STRUCTURE OF THE PRIMARY CELL WALL OF HIGHER PLANTS, AND CONTROL OF WALL DEGRADATION BY PATHOGEN SECRETED ENZYMES. Page: 1 of 4
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THE STRUCTURE OF THE PRIMARYCELL-WALL-OF-H-IGHER_PLANTS ,AND CONTROL OF
WALL DEGRADATION BY PATHOGEN SECRETED ENZYMES.
P. Albersheim, A.J. Anderson, W.D. Bauer, K.G Keegstra and K.W. Talmadge.
Dept. of Chemistry, Univ. of Colorado, Boulder, Colo. 80302 USA
Cell walls isolated from suspension-cultured sycamore (Acer pseudoplata-
nus) cells consist of 26% cellulose, .2/% xyloglucan, 19% arabinogalactan, 15%
pectic polysaccharides and 19% hydroxyproline-rich glycoprotein with its
associated arabinosyl tetrasaccharides. These five interconnected polymers
account for essentially the entire cell wall.
The following description of cell wall structure is based on the evi-
dence available at this time. Some of the details of this model may be
altered as the results of future experiments are obtained. The elementary
cellulose fibrils are encapsulated by xyloglucan chains. The xyloglucan
chains apparently are hydrogen-bonded. along their length to the outer sur-
face of the cellulose fibrils. And, the xyloglucan chains are covalently
attached, through their reducing ends, to the arabinogalactan side chains
of the pectic polysaccharides. The pectic polysaccharides are rhamnoga-
lacturonan chains in which there are regions of uninterrupted a-1,4-linked
galacturonosyl residues, and regions in which-rhamnosyl residues are con-
centrated. In the latter regions, galacturonic acid is linked at carbon 2
of rhamnose, and rhamnose is linked at carbon 4 of galacturonic acid. Ara-
binogalactan chains form a bridge between the xyloglucan-cellulose complex
and the pectic chains. The arabinogalactan polymers are glycosidically
bonded to the pectic chains through carbon-4 of the rhamnosyl residues. The
pectic chains appear to be covalently attached through their reducing ends
to the hydroxyproline-rich protein. Our best evidence suggests that the
pectic chains are joined to the protein through a 1,3-linked galactan bridge.
This galactan, with its arabinose side chains, is probably glycosidically
bonded to the hydroxyl groups of seryl residues of the hydroxyproline-rich
protein. The hydroxyproline residues have glycosidically attached arabinose
tetrasaccharides. We have no evidence that other sugars are connected to
these arabinosyl residues.
Details of the structure of the individual polymers will be presented,
as will evidence that this proposed structure for sycamore cell walls may
be considered as a general structural model for the primary cell walls of a
variety of higher plants. -
Our studies of plant cell wall structure have been facilitated by the
use of purified degradative enzymes. The well-defined fractions thus libe-
rated were analyzed by a variety of techniques including combined gas chro-
matographic-mass spectrometric analysis of the methylated alditol acetates
derived from the polymeric constituents. These volatile derivatives of the
polysaccharides or of -the oligosaccharide fragments are synthesized by per-
methylation using the method of Hakomori; the permethylated polymers are hy-
drolyzed in trifluoroacetic acid, reduced with sodium borohydride, and the
resulting partially methylated alditols acetylated with acetic anhydride.
Computer assisted data reduction has been used to analyze the outputs of
the gas chromatographs and of the mass spectrometer.
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Albersheim, P; Anderson, A J; Bauer, W D; Keegstra, K G & Talmadge, K W. STRUCTURE OF THE PRIMARY CELL WALL OF HIGHER PLANTS, AND CONTROL OF WALL DEGRADATION BY PATHOGEN SECRETED ENZYMES., report, October 31, 1972; United States. (digital.library.unt.edu/ark:/67531/metadc1035733/m1/1/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.