Pectic Polysaccharide Fraction from Zea Shoots1

A pectic fraction, accounting for about 0.3% of the total cell wall polysaccharide, was derived from the hot water extract of an insoluble fraction of the buffer-homogenate of Zea shoots. The pectic polysaccharide fraction was characterized by fragmentation analysis after hydrolysis with acid and Erwinia carotovora pectate lyase. The results suggest that the fraction consists of mostly a linear homopolygalacturonan with neutral sugar components or a homogalacturonan and a rhamnogalacturonan with neutral sugar components. To learn the nature of structural features of cell walls in elongating monocot tissues, we initiated a detailed study on Zea shoot cell-wall polysaccharides. In previous reports we reported on the structural characterization of the arabino-3,6galactan obtained from a soluble fraction of the buffer-homogenate of Zea shoots (6), and of the (1-s3),(l-)-,3-D glucan and (l-3)-f-D-glucan, which were obtained by treatment of an insoluble fraction of the buffer-homogenate of Zea shoots with 3 M LiCl and hot water (8, 9). In the course of structural studies of polysaccharides obtained by treatment of an insoluble fraction of the buffer-homogenate of Zea shoots with hot water, we prepared a pectic polysaccharide fraction. The pectic polysaccharides of the primary cell walls of monocots have not been studied extensively, although it is clear that monocot cell walls possess relatively small amounts of GalUA2 (3, 12). This report is the fourth in a series of dealing with the water-soluble polysaccharides of Zea shoots and describes the structure of a pectic polysaccharide fraction from Zea shoots. MATERIALS AND METHODS