dictyNews Electronic Edition Volume 41, number 7 April 10, 2015 Please submit abstracts of your papers as soon as they have been accepted for publication 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 ========= Fitness trade-offs result in the illusion of social success Jason B. Wolf1* Jennifer A. Howie2, Katie Parkinson2, Nicole Gruenheit2, Diogo Melo3, Daniel Rozen4, and Christopher R.L. Thompson2* 1 Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK 2 Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Rd, Manchester, M13 9PT, UK 3 Departamento de Gentica e Biologia Evolutiva, Instituto de Biocincias, Universidade de So Paulo, So Paulo, SP, Brazil 4 Institute of Biology, Leiden University, Sylvius Laboratory, Sylviusweg 72, PO Box 9505, 2300 RA Leiden, The Netherlands * Corresponding authors Current Biology, in press Cooperation is ubiquitous across the tree of life, from simple microbes to the complex social systems of animals [1]. Individuals cooperate by engaging in costly behaviours that can be exploited by other individuals who benefit by avoiding these associated costs. Thus, if successful exploitation of social partners during cooperative interactions increases relative fitness, then we expect selection to lead to the emergence of a single optimal winning strategy in which individuals maximize their gain from cooperation while minimizing their associated costs [2]. Such social cheating appears to be widespread in nature [3], including several microbial systems [4-11], but despite the fitness advantages favouring social cheating, populations tend to harbour significant variation in social success rather than a single optimal winning strategy. Using the social amoeba Dictyostelium discoideum we provide a possible explanation for the coexistence of such variation. We find that genotypes typically designated as cheaters [12] because they produce a disproportionate number of spores in chimeric fruiting bodies, do not actually gain higher fitness as a result of this apparent advantage because they produce smaller, less viable, spores than putative losers. As a consequence of this trade-off between spore number and viability, genotypes with different spore production strategies, which give the appearance of differential social success, ultimately have similar realised fitness. These findings highlight the limitations of using single fitness proxies in evolutionary studies and suggest that interpreting social trait variation in terms of strategies like cheating or cooperating may be misleading unless these behaviours are considered in the context of the true multidimensional nature of fitness. Submitted by Chris Thompson [christopher.thompson@manchester.ac.uk] ---------------------------------------------------------------------- Genetic control of morphogenesis in Dictyostelium William F. Loomis University of California San Diego, La Jolla, CA 92093 Developmental Biology, in press Cells grow, move, expand, shrink and die in the process of generating the characteristic shapes of organisms. Although the structures generated during development of the social amoeba Dictyostelium discoideum look nothing like the structures seen in metazoan embryogenesis, some of the morphogenetic processes used in their making are surprisingly similar. Recent advances in understanding the molecular basis for directed cell migration, cell type specific sorting, differential adhesion, secretion of matrix components, pattern formation, regulation and terminal differentiation are reviewed. Genes involved in Dictyostelium aggregation, slug formation, and culmination of fruiting bodies are discussed. Submitted by Bill Loomis [wloomis@ucsd.edu] ---------------------------------------------------------------------- Leaps and lulls in the developmental transcriptome of Dictyostelium discoideum Rafael David Rosengarten, Balaji Santhanam, Danny Fuller, Mariko Katoh-Kurasawa, William F. Loomis, Blaz Zupan, and Gad Shaulsky Department of Molecular and Human Genetics and Graduate Program in Structural and Computational Biology and Molecular Biophysics, Baylor College of Medicine Section of Cell and Developmental Biology, University of California San Diego Faculty of Computer and Information Science, University of Ljubljana BMC Genomics, accepted 26 March 2015 Background. Development of the soil amoeba Dictyostelium discoideum is triggered by starvation. When placed on a solid substrate, the starving solitary amoebae cease growth, communicate via extracellular cAMP, aggregate by tens of thousands and develop into multicellular organisms. Early phases of the developmental program are often studied in cells starved in suspension while cAMP is provided exogenously. Previous studies revealed massive shifts in the transcriptome under both developmental conditions and a close relationship between gene expression and morphogenesis, but were limited by the sampling frequency and the resolution of the methods. Results. Here, we combine the superior depth and specificity of RNA-seq-based analysis of mRNA abundance with high frequency sampling during filter development and cAMP pulsing in suspension. We found that the developmental transcriptome exhibits mostly gradual changes interspersed by a few instances of large shifts. For each time point we treated the entire transcriptome as single phenotype, and were able to characterize development as groups of similar time points separated by gaps. The grouped time points represented gradual changes in mRNA abundance, or molecular phenotype, and the gaps represented times during which many genes are differentially expressed rapidly, and thus the phenotype changes dramatically. Comparing development on solid substrate to development in suspension revealed that gene expression in filter developed cells lagged behind those treated with exogenous cAMP in suspension. The high sampling frequency revealed many genes whose regulation is reproducibly more complex than indicated by previous studies. Gene Ontology enrichment analysis suggested that the transition to multicellularity coincided with rapid accumulation of transcripts associated with DNA processes and mitosis. Later development included the up-regulation of organic signaling molecules and co-factor biosynthesis. We observed multiple instances of enrichment of oxidation-reduction and reactive oxygen related terms. Our analysis also demonstrated a high level of synchrony among the developing structures throughout development. Conclusions. Our data describe D. discoideum development as a series of coordinated cellular and multicellular activities. Coordination occurred within fields of aggregating cells and among multicellular bodies, such as mounds or migratory slugs that experience both cell-cell contact and various soluble signaling regimes. These time courses, sampled at the highest temporal resolution to date in this system, provide a comprehensive resource for studies of developmental gene expression. Submitted by Gad Shaulsky [gadi@bcm.edu] ============================================================== [End dictyNews, volume 41, number 7]