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dictyNews Volume 31 Number 09
dictyNews
Electronic Edition
Volume 31, number 9
September 12, 2008
Please submit abstracts of your papers as soon as they have been
accepted for publication by sending them to dicty@northwestern.edu
or by using the form at
http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.
Upon publication of your paper, please send strains and plamids to
the Dicty Stock Center. For more information see
http://dictybase.org/StockCenter/Deposit.html.
Back issues of dictyNews, the Dicty Reference database and other
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Abstracts
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Dependence of Stress Resistance on a Spore Coat Heteropolysaccharide in
Dictyostelium
Christopher M. West (1), Phuong Nguyen (1), Hanke van der Wel (1),
Talibah Metcalf (1), Kristin R. Sweeney (2), Ira J. Blader (2), and
Gregory W. Erdos (3)
(1) Dept. of Biochemistry & Molecular Biology and Oklahoma Center for Medical
Glycobiology
(2) Dept. of Microbiology and Immunology, University of Oklahoma Health
Sciences Center, Oklahoma City, OK 73104 USA
(3) ICBR, University of Florida, Gainesville, FL 32611 USA
Eukaryotic Cell, in press
In Dictyostelium, sporulation occurs synchronously as prespore cells
approach the apex of the aerial stalk during culmination. Each prespore cell
becomes surrounded by its own coat comprised of a core of crystalline cellulose
and a branched heteropolysaccharide sandwiched between heterogeneous
cysteine-rich glycoproteins. The function of the heteropolysaccharide, which
consists of galactose and N-acetylgalactosamine, is unknown. Two
glycosyltransferase-like genes encoding multifunctional proteins each with
predicted features of a heteropolysaccharide-synthase were identified in
the D. discoideum genome. pgtB and pgtC transcripts were modestly upregulated
during early development and pgtB was further intensely upregulated at the
time of heteropolysaccharide accumulation. Disruption of either gene reduced
synthase-like activity and blocked heteropolysaccharide formation, based on
loss of cytological labeling with a lectin and absence of component sugars
after acid hydrolysis. Cell mixing experiments showed that heteropolysaccharide
expression is spore cell autonomous, suggesting a physical association with
other coat molecules during assembly. Mutant coats expressed reduced levels
of crystalline cellulose based on chemical analysis after acid degradation,
and cellulose was heterogeneously affected based on flow cytometry and
electron microscopy. Mutant coats also contained elevated levels of selected
coat proteins but not others, and were sensitive to shear. Mutant spores were
unusually susceptible to hypertonic collapse and damage by detergent or
hypertonic stress. Thus the heteropolysaccharide is essential for spore
integrity, which can be explained by a role in the formation of crystalline
cellulose and regulation of the protein content of the coat.
Submitted by: Chris West [Cwest2@ouhsc.edu]
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[End dictyNews, volume 31, number 9]
