dictyNews
Electronic Edition
Volume 44, number 4
February 2, 2018
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Abstracts
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Multiple roots of fruiting body formation in Amoebozoa
Falk Hillmann, Gillian Forbes, Silvia Novohradská, Iuliia Ferling,
Konstantin Riege, Marco Groth,Martin Westermann, Manja Marz,
Thomas Spaller, Thomas Winckler, Pauline Schaap,
Gernot Glöckner
Genome Biology and Evolution, evy011
https://doi.org/10.1093/gbe/evy011
Establishment of multicellularity represents a major transition
in eukaryote evolution. A subgroup of Amoebozoa, the
dictyosteliids, has evolved a relatively simple aggregative
multicellular stage resulting in a fruiting body supported by a
stalk. Protosteloid amoeba, which are scattered throughout
the amoebozoan tree, differ by producing only one or few
single stalked spores. Thus, one obvious difference in the
developmental cycle of protosteliids and dictyosteliids seems to
be the establishment of multicellularity.
To separate spore development from multicellular interactions
we compared the genome and transcriptome of a Protostelium
species (Protostelium aurantium var. fungivorum) with those of
social and solitary members of the Amoebozoa. During fruiting
body formation nearly 4000 genes, corresponding to specific
pathways required for differentiation processes, are upregulated.
A comparison with genes involved in the development of dictyosteliids
revealed conservation of more than 500 genes, but most of them are
also present in Acanthamoeba castellanii for which fruiting bodies
have not been documented. Moreover, expression regulation of
those genes differs between P. aurantiumand Dictyostelium
discoideum.
Within Amoebozoa differentiation to fruiting bodies is common,
but our current genome analysis suggests that protosteliids and
dictyosteliids used different routes to achieve this. Most remarkable
is both the large repertoire and diversity between species in genes
that mediate environmental sensing and signal processing. This
likely reflects an immense adaptability of the single cell stage
to varying environmental conditions. We surmise that this signalling
repertoire provided sufficient building blocks to accommodate the
relatively simple demands for cell-cell communication in the
early multicellular forms.
submitted by: Gernot Glöckner [[log in to unmask]]
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An individual-level selection model for the apparent altruism
exhibited by cellular slime moulds
Amotz Zahavi†, Keith D. Harris1, Vidyanand Nanjundiah2
1 Department of Zoology, Tel Aviv University, Tel Aviv 69978,
Israel
2 Centre for Human Genetics, BioTech Park, Electronic City
(Phase I) Bangalore 560100, India
(E-mails [log in to unmask],
[log in to unmask]; †Deceased)
Journal of Biosciences, accepted
In Dictyostelium discoideum, cells that become part of the stalk
or basal disc display behaviour which can interpreted as altruistic.
Atzmony et al. (1997) had hypothesised that the behaviour could
be the outcome of an adaptive strategy based on differing intrinsic
quality, meaning potential for survival and reproduction, followed
by intercellular competition among amoebae of differing qualities.
Low quality amoebae would have a poor chance of succeeding
in the competition to form spores; they could enhance their
chances of survival by adopting a presumptive stalk strategy.
Here we extend the hypothesis by making use of recent findings.
Our approach is based on the view that an evolutionary explanation
for the apparent altruism of stalk cells in D. discoideum must apply
broadly to other cellular slime moulds (CSMs) that exhibit stalk cell
death. Further, it must be capable of being modified to cover social
behaviour in CSMs with an extracellular stalk, as well as in
sorocarpic amoebae whose stalk cells are viable. With regard to
D. discoideum, we suggest that (a) differentiation-inducing factor
(DIF), thought of as a signal that inhibits amoebae from forming
spores and induces them to differentiate into basal disc cells, is
better viewed as a mediator of competition among post-aggregation
amoebae and (b) the products of the ‘recognition genes’ tgrB and
tgrC allow an amoeba to assess its quality relative to that of its
neighbours and move to a position within the aggregate that
optimises its reproductive fitness. From this perspective, all cells
behave in a manner that is ‘selfish’ rather than ‘altruistic’, albeit
with different expectations of success.
submitted by: Vidya Nanjundiah [[log in to unmask]]
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[End dictyNews, volume 44, number 4]
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