dictyNews

Electronic Edition

Volume 45, number 28

November 1, 2019



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Abstracts

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The life cycle of Dictyostelium discoideum is accelerated via MAP 

kinase cascade by a culture extract produced by a synthetic 

microbial consortium



Hidekazu Kuwayama and Toru Higashinakagawa





Journal of Molecular Microbiology and Biotechnology, in press



A cellular slime mold, Dictyostelium discoideum, is an amoeboid 

organism that has unique life cycle consisting of distinctly separated 

vegetative and developmental phases. Thus, this organism presents 

a rare opportunity in which to examine the effects of bioactive 

substances on separate cellular activities. In this research, we 

investigated the effect of a culture extract, termed EMXG, produced 

by a synthetic microbial consortium. EMXG promoted proliferative 

response of amoeba cells. It further accelerated the developmental 

phase, leading to the preferred fruiting body formation from fewer 

cells. Furthermore, EMXG modulated biological rhythm of this 

organism, that is, interval of oscillation of cAMP level observed in 

suspension starvation was significantly shortened. Concomitantly, 

the level of ERKB, a MAP kinase, was found to oscillate in a similar 

fashion to that of cAMP. Additionally, ErkB deficient mutant amoeboid 

cells did not respond to proliferative stimulation by EMXG. These lines 

of evidence point to a likelihood that MAP kinase cascade is involved, 

and further that ErkB could be the molecular target of EMXG. 





submitted by:  Hidekazu Kuwayama  [[log in to unmask]]

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Mammals and Dictyostelium rictor mutations swapping reveals two 

essential Gly residues for mTORC2 activity and integrity



Barbara Pergolizzi, Cristina Panuzzo, M. Shahzad Ali, Marco Lo 

Iacono, Chiara Levra Levron, Luca Ponzone, Marta Prelli, Daniela 

Cilloni, Enzo Calautti, Salvatore Bozzaro, Enrico Bracco





Journal of Cell Science 2019 : jcs.236505 doi: 10.1242/jcs.236505 



mTORC2 regulates a variety of vital cellular processes, and its 

aberrant functioning is often associated with various diseases. 

Rictor is a peculiar and distinguishing mTORC2 component playing 

a pivotal role in controlling its assembly and activity. Among living 

organisms Rictor is conserved from unicellular eukaryotes to 

metazoan. We replaced two distinct, but conserved, glycines in 

both the Dictyostelium piaA gene and its human ortholog, rictor. 

The two conserved residues are spaced by approximately 50 

aminoacids and both are embedded within a conserved region 

falling in between the Ras-GEFN2 and Rictor_V domains. The 

effects of point mutations on the mTORC2 activity and integrity 

were assessed by biochemical and functional assays.In both cases, 

the reciprocal exchange between mammals and Dictyostelium 

rictor and piaA gene point mutations impaired mTORC2 activity 

and integrity.Our data indicate that the two Gly residues are essential 

for the maintenance of mTORC2 activity and integrity in organisms 

that appear to be distantly related, suggesting a primeval role in the 

assembly and proper TOR complex 2 functioning.





submitted by:  Barbara Pergolizzi  [[log in to unmask]]

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Evolution of multicellularity in the Dictyostelia



Yoshinori Kawabe, Qingyou Du, Christina Schilde and Pauline Schaap*



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





International Journal of Developmental Biology, in press



The well-orchestrated multicellular life cycle of Dictyostelium discoideum 

has fascinated biologists for over a century. Self-organisation of its 

amoebas into aggregates, migrating slugs and fruiting structures by 

pulsatile cAMP signalling and their ability to follow separate differentiation 

pathways in well-regulated proportions continue to be topics under 

investigation. A striking aspect of D. discoideum development is the 

recurrent use of cAMP as chemoattractant, differentiation inducing signal 

and second messenger for other signals that control the developmental 

programme. D. discoideum is one of >150 species of Dictyostelia and 

aggregative life styles similar to those of Dictyostelia evolved many times 

in eukaryotes. Here we review experimental studies investigating how 

phenotypic complexity and cAMP signalling co-evolved in Dictyostelia. 

In addition, we summarize comparative genomic studies of multicellular 

Dictyostelia and unicellular Amoebozoa aimed to identify evolutionary 

conservation and change in all genes known to be essential for 

D. discoideum development.





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

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Phylogeny-wide conservation and change in developmental expression, 

cell-type specificity and functional domains of the transcriptional 

regulators of social amoebas



Gillian Forbes, Zhi-hui Chen, Koryu Kin, Hajara M. Lawal, Christina 

Schilde, Yoko Yamada and Pauline Schaap*



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





BMC Genomics, in press



Background: Dictyostelid social amoebas self-organize into fruiting 

bodies, consisting of spores and up to four supporting cell types in the 

phenotypically most complex taxon group 4. High quality genomes and 

stage- and cell-type specific transcriptomes are available for representative 

species of each of the four taxon groups. To understand how evolution of 

gene regulation in Dictyostelia contributed to evolution of phenotypic 

complexity, we analysed conservation and change in abundance, 

functional domain architecture and developmental regulation of their 

transcription factors (TFs).  



Results: We detected 440 sequence-specific TFs across 33 families, 

of which 68% were upregulated in multicellular development and about 

half conserved throughout Dictyostelia. Prespore cells expressed two 

times more TFs than prestalk cells, but stalk cells expressed more TFs 

than spores, suggesting that gene expression events that define spores 

occur earlier than those that define stalk cells. Changes in TF 

developmental expression, but not in TF abundance or functional 

domains occurred more frequently between group 4 and groups 1-3, 

than between the more distant branches formed by groups 1+2 and 3+4. 



Conclusions: Phenotypic innovation is correlated with changes in TF 

regulation, rather than functional domain- or TF acquisition.  The function 

of only 34 TFs is known. Of 12 TFs essential for cell differentiation, 9 are 

expressed in the cell type for which they are required. The information 

acquired here on conserved cell type specifity of 120 additional TFs can 

effectively guide further functional analysis, while observed evolutionary 

change in TF developmental expression may highlight how genotypic 

change caused phenotypic innovation.





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

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Cytokinin detection during the Dictyostelium discoideum life cycle:

Profiles are dynamic and can affect cell growth and spore germination



Megan M. Aoki 1*,  Anna B. Kisiala 1, Shaojun Li 2, Naomi L. Stock 3, 

Craig R. Brunetti 1, Robert J. Huber 1 and R. J. Neil Emery 1



1 Department of Biology, Trent University, Peterborough, Ontario 

2 Noblegen, Peterborough, Ontario, Canada

3 Water Quality Centre, Trent University, Peterborough, Ontario 





Biomolecules, accepted



Cytokinins (CKs) are a family of evolutionarily conserved growth regulating 

hormones. While CKs are well-characterized in plant systems, these 

N6-substituted adenine derivatives are found in a variety of organisms 

beyond plants, including bacteria, fungi, mammals, and the social amoeba, 

Dictyostelium discoideum. Within Dicytostelium, CKs have only been studied 

in the late developmental stages of the life cycle, where they promote spore 

encapsulation and dormancy. In this study, we used ultra high-performance 

liquid chromatography-positive electrospray ionization-high resolution tandem 

mass spectrometry (UHPLC-(ESI+)-HRMS/MS) to profile CKs during the 

Dictyostelium life cycle: growth, aggregation, mound, slug, fruiting body, and 

germination. Comprehensive profiling revealed that Dictyostelium produces 

6 CK forms (cis-Zeatin (cZ), discadenine (DA), N6-isopentenyladenine (iP), 

N6-isopentenyladenine-9-riboside (iPR), N6-isopentenyladenine-9-riboside-

5’ phosphate (iPRP), and 2-methylthio-N6-isopentenyladenine (2MeSiP)) in 

varying abundance across the sampled life cycle stages, thus laying the 

foundation for the CK biosynthesis pathway to be defined in this organism. 

Interestingly, iP-type CKs were the most dominant CK analytes detected 

during growth and aggregation. Exogenous treatment of AX3 cells with 

various CK types revealed that iP was the only CK to promote the proliferation 

of cells in culture. In support of previous studies, metabolomics data revealed 

that discadenine (DA) is one of the most significantly upregulated small 

molecules during Dictyostelium development, and our data indicates that total 

CK levels are highest during germination. While much remains to be explored 

in Dictyostelium, this research offers new insight into the nature of CK 

biosynthesis, secretion, and function during Dictyostelium growth, 

development, and spore germination.





submitted by: Robert Huber [[log in to unmask]]

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[End dictyNews, volume 45, number 28]