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Science 23 October 1998:
Vol. 282. no. 5389, p. 591
DOI: 10.1126/science.282.5389.591a
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Technical Comments
Cellulose Biosynthesis in Arabidopsis
The observations reported by Tony Arioli et al.
(1) represent an important contribution to
characterizing the complex processes of biogenesis of cellulose in
higher plants. The results presented and further discussed by Carpita
and Vergara (2) do not exclude alternative interpretations
consistent with the observations. The alternatives are suggested by the
occurrence of significant amounts of a soluble  -1,4-linked glucan
in the instances wherein the action of the cellulose synthase was
perturbed by growth at 31°C. The cello-oligosaccharides are known to
become insoluble at the octamer (3). Furthermore,
substitution at a single hydroxyl of one in ten anhydroglucose units
can make cellulose soluble in neutral aqueous media. Observations of a soluble -1,4-linked glucan led Colvin to propose, in 1974, that Acetobacter xylinum can produce a "soluble cellulose"
(4). Permethylation analyses later showed low
levels of -1,2-linked glucose units along the chain. Arioli
et al. may be observing a similar gluco-glucan of limited
substitution. The occurrence of such a glucan would not be detected in
the hydrolysis-based analyses usually applied to cell wall
polysaccharides, and the permethylation analysis described by
Arioli et al. is focused on excluding the -1,3-linked
callose, which is frequently observed when cellulose synthase activity
is disrupted.
Two alternative interpretations of the soluble -1,4-linked glucan
suggest themselves. First, the mutant could have a synthase of limited
stability, that can have its specificity for -1,4 glycosylation
perturbed enough at 31°C to result in occasional nonspecific
linkages, resulting in a gluco-glucan with substitution sufficient to
make it soluble. Second, the soluble glucan could be a precursor to
cellulose that is stripped of its substituents under normal conditions,
a process that could be disrupted at 31°C in the mutant
(5).
Careful permethylation analyses of the soluble -1,4-linked glucan,
with particular attention to minor components, will be important to
full development of the implications of the observations made by Arioli
et al. (1).
R. H. Atalla
Forest Products Laboratory,
Forest Service,
U.S. Department of
Agriculture,
Madison, WI 53705, USA
E-mail:
rhatalla{at}facstaff.wisc.edu
REFERENCES
-
T. Arioli,
et al.,
Science
279,
717
(1998)
[Abstract/Free Full Text]
.
-
N. Carpita and C. Vergara, ibid., p. 672.
-
B. A. Tonnesen and O. Ellefsen, in Cellulose and
Cellulose Derivatives, N. M. Bikales and L. Segal, Eds.
(Wiley-Interscience, New York, 1971), p. 265.
-
J. R. Colvin, lecture at the Institute of Paper Chemistry,
Appleton, WI (1974);
___,
L. Chene,
L. C. Sowden,
M. Takai,
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1057
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[ISI] [Medline]
;
L. C. Sowden and
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R. Colvin,
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[ISI] [Medline]
;
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[ISI] [Medline]
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R. H. Atalla, Holzforschung, in press.
11 May 1998; accepted 5 October 1998
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