dictyNews Electronic Edition Volume 36, number 18 July 1, 2011 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 ========= Microcysts: The Third Developmental Pathway of Social Amoebozoans Aldona A. Budniaka1, and Danton H. O'Day1,2 1 Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada 2 Department of Biology, University of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada The authors contributed equally to the work Protist, in press Microcyst formation and germination, the least well studied of the three alternative developmental pathways open to the social amoebozoans, is also the simplest since it involves single cells. While classical studies profiled the morphological and biochemical changes that characterize microcyst differentiation, recent studies have focused on the molecular and evolutionary aspects of this system. Microcyst differentiation (encystment) is primarily triggered by high osmolarity and to a lesser extent by starvation. The transformation of an amoeba into a microcyst involves the formation of a cellulose cell wall as well as specific enzymatic and biochemical changes leading to dormancy. The spherical microcyst remains dormant as long as high osmotic conditions persist. When the osmolarity decreases, germination begins during which the cell wall is digested as the microcyst swells followed by the emergence of an amoeba. This rapid event typically takes 3-6 hours. The relationship between encystment and sporulation, which has evolutionary significance, is also reviewed with particular emphasis on the role and regulation of actin tyrosine phosphorylation. In light of the recent sequencing of the genomes of microcyst-forming cellular slime mold species, which will generate more research on microcysts, this critical review covers past and recent research to set the stage for future work on this alternative developmental pathway. Submitted by Danton H. O'Day [danton.oday@utoronto.ca] -------------------------------------------------------------------------- Myosin-1C associates with microtubules and stabilizes the mitotic spindle during cell division Agrani Rump*+, Tim Scholz#+, Claudia Thiel*, Falk K. Hartmann*, Petra Uta#, Maike H. Hinrichs#, Manuel H. Taft* and Georgios Tsiavaliaris* *Laboratory for Cellular Biophysics, Institute for Biophysical Chemistry, Hannover Medical School, 30625 Hannover, Germany #Institute for Molecular and Cell Physiology, Hannover Medical School, 30625 Hannover, Germany + equal contribution Journal of Cell Science, in press The mitotic spindle in eukaryotic cells is composed of a bipolar array of microtubules (MTs) and associated proteins that are required during mitosis for the correct partitioning of the two sets of chromosomes to the daughter cells. In addition to the well-established functions of MT-associated proteins (MAPs) and MT-based motors in cell division, there is increasing evidence that the F-actin-based myosin motors are important mediators of F-actin-MT interactions during mitosis. Here, we report the functional characterization of the long-tailed class-1 myosin myosin-1C from Dictyostelium discoideum during mitosis. Our data reveal that myosin-1C binds to MTs and has a role in maintenance of spindle stability for accurate chromosome separation. Both myosin-1C motor function and tail domain-mediated MT-F-actin interactions are required for the cell-cycle-dependent relocalization of the protein from the cell periphery to the spindle. We show that the association of myosin-1C with MTs is mediated through the tail domain. The myosin-1C tail can inhibit kinesin motor activity, increase the stability of MTs, and form crosslinks between MTs and F-actin. These data illustrate that myosin-1C is involved in the regulation of MT function during mitosis in D. discoideum. Submitted by Georgios Tsiavaliaris [Tsiavaliaris.Georgios@mh-hannover.de] -------------------------------------------------------------------------------- For lovers of French: a new review in French about Dicty Dictyostelium discoideum : un modèle pour l'étude de la virulence bactérienne [Dictyostelium discoideum: a model for the study of bacterial virulence] Stéphanie Dallaire-Dufresne1,2, Valérie E. Paquet1,2 et Steve J. Charette1,2,3 1. Institut de biologie intégrative et des systèmes, Pavillon Charles-Eugène-Marchand, Université Laval, 1030 avenue de la Médecine, Québec, Québec, Canada, G1V 0A6 2. Centre de recherche de l'Institut universitaire de cardiologie et de pneumologie de Québec (Hôpital Laval), 2725 Chemin Sainte-Foy, Québec, Québec, Canada, G1V 4G5 3. Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, 1045 avenue de la Médecine, Québec, Québec, Canada G1V 0A6 Canadian Journal of Microbiology, in press L'amibe Dictyostelium discoideum, un prédateur bactérien, est devenue un outil précieux pour étudier la virulence bactérienne. Cet eucaryote unicellulaire possède toutes les caractéristiques qui font de lui un modèle polyvalent. Il permet d'étudier autant les facteurs de virulence des bactéries pathogènes que les éléments de l'hôte impliqués dans la résistance à l'ennemi. La virulence d'une vingtaine d'espèces de bactéries pathogènes pour l'humain ou les animaux a été étudiée avec D. discoideum jusqu'à maintenant. Ces bactéries sont autant des pathogènes extracellulaires qu'intracellulaires. La présente synthèse fait le tour de la question en portant une attention particulière sur les raisons qui font en sorte que D. discoideum est un hôte modèle adéquat pour l'étude de la virulence bactérienne et sur le type de renseignements que cette amibe permet d'obtenir sur la relation hôte-pathogène. Submitted by Steve Charette [Steve.Charette@bcm.ulaval.ca] ============================================================== [End dictyNews, volume 36, number 18]