dictyNews Electronic Edition Volume 38, number 16 June 29, 2012 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 ========= Mind the gap: a comparative study of migratory behavior in social amoebae Owen M. Gilbert, Jennie J. Kuzdzal-Fick, David C. Queller, Joan E. Strassmann Behavioral Ecology and Sociobiology, in press Social amoebae aggregate to form a multicellular slug that migrates some distance. Most species produce a stalk during migration, but some do not. We show that D. giganteum, a species that produces stalk during migration, is able to traverse small gaps and utilize bacterial resources following gap traversal by shedding live cells. In contrast, we found D. discoideum, a species that does not produce stalk during migration, can traverse gaps only when in the presence of other speciesÕ stalks, or other thin filaments. These findings suggest production of stalk during migration allows traversal of gaps, as commonly occur in soil and leaf litter. Considering the functional consequences of a stalked migration may be important for explaining the evolutionary maintenance or loss of a stalked migration. Submitted by Owen Gilbert [owen.gilbert@gmail.com] -------------------------------------------------------------------------------------- Dictyostelium uses the prokaryote messenger c-di-GMP to trigger stalk cell differentiation. Zhi-hui Chen and Pauline Schaap* College of Life Sciences, University of Dundee, Dundee DD15EH, UK Nature, in press Cyclic di-(3Õ:5Õ)-guanosine monophosphate (c-di-GMP) is a major prokaryote signalling intermediate, which is synthesized by diguanylate cyclases and triggers sessility and biofilm formation. We detected the first eukaryote diguanylate cyclases (DgcAs) in all major groups of Dictyostelia. Upon food depletion, Dictyostelium discoideum amoebas collect into aggregates, which first transform into migrating slugs and next into sessile fruiting structures. These structures consist of a spherical spore mass that is supported by a column of stalk cells and a basal disk. A polyketide, DIF-1, was isolated earlier, which induces stalk-like cells in vitro. However, its role in vivo proved recently to be restricted to basal disk formation. Here we show that Dictyostelium DgcA produces c-di-GMP as the morphogen responsible for stalk cell differentiation. D.discoideum DgcA synthesized c-di-GMP in a GTP-dependent manner and was expressed at the slug tip, the site of stalk cell differentiation. Disruption of the DgcA gene blocked the transition from slug migration to fructification and the expression of stalk genes. Fructification and stalk formation were restored by exposing dgca- slugs to wild-type secretion products or to c-di-GMP. Moreover, c-di-GMP, but not c-di-AMP, induced stalk gene expression in dilute cell monolayers. Apart from identifying the long elusive stalk-inducing morphogen, our work also identifies the first role for c-di-GMP in eukaryotes. Submitted by Pauline Schaap [p.schaap@dundee.ac.uk] -------------------------------------------------------------------------------------- Structured growth and genetic drift raise relatedness in the social amoeba Dictyostelium discoideum. Neil J. Buttery(1), Chandra N. Jack(2), Boahemaa Adu-Oppong(1), Kate T. Snyder(3), Christopher R.L. Thompson(4), David C. Queller(1) and Joan E. Strassmann(1) (1) Department of Biology, Campus Box 1137, Washington University in Saint Louis, One Brookings Drive, Saint Louis, Missouri, USA (2) Department of Bioengineering, Rice University, 6100 Main Street, Houston, Texas, USA (3) Department of Ecology and Evolution, Rice University, 6100 Main Street, Houston, Texas, USA (4) Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, UK Biology Letters, in press One condition for the evolution of altruism is genetic relatedness between altruist and beneficiary, often achieved through active kin recognition. Here we investigate the power of a passive process resulting from genetic drift during population growth in the social amoeba Dictyostelium discoideum. We put labelled and unlabelled cells of the same clone in the centre of a plate, and allowed them to proliferate outward. Zones formed by genetic drift, due to the small population of actively growing cells at the colony edge. We also found that single cells could form zones of high relatedness. Relatedness increased at a significantly higher rate when food was in short supply. This study shows that relatedness can be significantly elevated before the social stage without a small founding population size or recognition mechanism. Submitted by Neil Buttery [buttery@wustl.edu] -------------------------------------------------------------------------------------- Innate Non_Specific Cell Substratum Adhesion Loomis, W.F., Fuller, D., Gutierrez, E., Groisman, A., and Rappel, W-J. Section of Cell and Developmental Biology, Division of Biological Sciences, Department of Physics, Center for Theoretical Biological Physics University of California, San Diego , La Jolla, CA PLoS ONE, in press Adhesion of motile cells to solid surfaces is necessary to transmit forces required for propulsion. Unlike mammalian cells, Dictyostelium cells do not make integrin mediated focal adhesions. Nevertheless, they can move rapidly on both hydrophobic and hydrophilic surfaces. We have found that adhesion to such surfaces can be inhibited by addition of sugars or amino acids to the buffer. Treating whole cells with _-mannosidase to cleave surface oligosaccharides also reduces adhesion. The results indicate that adhesion of these cells is mediated by van der Waals attraction of their surface glycoproteins to the underlying substratum. Since glycoproteins are prevalent components of the surface of most cells, innate adhesion may be a common cellular property that has been overlooked. Submitted by Bill Loomis [wloomis@ucsd.edu] ============================================================== [End dictyNews, volume 38, number 16]