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 [fukuzawa@hirosaki-u.ac.jp]
———————————————————————————————————————


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 [p.schaap@dundee.ac.uk]
———————————————————————————————————————


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 [p.schaap@dundee.ac.uk]
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[End dictyNews, volume 42, number 17]