dictyNews Electronic Edition Volume 34, number 5 February 12, 2010 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. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= 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] -------------------------------------------------------------------------------- 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] ============================================================== [End dictyNews, volume 34, number 5]