dictyNews

Electronic Edition

Volume 44, number 12

April 20, 2018



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Abstracts

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Role of Inositol Polyphosphates in Programmed Cell Death in 

Dictyostelium discoideum and its Developmental Life Cycle 



Qudes Al-Anbaky1, 2, Zeiyad Al-karakooly1, Richard Connor1, 

Lisa Williams1, Azure Yarbrough1, John Bush1 and Nawab Ali1*



1 Department of Biology, University of Arkansas at Little Rock, Little 

Rock, AR, USA 

2 Department of Biology, University of Diyala, Baquba, Iraq. 



Address for Correspondence: 

Nawab Ali, Department of Biology, College of Arts, Letters and Sciences, 

University of Arkansas at Little Rock, 2801 S. University Avenue, Little 

Rock, AR 72204, USA.  





Molecular and Cellular Biochemistry, in press



Programmed cell death or apoptosis is a key developmental process 

that maintains tissue homeostasis in multicellular organisms. Inositol 

polyphosphates (InsPs) are key signaling molecules known to regulate 

a variety of cellular processes including apoptosis in such organisms. 

The signaling role of InsPs in unicellular organisms such as Dictyostelium 

discoideum (D. discoideum) is not well understood. We investigated 

whether InsPs also play any role in apoptosis in D. discoideum and 

whether InsPs mediated apoptosis follows mechanism similar to those 

present in higher multicellular eukaryotes. We measured known apoptotic 

markers in response to exogenously administered InsP6, the major InsPs 

in the cell. We found that InsP6 was able to cause cell death in 

D. discoideum cell culture in a dose- and time-dependent manner as 

determined by cytotoxicity assays. Fluorescence staining with acridine 

orange/ethidium bromide and flow cytometry results confirmed that the 

cell death in D. discoideum by InsP6 was due to apoptotic changes. Poly 

(ADP-ribose) expression, a known apoptotic marker used in D. discoideum, 

was also increased following InsP6 treatment suggesting a role for InsP6 

mediated apoptosis in this organism. InsP6 mediated cell death was 

accompanied by production of reactive oxygen species and a decrease 

in mitochondrial membrane potential. Additionally, we studied the effects 

of InsP6 on developmental life cycle of D. discoideum, the processes likely 

affected by apoptosis. In conclusion, our studies provide evidence that 

InsP6 mediated cell death process is conserved in D. discoideum and 

plays an important signaling role in its developmental life cycle.





submitted by:  Nawab Ali [[log in to unmask]]

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The transcription factor Spores Absent A is a PKA dependent inducer 

of Dictyostelium sporulation



Yoko Yamada1, Andrew Cassidy2 and Pauline Schaap1*



1School of Life Sciences and 2Tayside Centre for Genomic Analysis, 

University of Dundee, Dundee DD15EH, Angus, UK





Nature Scientific Reports, in press



Sporulation in Dictyostelium fruiting bodies evolved from amoebozoan 

encystation with both being induced by cAMP acting on PKA, but with 

downstream components still being unknown. Using tagged mutagenesis 

to find missing pathway components, we identified a sporeless mutant 

defective in a nuclear protein, SpaA. Expression of prespore genes was 

strongly reduced in spaA- cells, while expression of many spore stage 

genes was absent. Chromatin immunoprecipitation (ChIP) of a SpaA-YFP 

gene fusion showed that (pre)spore gene promoters bind directly to SpaA, 

identifying SpaA as a transcriptional regulator. SpaA dependent spore 

gene expression required PKA in vivo and was stimulated in vitro by the 

membrane-permeant PKA agonist 8Br-cAMP. The PKA agonist also 

promoted SpaA binding to (pre)spore promoters, placing SpaA 

downstream of PKA. Sequencing of SpaA-YFP ChIPed DNA fragments 

revealed that SpaA binds at least 117 (pre)spore promoters, including 

those of other transcription factors that activate some spore genes. 

These factors are not in turn required for spaA expression, identifying 

SpaA as the major trancriptional inducer of sporulation.





submitted by:  Pauline Schaap [[log in to unmask]]

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Encystation: the most prevalent and underinvestigated differentiation 

pathway of eukaryotes.

Review



Pauline Schaap and Christina Schilde



School of Life Sciences, University of Dundee, Dundee DD15EH, UK



Microbiology, in press



Not long ago protists were considered one of four eukaryote kingdoms, 

but recent gene-based phylogenies show that they contribute to all nine 

eukaryote subdomains. The former kingdoms of animals, plants and 

fungi are now relegated to lower ranks within subdomains. Most 

unicellular protists respond to adverse conditions by differentiating into 

dormant walled cysts. As cysts, they survive long periods of starvation, 

drought and other environmental threats, only to re-emerge when 

conditions improve. For protists pathogens, the resilience of their cysts 

can prevent successful treatment or eradication of the disease. In this 

context, effort has been directed towards understanding the molecular 

mechanisms that control encystation. We here firstly summarize the 

prevalence of encystation across protists and next focus on Amoebozoa, 

where most of the health related issues occur. We review current data 

on processes and genes involved in encystation of the obligate parasite 

Entamoeba histolytica and the opportunistic pathogen Acanthamoeba. 

We show how the cAMP mediated signalling pathway that controls spore 

and stalk cell encapsulation in Dictyostelium fruiting bodies could be 

retraced to a stress-induced pathway controlling encystation in solitary 

Amoebozoa. We highlight the conservation and prevalence of cAMP 

signalling genes in Amoebozoan genomes and the suprisingly large and 

varied repertoire of proteins for sensing and processing environmental 

signals in individual species.





submitted by:  Pauline Schaap [[log in to unmask]]

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[End dictyNews, volume 44, number 12]