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dictyNews Volume 28 Number 02
dictyNews
Electronic Edition
Volume 28, number 2
January 19, 2007
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.
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Abstracts
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Exploiting new terrain: an advantage to sociality in the slime mold
Dictyostelium discoideum
Jennie J. Kuzdzal-Fick , Kevin R. Foster , David C. Queller , and
Joan E. Strassmann
Behavioral Ecology, in press
Advance Access published on January 8, 2007, DOI 10.1093/beheco/arl102.
Understanding the ecological benefits of social actions is central to
explaining the evolution of social behavior. The social amoeba Dictyostelium
discoideum has been well studied and is a model for social evolution and
development, but surprisingly little is known about its ecology. When
starving, thousands of the normally solitary amoebae aggregate to form a
differentiated multicellular organism known as a slug. The slug migrates
toward the soil surface where it metamorphoses into a fruiting body of hardy
spores held up by a dead stalk comprising about one-fifth of the cells.
Multicellularity in D. discoideum is thought to have evolved to lift the
spores above the hazards of the soil where spores can be picked up for
long-distance dispersal. Here, we show that multicellularity has another
advantage: local dispersal to new food sources. We find that cells shed by
D. discoideum slugs during migration consume and remove bacteria in the path
of the slug, although slugs themselves do not breakup. We also show that
slugs are adept at local dispersal by comparing migration of slugs with
migration of individual cells of the mutant, CAP2, which cannot aggregate
and so rely only on cellular movement. In particular, the solitary cells of
the aggregation mutant are unable to cross a soil barrier, easily crossed by
slugs. We propose that the exploitation of local food patches is an important
selective benefit favoring multicellular cooperation in D. discoideum.
Submitted by Jennie Kuzdzal-Fick [jkuzdzal@rice.edu]
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Vectors For Expression Of Proteins With Single Or Combinatorial Fluorescent
Protein And Tandem Affinity Purification Tags In Dictyostelium
Marcel Meima¤, Karin E. Weening and Pauline Schaap*
School of Life Sciences, University of Dundee, Dundee, DD15EH, UK
Protein Expression and Purification, in press.
We constructed a series of expression vectors for purification of native
proteins and protein complexes in Dictyostelium. Protein purification is
achieved by either a C-terminal or N-terminal fusion of the protein of choice
to the tandem affinity purification (TAP) tag. The TAP tag consists of a
protein A tag and a calmodulin binding peptide (CBP) and has been
successfully used for purification of native protein complexes from yeast
and animal cells. Protein expression is driven by the constitutive actin 15
promoter and the vectors optionally carry additional green- or yellow
fluorescent protein (GFP or YFP) tags for fusion at either a C- or N-terminal
location. Tandem affinity purification of native Dictyostelium protein
complexes was tested by using pArc-34, one of the members of the well
characterized Dictyostelium Arp2/3 complex, as bait. After denaturation and
SDS-PAGE separation of the pArc-34 associated proteins all members of the
Arp2/3 complex could be identified.
Submitted by Pauline Schaap [p.schaap@dundee.ac.uk]
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Identification and domain mapping of Dictyostelium discoideum type-1 protein
phosphatase inhibitor-2
Juliana M. Sousa-Canavez, Daniela Beton, Daniela C. Gonzalez-Kristeller
and Aline M. da Silva
Biochimie, in press
Protein phosphatase type-1 catalytic subunit (PP1c) does not exist freely
in the cell and its activity must be very strictly controlled. Several
protein inhibitors of PP1c have been described including the classical
mammalian inhibitor-1 (I-1) and inhibitor-2 (I-2). Association of these
inhibitors with PP1c appears to involve multiple contacts and in the case
of I-2 no less than five I-2 interaction subdomains have been proposed. In
this report, we provide both in vitro and in vivo evidence that the
Dictyostelium discoideum genome encodes a protein (DdI-2) that is an
ortholog of mammalian I-2 being the first PP1c interacting protein
characterized in this social amoeba. Despite the low overall sequence
similarity of DdI-2 with other I-2 sequences and its long N-terminal
extension, the five PP1c interaction motifs proposed for mammalian I-2
are reasonably conserved in the Dictyostelium ortholog. We demonstrate that
DdI-2 interacts with and inhibits D.discoideum PP1c (DdPP1c), which we have
previously characterized. Moreover, using yeast two-hybrid assays we show
that a stable interaction of DdI-2 with DdPP1c requires multiple contacts.
Submitted by: Juliana de Sousa-Canavez [jums@iq.usp.br]
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[End dictyNews, volume 28, number 2]
