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dictyNews Volume 31 Number 14
dictyNews
Electronic Edition
Volume 31, number 14
October 31, 2008
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.
Upon publication of your paper, please send strains and plamids to
the Dicty Stock Center. For more information see
http://dictybase.org/StockCenter/Deposit.html.
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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Clustering of VASP actively drives processive, WH2 domain-mediated actin
filament elongation
Dennis Breitsprecher (1), Antje K Kiesewetter (1), Joern Linkner (1),
Claus Urbanke (1), Guenter P Resch (2,3), J Victor Small (2) and Jan Faix (1)
1) Institute for Biophysical Chemistry, Hannover Medical School, Hannover,
Germany
2) Institute of Molecular Biotechnology, Austrian Academy of Sciences,
Vienna, Austria
3) Research Institute of Molecular Pathology, Vienna, Austria
EMBO J., in press
Vasodilator-stimulated phosphoprotein (VASP) is a key regulator of dynamic
actin structures like filopodia and lamellipodia, but its precise function in
their formation is controversial. Using in vitro TIRF microscopy, we show for
the first time that both human and Dictyostelium VASP are directly involved
in accelerating filament elongation by delivering monomeric actin to the
growing barbed end. In solution, DdVASP markedly accelerated actin filament
elongation in a concentration-dependent manner but was inhibited by low
concentrations of capping protein (CP). In striking contrast, VASP clustered
on functionalized beads switched to processive filament elongation that
became insensitive even to very high concentrations of CP. Supplemented
with the in vivo analysis of VASP mutants and an EM structure of the protein,
we propose a mechanism by which membrane-associated VASP oligomers
use their WH2 domains to effect both the tethering of actin filaments and their
processive elongation in sites of active actin assembly.
Submitted by: Jan Faix [faix@bpc.mh-hannover.de]
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Segregate or cooperate- a study of the interaction between two species
of Dictyostelium
Chandra N Jack, Julia G Ridgeway, Natasha J Mehdiabadi, Emily I Jones,
Tracy A Edwards, David C Queller and Joan E Strassmann
BMC Evolutionary Biology 2008, 8:293doi:10.1186/1471-2148-8-293
Background
A major challenge for evolutionary biology is explaining altruism,
particularly when it involves death of one party and occurs across species.
Chimeric fruiting bodies of D. discoideum and D. purpureum develop from
formerly independent amoebae, and some die to help others. Here we
examine co-aggregation between D. discoideum and D. purpureum,
determine its frequency, which party benefits, and the extent of fair play
in contribution to the altruistic caste.
Results
We mixed cells from both species in equal proportions, and then we analyzed
193 individual fruiting bodies, which always had either a D. discoideum or
D. purpureum morphology (D. discoideum- 96, D. purpureum- 97). Fifty
percent of the fruiting bodies that looked like D. discoideum and 23% of
the fruiting bodies that looked like D. purpureum were chimeric, though
the majority of cells in any given fruiting body belonged to one species
(D. discoideum fruiting bodies- 0.72+/-0.05, D. purpureum fruiting bodies-
0.71+/-0.06). Clearly, there is species level recognition occurring that
keeps the cells mostly separate. The number of fruiting bodies with the
D. discoideum morphology was 486+/-61 in the mix treatment compared to
225+/- 32 fruiting bodies when D. discoideum was alone. However, the number
of D. discoideum spores did not significantly decrease from 2.75e7 +/-1.29e7
spores in the controls to 2.06e7 +/-8.33e6 spores in the mix treatments.
D. purpureum fruiting body and spore production decreased from 719+/- 111
fruiting bodies and 5.81e7+/-1.26e7 spores to 394+/-111 fruiting bodies
and 9.75e6 +/-2.25e6 spores in mixes compared to when it was grown alone.
Conclusions
Cooperating amoebae are able to make larger fruiting bodies, which is
advantageous for migration and dispersal. However, when both species are
present D. discoideum contributes more than its fair share to the spores
but both suffer a cost in producing fewer spores per fruiting body.
Submitted by: Chandra Jack [chanj@rice.edu]
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[End dictyNews, volume 31, number 14]
