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dictyNews Volume 34 Number 05
dictyNews
Electronic Edition
Volume 34, number 5
February 12, 2010
Please submit abstracts of your papers as soon as they have been
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or by using the form at
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Abstracts
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A cytohesin homolog in Dictyostelium amoebae
Maria Christina Shina1, Rolf Müller1, Rosemarie Blau-Wasser1, Gernot Glöckner1,2,
Michael Schleicher3, Ludwig Eichinger1, Angelika A. Noegel1, Waldemar Kolanus4
1 Center for Biochemistry, Medical Faculty, Center for Molecular Medicine Cologne
(CMMC) and Cologne Excellence Cluster on Cellular Stress Responses in
Aging-Associated Diseases (CECAD), University of Cologne, Köln, Germany,
2 Leibniz Institute for Age Research -Fritz-Lipmann-Institute e.V., Jena, Germany,
3 Institute of Anatomy and Cell Biology and Center for Integrated Protein Science
(CIPSM), Ludwig-Maximilians-University, Muenchen, Germany,
4 Laboratory of Molecular Immunology, LIMES Institute of the University of Bonn,
Bonn, Germany
PLoS ONE
Background
Dictyostelium, an amoeboid motile cell, harbors several paralogous Sec7 genes
that encode members of three distinct subfamilies of the Sec7 superfamily of
Guanine nucleotide exchange factors. Among them are proteins of the GBF/BIG
family present in all eukaryotes. The third subfamily represented with three
members in D. discoideum is the cytohesin family that has been thought to be
metazoan specific. Cytohesins are characterized by a Sec7 PH tandem domain
and have roles in cell adhesion and migration.
Principle findings
Dictyostelium SecG exhibits highest homologies to the cytohesins. It harbors at
its amino terminus several ankyrin repeats that are followed by the Sec7 PH
tandem domain. Mutants lacking SecG show reduced cell-substratum adhesion
whereas cell-cell adhesion which is important for development is not affected.
Accordingly, multicellular development proceeds normally in the mutant. During
chemotaxis secG-minus cells elongate and migrate in a directed fashion
towards cAMP, however speed is moderately reduced.
Significance
The data indicate that SecG is a relevant factor for cell-substrate adhesion
and reveal the basic function of a cytohesin in a lower eukaryote.
Submitted by Angelika Nögel [noegel@uni-koeln.de]
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The prespore cell inducing factor, psi factor (PsiA), controls both prestalk
and prespore gene expression in Dictyostelium development
Yoko Yamada1†, Hiroshi Minamisawa2, Masashi Fukuzawa3,
Takefumi Kawata2, Akiko A. Oohata1*
Dev.Growth Differ., in press
PsiA (psi factor), encoded by the psiA gene of Dictyostelium, is a secreted
signal glycoprotein that induces prespore cell differentiation when added to
monolayer cultures. In situ hybridization during normal development showed
that the psiA gene is highly expressed in scattered cells at the mound stage
and in prespore cells at the onset of culmination. The conventional
prespore-cell marker genes, cotC and pspA, were expressed normally in
psiA- and psiA overexpressing strains. Expressions of rnrB and cudA are
repressed in the prestalk cells of a wild type slug to render prespore specific
pattern. However, a promoter-reporter fusion gene, rnrB:gal, showed an
ectopic expression in the prestalk cells of psiA- strain while cudA:gal did
so in those of psiA overexpressing strain. Overexpression of psiA delayed
expression of the prestalk specific gene, ecmB, during development, while
knocking out psiA promoted its expression. In addition, overexpression
inhibited DIF-induced stalk formation in monolayer cultures. Together with
the known prespore inducing activity, the results indicate that PsiA regulates
both prespore and prestalk/stalk cell differentiation. These results indicate
that PsiA is also involved in prestalk cell differentiation.
Submitted by Akiko Oohata [oohata@makino.kmu.ac.jp]
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[End dictyNews, volume 34, number 5]
