dictyNews Electronic Edition Volume 34, number 13 April 23, 2010 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 ========= The secreted proteome profile of developing Dictyostelium discoideum cells Deenadayalan Bakthavatsalam and Richard H.Gomer Rice University, Department of Biochemistry and Cell Biology, Houston, TX 77005. USA Proteomics, in press Dictyostelium discoideum is a unicellular eukaryote that, when starved, aggregates to form multicellular structures. In this report, we identified the proteins secreted by developing Dictyostelium cells using mass spectrometry based proteomics. A total of 349 different secreted proteins were identified, indicating that at least 2.6% of the 13600 predicted proteins in the Dictyostelium genome are secreted. Gene ontology (GO) analysis suggests that many of the secreted proteins are involved in protein and carbohydrate metabolism, and proteolysis. Submitted by Richard Gomer [rgomer@tamu.edu] -------------------------------------------------------------------------------- Preparation of an antibody that recognizes and neutralizes Dictyostelium differentiation-inducing factor-1 Yuzuru Kubohara*, Haruhisa Kikuchi, Koji Nakamura, Yusuke Matsuo, Yoshiteru Oshima *Institute for Molecular and Cellular Regulation (IMCR), Gunma University, Maebashi 371-8512, Japan. BBRC, in press In the development of the cellular slime mold Dictyostelium discoideum, the differentiation-inducing factor-1 (DIF-1; 1-(3,5-dichloro-2,6-dihydroxy-4- methoxyphenyl)hexan-1-one) plays an important role in the regulation of cell differentiation and chemotaxis; however, the cellular signaling systems involving DIF-1 remain to be elucidated. To obtain a probe for DIF-1, we synthesized a DIF derivative (DIF-1-NH2; 6-amino-1-(3,5-dichloro-2,6- dihydroxy-4-methoxyphenyl)hexan-1-one), and prepared an anti-DIF-1 antibody using a DIF-1-NH2-conjugated macromolecule as the immunogen. A 100-fold dilution of the antibody bound to DIF-1-NH2-conjugated resin, and this binding was inhibited by co-addition of 20 uM DIF-1 or DIF-1-NH2. In a monolayer culture of HM44 cells, a DIF-deficient D. discoideum strain, 0.5 nM exogenous DIF-1 induced stalk cell formation in ~60% of the cells; this induction was dose-dependently inhibited by the antibody (diluted 12.5- or 25-fold). Furthermore, this inhibition by the antibody was recovered by co-addition of 2.5 or10 nM DIF-1. The results indicate that the anti-DIF-1 antibody recognizes DIF-1 and neutralizes its function. Submitted by Yuzuru Kubohara [kubohara@showa.gunma-u.ac.jp] -------------------------------------------------------------------------------- The Onset of Collective Behavior in Social Amoebae Thomas Gregor1, Koichi Fujimoto2, Noritaka Masaki2 and Satoshi Sawai 1,2* 1Graduate School of Arts and Sciences, University of Tokyo, 2ERATO Complex Systems Biology Project, JST, Tokyo 153-8902, Japan *To whom correspondence should be addressed. Science, in press In the social amoebae Dictyostelium discoideum, periodic synthesis and release of extracellular cyclic AMP (cAMP) guides cell aggregation and commitment to form fruiting bodies. It is unclear whether these oscillations represent an intrinsic property of individual cells or if they only exist as a population-level phenomenon. Here we show by live-cell imaging of intact cell populations that pulses originate from a discrete location despite constant exchange of cells to and from the region. In a perfusion chamber, both isolated single cells and cell populations switch from quiescence to rhythmic activity depending on the level of extracellular cAMP. A quantitative analysis shows that stochastic pulsing of individual cells below the threshold concentration of extracellular cAMP plays a critical role in the onset of collective behavior. Submitted by Satoshi Sawai [cssawai@mail.ecc.u-tokyo.ac.jp] ============================================================== [End dictyNews, volume 34, number 13]