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dictyNews Volume 38 Number 16
dictyNews
Electronic Edition
Volume 38, number 16
June 29, 2012
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.
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Abstracts
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Mind the gap: a comparative study of migratory behavior in
social amoebae
Owen M. Gilbert, Jennie J. Kuzdzal-Fick, David C. Queller,
Joan E. Strassmann
Behavioral Ecology and Sociobiology, in press
Social amoebae aggregate to form a multicellular slug that
migrates some distance. Most species produce a stalk during
migration, but some do not. We show that D. giganteum, a
species that produces stalk during migration, is able to traverse
small gaps and utilize bacterial resources following gap traversal
by shedding live cells. In contrast, we found D. discoideum, a
species that does not produce stalk during migration, can
traverse gaps only when in the presence of other speciesÕ stalks,
or other thin filaments. These findings suggest production of
stalk during migration allows traversal of gaps, as commonly
occur in soil and leaf litter. Considering the functional
consequences of a stalked migration may be important for
explaining the evolutionary maintenance or loss of a stalked
migration.
Submitted by Owen Gilbert [owen.gilbert@gmail.com]
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Dictyostelium uses the prokaryote messenger c-di-GMP to trigger
stalk cell differentiation.
Zhi-hui Chen and Pauline Schaap*
College of Life Sciences, University of Dundee, Dundee DD15EH,
UK
Nature, in press
Cyclic di-(3Õ:5Õ)-guanosine monophosphate (c-di-GMP) is a major
prokaryote signalling intermediate, which is synthesized by
diguanylate cyclases and triggers sessility and biofilm formation.
We detected the first eukaryote diguanylate cyclases (DgcAs) in
all major groups of Dictyostelia. Upon food depletion,
Dictyostelium discoideum amoebas collect into aggregates, which
first transform into migrating slugs and next into sessile fruiting
structures. These structures consist of a spherical spore mass
that is supported by a column of stalk cells and a basal disk. A
polyketide, DIF-1, was isolated earlier, which induces stalk-like
cells in vitro. However, its role in vivo proved recently to be
restricted to basal disk formation. Here we show that Dictyostelium
DgcA produces c-di-GMP as the morphogen responsible for stalk
cell differentiation. D.discoideum DgcA synthesized c-di-GMP in
a GTP-dependent manner and was expressed at the slug tip, the
site of stalk cell differentiation. Disruption of the DgcA gene
blocked the transition from slug migration to fructification and the
expression of stalk genes. Fructification and stalk formation were
restored by exposing dgca- slugs to wild-type secretion products
or to c-di-GMP. Moreover, c-di-GMP, but not c-di-AMP, induced
stalk gene expression in dilute cell monolayers. Apart from
identifying the long elusive stalk-inducing morphogen, our work
also identifies the first role for c-di-GMP in eukaryotes.
Submitted by Pauline Schaap [p.schaap@dundee.ac.uk]
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Structured growth and genetic drift raise relatedness in the social
amoeba Dictyostelium discoideum.
Neil J. Buttery(1), Chandra N. Jack(2), Boahemaa Adu-Oppong(1),
Kate T. Snyder(3), Christopher R.L. Thompson(4), David C. Queller(1)
and Joan E. Strassmann(1)
(1) Department of Biology, Campus Box 1137, Washington University
in Saint Louis, One Brookings Drive, Saint Louis, Missouri, USA
(2) Department of Bioengineering, Rice University, 6100 Main Street,
Houston, Texas, USA
(3) Department of Ecology and Evolution, Rice University, 6100
Main Street, Houston, Texas, USA
(4) Faculty of Life Sciences, University of Manchester,
Oxford Road, Manchester, UK
Biology Letters, in press
One condition for the evolution of altruism is genetic relatedness
between altruist and beneficiary, often achieved through active kin
recognition. Here we investigate the power of a passive process
resulting from genetic drift during population growth in the social
amoeba Dictyostelium discoideum. We put labelled and unlabelled
cells of the same clone in the centre of a plate, and allowed them
to proliferate outward. Zones formed by genetic drift, due to the
small population of actively growing cells at the colony edge. We
also found that single cells could form zones of high relatedness.
Relatedness increased at a significantly higher rate when food
was in short supply. This study shows that relatedness can be
significantly elevated before the social stage without a small
founding population size or recognition mechanism.
Submitted by Neil Buttery [buttery@wustl.edu]
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Innate Non_Specific Cell Substratum Adhesion
Loomis, W.F., Fuller, D., Gutierrez, E., Groisman, A.,
and Rappel, W-J.
Section of Cell and Developmental Biology, Division of Biological Sciences,
Department of Physics, Center for Theoretical Biological Physics
University of California, San Diego , La Jolla, CA
PLoS ONE, in press
Adhesion of motile cells to solid surfaces is necessary to transmit forces
required for propulsion. Unlike mammalian cells, Dictyostelium cells do
not make integrin mediated focal adhesions. Nevertheless, they can
move rapidly on both hydrophobic and hydrophilic surfaces. We have
found that adhesion to such surfaces can be inhibited by addition of
sugars or amino acids to the buffer. Treating whole cells
with _-mannosidase to cleave surface oligosaccharides also reduces
adhesion. The results indicate that adhesion of these cells is mediated
by van der Waals attraction of their surface glycoproteins to the
underlying substratum. Since glycoproteins are prevalent components
of the surface of most cells, innate adhesion may be a common
cellular property that has been overlooked.
Submitted by Bill Loomis [wloomis@ucsd.edu]
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[End dictyNews, volume 38, number 16]
