dictyNews Electronic Edition Volume 43, number 7 April 7, 2017 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 ========= Does high relatedness promote cheater-free multicellularity in synthetic lifecycles? R. F. Inglis, E. Ryu, O. Asikhia, J. E. Strassmann & D. C. Queller Journal of Evolutionary Biology, in press The evolution of multicellularity is one of the key transitions in evolution and requires extreme levels of cooperation between cells. However, even when cells are genetically identical, noncooperative cheating mutants can arise that cause a breakdown in cooperation. How then, do multicellular organisms maintain cooperation between cells? A number of mechanisms that increase relatedness amongst cooperative cells have been implicated in the maintenance of cooperative multicellularity including single-cell bottle- necks and kin recognition. In this study, we explore how relatively simple biological processes such as growth and dispersal can act to increase related-ness and promote multicellular cooperation. Using experimental populations of pseudo- organisms, we found that manipulating growth and dispersal of clones of a social amoeba to create high levels of relatedness was sufficient to prevent the spread of cheating mutants. By contrast, cheaters were able to spread under low-relatedness conditions. Most surprisingly, we saw the largest increase in cheating mutants under an experimental treatment that should create intermediate levels of relatedness. This is because one of the factors raising relatedness, structured growth, also causes high vulnerability to growth rate cheaters. submitted by: Fredrik Inglis [inglis@wustl.edu] ——————————————————————————————————————— Evidence that differentiation-inducing factor-1 controls chemotaxis and cell differentiation, at least in part, via mitochondria in Dictyostelium discoideum. Yuzuru Kubohara*, Haruhisa Kikuchi, Van Hai Nguyen, Hidekazu Kuwayama, and Yoshiteru Oshima *Laboratory of Health and Life Science, Graduate School of Health and Sports Science, Juntendo University, Inzai, Chiba 270-1695, Japan Biology Open, in press Differentiation-inducing factor-1 (DIF-1) is an important regulator of cell differentiation and chemotaxis in the development of the cellular slime mold Dictyostelium discoideum. However, the entire signaling pathways downstream of DIF-1 remain to be elucidated. To characterize DIF-1 and its potential receptor(s), we synthesized two fluorescent derivatives of DIF-1, DIF-1-BODIPY and DIF-1-NBD, and investigated their biological activities and cellular localization. DIF-1-BODIPY (5 microM) and DIF-1 (2 nM) induced stalk cell differentiation in the DIF-deficient strain HM44 in the presence of cAMP, whereas DIF-1-NBD (5 microM) had no effect. Microscopic analyses revealed that the biologically active derivative, DIF-1-BODIPY, was incorporated by stalk cells at late stages of differentiation and was localized to mitochondria. The mitochondrial uncouplers CCCP (carbonyl cyanide m-chlorophenylhydrazone) at 25–50 nM and DNP (dinitrophenol) at 2.5–5 microM induced partial stalk cell differentiation in HM44 in the presence of cAMP. DIF-1-BODIPY (1–2 microM) and DIF-1 (10 nM), as well as CCCP and DNP, suppressed chemotaxis in the wild-type strain Ax2 in shallow cAMP gradients. These results suggest that DIF-1-BODIPY and DIF-1 induce stalk cell differentiation and modulate chemotaxis, at least in part, by disturbing mitochondrial activity. submitted by: Yuzuru Kubohara [ykuboha@juntendo.ac.jp] ——————————————————————————————————————— Production of Novel Bispyrone Metabolites in the Cellular Slime Mold Dictyostelium giganteum Induced by Zinc(II) Ion Van Hai Nguyen, Haruhisa Kikuchi, Hikaru Sasaki, Kyoichi Iizumi, Yuzuru Kubohara, Yoshiteru Oshima. Tetrahedron 2017, 73, 583-588; http://doi.org/10.1016/j.tet.2016.12.040 In this study, Zn2+ induced the production of two new bispyrone-type metabolites, dictyobispyrone B and E, in the cellular slime mold Dictyostelium giganteum. Their structures were proposed on the basis of spectroscopic analysis and confirmed by chemical synthesis. They possess a novel alpha,alpha-bispyrone skeleton modified with long carbon chains. Both could be formed from two different polyketide chains through a novel biosynthetic pathway. Our results indicate that cultivation of cellular slime molds in the presence of Zn2+ is a useful technique for discovering other structurally unique compounds. submitted by: Haruhisa Kikuchi [hal@mail.pharm.tohoku.ac.jp] ——————————————————————————————————————— TRE5-A retrotransposition profiling reveals putative RNA polymerase III transcription complex binding sites on the Dictyostelium extrachromosomal rDNA element Thomas Spaller1, Marco Groth2, Gernot Glöckner3, Thomas Winckler1 1 Pharmaceutical Biology, Institute of Pharmacy, University of Jena, Germany 2 Core Facility DNA Sequencing, Leibniz Institute for Age Research – Fritz Lipmann Institute, Jena, Germany 3 Institute for Biochemistry I, Medical Faculty, University of Cologne, Germany PLOS ONE, accepted The amoeba Dictyostelium discoideum has a haploid genome in which two thirds of the DNA encodes proteins. Consequently, the space available for selfish mobile elements to expand without excess damage to the host genome is limited. The non- long terminal repeat retrotransposon TRE5-A maintains an active population in the D. discoideum genome and apparently adapted to this gene-dense environment by targeting positions ~47 bp upstream of tRNA genes that are devoid of protein-coding regions. Because only ~24% of tRNA genes are associated with a TRE5-A element in the reference genome, we evaluated whether TRE5-A retrotransposition is limited to this subset of tRNA genes. We determined that a tagged TRE5-A element (TRE5-Absr) integrated at 384 of 405 tRNA genes, suggesting that expansion of the current natural TRE5-A population is not limited by the availability of targets. We further observed that TRE5-Absr targets the ribosomal 5S gene on the multicopy extrachromosomal DNA element that carries the ribosomal RNA genes, indicating that TRE5-A integration may extend to the entire RNA polymerase III (Pol III) transcriptome. We determined that both natural TRE5-A and cloned TRE5-Absr retrotranspose to locations on the extrachromosomal rDNA element that contain tRNA gene-typical A/B box promoter motifs without displaying any other tRNA gene context. Based on previous data suggesting that TRE5-A targets tRNA genes by locating Pol III transcription complexes, we propose that A/B box loci reflect Pol III transcription complex assembly sites that possess a function in the biology of the extrachromosomal rDNA element. submitted by: Thomas Winckler [t.winckler@uni-jena.de] ——————————————————————————————————————— Regulation of nucleosome positioning by a CHD Type III chromatin remodeler and its relationship to developmental gene expression in Dictyostelium. James L. Platt, Nicholas A. Kent, Alan R. Kimmel and Adrian J. Harwood (2017) Genome Research 27: 591-600; http://genome.cshlp.org/content/27/4/591.full Nucleosome placement and repositioning can direct transcription of individual genes; however, the precise interactions of these events are complex and largely unresolved at the whole-genome level. The Chromodomain-Helicase-DNA binding (CHD) Type III proteins are a subfamily of SWI2/SNF2 proteins that control nucleosome positioning and are associated with several complex human disorders, including CHARGE syndrome and autism. Type III CHDs are required for multicellular development of animals and Dictyostelium but are absent in plants and yeast. These CHDs can mediate nucleosome translocation in vitro, but their in vivo mechanism is unknown. Here, we use genome-wide analysis of nucleosome positioning and transcription profiling to investigate the in vivo relationship between nucleosome positioning and gene expression during development of wild-type (WT) Dictyostelium and mutant cells lacking ChdC, a Type III CHD protein ortholog. We demonstrate major nucleosome positional changes associated with developmental gene regulation in WT. Loss of chdC caused an increase of intragenic nucleosome spacing and misregulation of gene expression, affecting ~50% of the genes that are repositioned during WT development. These analyses demonstrate active nucleosome repositioning during Dictyostelium multicellular development, establish an in vivo function of CHD Type III chromatin remodeling proteins in this process, and reveal the detailed relationship between nucleosome positioning and gene regulation, as cells transition between developmental states. submitted by: Adrian Harwood [harwoodaj@cf.ac.uk] ============================================================== [End dictyNews, volume 43, number 7]