dictyNews Electronic Edition Volume 34, number 3 January 22, 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 coronin7 homolog with functions in actin-driven processes Maria C. Shina, Can Ünal, Ludwig Eichinger, Annette Müller-Taubenberger, Michael Schleicher, Michael Steinert, Angelika A. Noegel J. Biol. Chem., in press Dictyostelium discoideum Coronin7 (DdCRN7) together with human Coronin7 (CRN7) and Pod-1 of Drosophila melanogaster and Caenorhabditis elegans belong to the coronin family of WD repeat domain containing proteins. Coronin7 proteins are characterized by two WD repeat domains that presumably fold into two beta-propeller structures. DdCRN7 shares highest homology with human CRN7, a protein with roles in membrane trafficking. DdCRN7 is present in the cytosol and accumulates in cell surface projections during movement and phago- and pinocytosis. Cells lacking CRN7 have altered chemotaxis and phagocytosis. Furthermore, loss of CRN7 affects the infection process by the pathogen Legionella pneumophila and allows a more efficient internalization of bacteria. To provide a mechanism for CNR7 action we studied actin related aspects. We could show that CRN7 binds directly to F-actin and protects actin filaments from depolymerization. CRN7 also associated with F-actin in vivo. It was present in the Triton X-100 insoluble cytoskeleton, colocalized with F-actin and its distribution was sensitive to drugs affecting the actin cytoskeleton. We propose that CRN7's role in chemotaxis and phagocytosis is through its effect on the actin cytoskeleton. Submitted by Angelika Noegel [noegel@uni-koeln.de] -------------------------------------------------------------------------------- Cheating by Exploitation of Developmental Prestalk Patterning in Dictyostelium discoideum Anupama Khare and Gad Shaulsky; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, USA PLoS Genetics, in press The cooperative developmental system of the social amoeba Dictyostelium discoideum is susceptible to exploitation by cheaters – strains that make more than their fair share of spores in chimerae. Laboratory screens in Dictyostelium have shown that the genetic potential for facultative cheating is high and field surveys have shown that cheaters are abundant in nature, but the cheating mechanisms are largely unknown. Here we describe cheater C (chtC), a strong facultative cheater mutant that cheats by affecting prestalk differentiation. The chtC gene is developmentally regulated and its mRNA becomes stalk-enriched at the end of development.  chtC mutants are defective in maintaining the prestalk cell fate as some of their prestalk cells transdifferentiate into prespore cells, but that defect does not affect gross developmental morphology or sporulation efficiency.   In chimerae between wild-type and chtC mutant cells, the wild-type cells preferentially give rise to prestalk cells, and the chtC mutants increase their representation in the spore mass. Mixing chtC mutants with other cell-type proportioning mutants revealed that the cheating is directly related to the prestalk-differentiation propensity of the victim. These findings illustrate that a cheater can victimize cooperative strains by exploiting an established developmental pathway. Submitted by Gad Shaulsky [gadi@bcm.edu] ============================================================== [End dictyNews, volume 34, number 3]