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dictyNews Volume 22 Number 14
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.
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Abstracts
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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]
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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]
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[End Dicty News, volume 22, number 14]
