dictyNews
Electronic Edition
Volume 42, number 17
July 8, 2016
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Abstracts
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A novel, lineage-primed prestalk cell subtype involved in the
morphogenesis of D. discoideum
Satoshi Kuwana, Hiroshi Senoo, Satoshi Sawai, Masashi Fukuzawa
Developmental Biology, in press
Dictyostelium morphogenesis requires the tip, which acts as
an organizer and conducts orchestrated cell movement and cell
differentiation. At the slug stage the tip region contains prestalk A
(pstA) cells,which are usually recognized by their expression of
reporter constructs that utilize a fragment of the promoter of the
ecmA gene. Here, using the promoter region of the o-methyl
transferase 12 gene (omt12) to drive reporter expression, we
demonstrate the presence, also within the pstA region, of a novel
prestalk cell subtype: the pstVA cells. Surprisingly, a sub-population
of the vegetative cells express a pstVA: GFP marker and, sort out to
the tip, both when developing alone and when co-developed with an
excess of unmarked cells. The development of such a purified
GFP-marked population is greatly accelerated: by precocious cell
aggregation and tip formation with accompanying precocious
elevation of developmental gene transcription. We therefore
suggest that the tip contains at least two prestalk cell subtypes: the
developmentally-specified pstA cells and the lineage-primed pstVA
cells. It is presumably the pstVA cells that play the dominant role in
morphogenesis during the earlier stages of development. The basis
for the lineage priming is, however, unclear because we can find no
correlation between pstVA differentiation and nutrient status during
growth or cell cycle position at the time of starvation, the two known
determinants of probable cell fate.
submitted by: Masashi Fukuzawa [[log in to unmask]]
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The multicellularity genes of Dictyostelid social amoebas
Gernot Glöckner1,2, Hajara M. Lawal3, Marius Felder4,
Reema Singh3, Gail Singer3, Cornelis J. Weijer3, and
Pauline Schaap3*
1Institute of Biochemistry I, Medical Faculty, University of
Cologne, D-50931 Cologne, Germany,
2Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB),
D-12587 Berlin, Germany,
3School of Life Sciences, University of Dundee, DD15EH, Dundee, UK
4Leibniz Institute on Aging, D-07745 Jena, Germany
Nature Communications, in press
The evolution of multicellularity enabled specialization of cells, but
required novel signalling mechanisms for regulating cell differentiation.
Early multicellular organisms are mostly extinct and the origins of these
mechanisms are unknown. Here, using comparative genome and
transcriptome analysis across eight uni- and multicellular amoebozoan
genomes, we find that 80% of proteins essential for development of the
multicellular Dictyostelia are already present in their unicellular relatives.
This set is enriched in cytosolic and nuclear proteins and protein kinases.
The remaining 20%, unique to Dictyostelia, mostly consists of extracellularly
exposed and secreted proteins, with roles in sensing and recognition, while
several genes for synthesis of signals that induce cell-type specialisation
were acquired by lateral gene transfer. Across Dictyostelia, changes in gene
expression correspond more strongly with phenotypic innovation than
changes in protein functional domains. We conclude that the transition to
multicellularity required novel signals and sensors rather than novel signal
processing mechanisms.
submitted by: Pauline Schaap [[log in to unmask]]
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Evolution of developmental signalling in Dictyostelid social amoebas
Pauline Schaap
School of Life Sciences, University of Dundee, DD15EH Dundee, UK
Current Opinion in Genetics and Development, in press
Dictyostelia represent a tractable system to resolve the evolution
of cell-type specialization, with some taxa differentiating into spores
only, and other taxa with additionally one or up to four somatic cell
types. One of the latter forms, Dictyostelium discoideum, is a popular
model system for cell- and developmental biology with key signalling
pathways controlling cell-specialization being resolved recently. For
the most dominant pathways evolutionary origins were retraced to a
stress response in the unicellular ancestor, while modifications in the
ancestral pathway were associated with acquisition of multicellular
complexity. This review summarizes our current understanding of
developmental signalling in D.discoideum and its evolution.
submitted by: Pauline Schaap [[log in to unmask]]
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[End dictyNews, volume 42, number 17]
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