Dicty News Electronic Edition Volume 22, number 14 June 04, 2004 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 Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= Prespore-to-stalk conversion involves the production of a pathway-specific glycoprotein, wst25, in the cellular slime mould Dictyostelium discoideum Yuzuru Kubohara,* Akiko Arai, Katsunori Takahashi, Kohei Hosaka, Koji Okamoto Biosignal Research Center, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi 371-8512, Japan Biochem. Biophys. Res. Commun., In press. We have previously identified a stalk-specific wheat germ agglutinin (WGA)-binding protein, wst34, in the cellular slime mould Dictyostelium discoideum (Kubohara and Okamoto, Biochem. Cell Biol. 68, 699-704, 1990). Here, we found another stalk-specific WGA-binding protein, wst25, which was detected with two antisera that recognize wst34. Using the two marker proteins, we then analyzed and compared the pathways of prestalk-to-stalk maturation and prespore-to-stalk conversion in vitro and in vivo. Prestalk cells isolated from normally formed slugs can be converted to stalk cells (designated StI) in vitro with 8-bromo-cAMP (Br-cAMP), whereas prespore cells isolated from slugs can be converted to fully vacuolated stalk cells (designated StII) in vitro with Br-cAMP and DIF-1. During the process of prespore-to-stalk conversion, prespore-specific mRNAs, D19 and 2H3, disappeared rapidly, while prestalk-specific mRNAs, ecmA and ecmB, appeared at 2 h of incubation and increased thereafter. Most importantly, however, the StII cells thus formed were biochemically different from the StI cells originated from prestalk cells; that is, StI cells expressed wst34 but not wst25, while StII cells expressed wst25 but not wst34. When prespore cells isolated from slugs were allowed to develop on a substratum, they differentiated into spores and stalk cells and formed fruiting bodies, and the stalk cells formed from prespore cells in vivo expressed wst25 but not wst34. The present results indicate that there are two types of stalk cells, StI (prestalk-origin) and StII (prespore-origin), and that wst34 and wst25 are the specific markers for StI and StII, respectively. Submitted by: Yuzuru Kubohara [kubohara@showa.gunma-u.ac.jp] ----------------------------------------------------------------------------- A Demonstration of Pattern Formation Without Positional Information in Dictyostelium Christopher R. L. Thompson*, Stefanie Reichelt and Robert R. Kay MRC Laboratory of Molecular Biology, Hills Road, Cambridge, England, CB2 2QH *author for correspondence and present address: School of Biological Sciences, University of Manchester, Oxford Road, Manchester, England, M13 9PT Development Growth and Differentiation, in press Although positional information, conveyed by morphogen gradients, is a widely accepted way of forming patterns during development, an alternative method is conceivable, based on the intermingled differentiation of cells with different fates, followed by their sorting into discrete pattern elements. It has been proposed that Dictyostelium prestalk and prespore cells behave in this way at the mound stage of development. However, it has been difficult to conclusively demonstrate that they initially differentiate intermingled, because rapid cell movement within the mound makes it impossible to be sure where prestalk and prespore cells originate. We have taken a novel approach to address this problem by blocking cell movement at different stages in development, using the actin-depolymerizing drug, latrunculin-A. Prestalk and prespore cells differentiate with essentially normal efficiency and timing in such paralyzed structures. When movement is blocked sufficiently early, the major cell types all subsequently differentiate at scattered positions throughout the aggregate, and even in the streams leading into it. Our work strongly supports the idea that the prestalk/prespore pattern in Dictyostelium forms without positional information and demonstrate that latrunculin-A may provide a useful tool for the investigation of patterning in other organisms. Submitted by: Chris Thompson [christopher.thompson@man.ac.uk] =============================================================================== [End Dicty News, volume 22, number 14]