dictyNews Electronic Edition Volume 32, number 16 June 26, 2009 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. ========= Abstracts ========= Quantification of social behaviour in D. discoideum reveals complex fixed  and facultative strategies  Neil J. Buttery, Daniel E. Rozen, Jason B. Wolf* & Christopher R. L. Thompson* Faculty of Life Sciences, University of Manchester, Michael Smith Building,  Oxford Rd, Manchester M13 9PT, UK. *Corresponding authors Current Biology, in press The maintenance of cooperation is an evolutionary conundrum because costly  cooperative acts can be exploited by cheaters. Therefore, understanding  cooperation requires an understanding of the nature of cheaters and the  strategies used to mitigate their effects.  However, it is often difficult to  determine what accounts for differential social success, thus hindering  empirical investigation of cheating.  For example, both fixed and facultative  strategies can contribute to differential success in social interactions.   Furthermore, there is also confusion about how to distinguish social cheating  from other possible causes of unequal success in social situations that can  result in winners and losers without the need for cheating.  To study these  problems, we examined the success of naturally occurring genotypes of  Dictyostelium discoideum in social interactions.  Upon starvation, different  D. discoideum genotypes will form chimeric fruiting bodies, consisting of dead  stalk cells and viable spores.  Here, we demonstrate that an apparent  competitive dominance hierarchy of spore formation in chimera is partly due  to a fixed strategy in which genotypes exhibit dramatic differences in their  inherent allocation to stalk and spores.  However, we also demonstrate the  existence of complex facultative social interactions, where genotypes change  their spore/stalk allocation when developed in chimera, with the magnitude  and direction of changes in allocation dependent upon the genotype of their  partner.  Using these changes in allocation patterns in chimera, we further  define and partition facultative cheating into two forms: 1) promotion of individual  fitness through selfish behaviour (‘self-promotion’) and 2) coercion of other  individuals (or genotypes) to act cooperatively.  Our results demonstrate and  define social interactions between D. discoideum isolates, thus providing a  conceptual framework for the study of the genetic mechanisms that underpin  social evolution. Submitted by: Chris Thompson [christopher.thompson@manchester.ac.uk] -------------------------------------------------------------------------------- Forming Patterns in Development Without Morphogen Gradients: Scattered  Differentiation and Sorting Out Robert R. Kay1 and Christopher R.L. Thompson2 1MRC Laboratory of Molecular Biology, Hills Road, Cambridge, CB2 2QH 2Faculty of Life Sciences, University of Manchester, Michael Smith Building,  Oxford Road, Manchester M13 9PT Correspondence: christopher.thompson@manchester.ac.uk Generation and Interpretation of Morphogenetic Gradients in CSH Perspectives  in Biology Edited by James Briscoe, Peter Lawrence and Jean-Paul Vincent Few mechanisms provide alternatives to morphogen gradients for producing spatial  patterns of cells in development. One possibility is based on the sorting out of cells  that initially differentiate in a salt and pepper mixture and then physicallymove to  create coherent tissues. Here we describe the evidence suggesting this is the major  mode of patterning in Dictyostelium. In addition, we discuss whether convergent  evolution could have produced a conceptually similar mechanism in other organisms. Submitted by: Chris Thompson [christopher.thompson@manchester.ac.uk] -------------------------------------------------------------------------------- Dictyostelium Sun1 is a dynamic membrane protein of both nuclear membranes  and required for centrosomal association with clustered centromeres Irene Schulz, Otto Baumann, Matthias Samereier, Christine Zoglmeier, Ralph Gräf* University of Potsdam, Dept. of Cell Biology, 14476 Potsdam-Golm, Germany Journal: it is Eur. J. Cell Biol., in press Centrosomal attachment to nuclei is crucial for proper mitosis and nuclear  positioning in various organisms, and generally involves SUN-family proteins  located at the inner nuclear envelope. There is still no common scheme for  the outer nuclear membrane proteins interacting with SUN1 in  centrosome/nucleus attachment. Here we propose a model in which Sun1  mediates a physical link between centrosomes and clustered centromeres  through both nuclear membranes in Dictyostelium. For the first time we provide  a detailed microscopic analysis of the centrosomal and nuclear envelope  localization of endogenous Dictyostelium Sun1 during interphase and mitosis.  By immunogold electron microscopy we show that Sun1 is a resident of both  nuclear membranes. Disruption of Sun1 function by overexpression of full length  GFP-Sun1 or a GFP-SUN-domain deletion construct revealed not only the  established function in centrosome/nucleus attachment and maintenance of  ploidy, but also a requirement of Sun1 for the association of the centromere  cluster with the centrosome. Live cell imaging visualized the occurrence of mitotic  defects, and demonstrated the requirement of microtubules for dynamic distance  changes between centrosomes and nuclei. FRAP analysis revealed at least two  populations of Sun1, with an immobile fraction associated with the centrosome,  and a mobile fraction in the nuclear envelope. Submitted by: Ralph Gräf [rgraef@RZ.UNI-POTSDAM.DE] ============================================================== [End dictyNews, volume 32, number 16]