stimulated the extension of the coleoptile segment. Calculation of the weight-average molecular weight from the chromatograms suggested that auxin decreased the molecular weight of hemicelluloseB; this was also confirmed by viscometry. Thus, auxin may cause cell wall loosening, leading to cell extension, through its effect onΐ-glucan degradation or through the decrease in the molecular weight of hemicellulose B.