dictyNews

Electronic Edition

Volume 44, number 15

May 25, 2018



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Abstracts

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Genome sequencing and functional characterization of the non-pathogenic 

Klebsiella pneumoniae KpGe bacteria.



Lima WC, Pillonel T, Bertelli C, Ifrid E, Greub G, Cosson P.





Microbes Infect. 2018 May 10 [Epub ahead of print] PMID: 29753816



Klebsiella pneumoniae is an extensively studied human pathogen 

responsible for a wide variety of infections. Dictyostelium discoideum is 

a model host organism employed to study many facets of the complex 

interactions between phagocytic cells and bacteria. Historically, a non-

pathogenic strain of K. pneumoniae has been used to feed Dictyostelium 

amoebae, and more recently to study cellular mechanisms involved in 

bacterial recognition, ingestion and killing. Here we provide the full 

genome sequence and functional characterization of this non-pathogenic 

KpGe strain.





submitted by:  Wanessa de Lima [[log in to unmask]]

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The chemoattractant glorin is inactivated by ester cleavage during early 

multicellular development of Polysphondylium pallidum



Daniel Heinrich1, Robert Barnett2, Luke Tweedy3, Robert Insall3, Pierre 

Stallforth2, Thomas Winckler1*



1 Pharmaceutical Biology, Institute of Pharmacy, Friedrich Schiller University 

Jena, Germany

2 Junior Research Group ‘Chemistry of Microbial Communication’, Leibniz 

Institute for Natural Product Research and Infection Biology – Hans Knöll 

Institute, Jena, Germany

3 Cancer Research UK Beatson Institute, Glasgow, UK





ACS Chemical Biology, accepted



Among the amoebozoan species capable of forming fruiting bodies, the 

dictyostelid social amoebae stand out since they form true multicellular 

organisms by means of single cell aggregation. Upon food depletion, 

cells migrate across gradients of extracellular signals initiated by cells in 

aggregation centers. The model species that is widely used to study 

multicellular development of social amoebae, Dictyostelium discoideum, 

uses cyclic adenosine monophosphate (cAMP) as chemoattractant to 

coordinate aggregation. Molecular phylogeny studies suggested that 

social amoebae evolved in four major groups, of which groups 1 and 2 

are paraphyletic to groups 3 and 4. During early development intercellular 

communication with cAMP appears to be restricted to group 4 species. 

Cells of group 1 and 2 taxa do not respond chemotactically to extracellular 

cAMP and likely use a dipeptide chemoattractant known as glorin 

(N-propionyl-g-l-glutamyl-l-d-lactam-ethylester) to regulate aggregation. 

Directional migration of glorin-responsive cells requires the periodic 

breakdown of the chemoattractant. Here, we identified an extracellular 

enzymatic activity (glorinase) in the glorin-responsive group 2 taxon 

Polysphondylium pallidum leading to the inactivation of glorin. We 

determined the inactivation mechanism to proceed via hydrolytic ethyl 

ester cleavage of the g-glutamyl moiety of glorin. Synthetic glorinamide, in 

which the ethyl ester group was substituted by an ethyl amide group, had 

glorin-like biological activity but was resistant to degradation by glorinase. 

Our observations pave the way for future investigations toward an ancient 

eukaryotic chemotaxis system.





submitted by:  Thomas Winckler [[log in to unmask]]

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Global characterization of the Dicer-like protein DrnB roles in miRNA 

biogenesis in the social amoeba Dictyostelium discoideum



1Zhen Liao, 1Jonas Kjellin, 2,3Marc P. Hoeppner, 2Manfred Grabherr, 

1Fredrik Söderbom



1Department of Cell and Molecular Biology, Uppsala University, 

Uppsala, Sweden

2Department of Medical Biochemistry and Microbiology, Uppsala University, 

Uppsala, Sweden

3Present address: Christian-Albrechts-University of Kiel, Institute of Clinical 

Molecular Biology, Kiel, Germany





RNA Biology, accepted



Micro (mi)RNAs regulate gene expression in many eukaryotic organisms 

where they control diverse biological processes. Their biogenesis, from 

primary transcripts to mature miRNAs, have been extensively characterized 

in animals and plants, showing distinct differences between these 

phylogenetically distant groups of organisms. However, comparably little is 

known about miRNA biogenesis in organisms whose evolutionary position is 

placed in between plants and animals and/or in unicellular organisms. Here, 

we investigate miRNA maturation in the unicellular amoeba Dictyostelium 

discoideum, belonging to Amoebozoa, which branched out after plants but 

before animals. High-throughput sequencing of small RNAs and poly(A)-

selected RNAs demonstrated that the Dicer-like protein DrnB is required, and 

essentially specific, for global miRNA maturation in D. discoideum. Our 

RNA-seq data also showed that longer miRNA transcripts, generally preceded 

by a T-rich putative promoter motif, accumulate in a drnB knock-out strain. For 

two model miRNAs we defined the transcriptional start sites (TSSs) of primary 

(pri)-miRNAs and showed that they carry the RNA polymerase II specific 

m7G-cap. The generation of the 3’-ends of these pri-miRNAs differs, with 

pri-mir-1177 reading into the downstream gene, and pri-mir-1176 displaying a 

distinct end. This 3´-end is processed to shorter intermediates, stabilized in 

DrnB-depleted cells, of which some carry a short oligo(A)-tail. Furthermore, we 

identified 10 new miRNAs, all DrnB dependent and developmentally regulated. 

Thus, the miRNA machinery in D. discoideum shares features with both plants 

and animals, which is in agreement with its evolutionary position and perhaps 

also an adaptation to its complex lifestyle: unicellular growth and multicellular 

development.





submitted by:  Fredrik Söderbom  [[log in to unmask]]

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[End dictyNews, volume 44, number 15]