dictyNews

Electronic Edition

Volume 46, number 13

May 15, 2020



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Abstracts

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Cold climate adaptation is a plausible cause for evolution of multicellular

sporulation in Dictyostelia



Hajara M. Lawal1, Christina Schilde1, Koryu Kin1, Matthew W. Brown3, 

John James1, Alan R Prescott2 and Pauline Schaap1*



1School of Life Sciences, University of Dundee, Dundee DD1 5EH, UK

2Dundee Imaging Facility, University of Dundee, Dundee DD1 5EH, UK

3Department of Biological Sciences, Mississippi State University, 

Mississippi State, MS, USA





Scientific Reports, in press



Unicellular protozoa that encyst individually upon starvation evolved at 

least eight times into organisms that instead form multicellular fruiting 

bodies with spores. The Dictyostelia are the largest and most complex 

group of such organisms. They can be subdivided into 4 major groups, 

with many species in groups 1-3 having additionally retained encystment. 

To understand fitness differences between spores and cysts, we 

measured long-term survival of spores and cysts under climate-mimicking 

conditions, investigated spore and cyst ultrastructure and related fitness 

characteristics to species ecology. We found that spores and cysts 

survived 22oC equally well, but that spores survived wet and dry frost 

better than cysts, with group 4 spores being most resilient. Spore walls

 consist of three layers and those of cysts of maximally two, while spores 

 were also more compacted than cysts, with group 4 spores being most

  compacted. Group 4 species were frequently isolated from arctic and 

  alpine zones, which was rarely the case for group 1-3 species. We 

  inferred a fossil-calibrated phylogeny of Dictyostelia, which showed that 

  its two major branches diverged 0.52 billion years ago, following several 

  global glaciations. Our results suggest that Dictyostelium multicellular 

  sporulation was a likely adaptation to a cold climate.





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

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Functional Characterisation of the Autophagy ATG12~5/16 complex in 

Dictyostelium discoideum



Malte Karow 1, Sarah Fischer 1, Susanne Meßling 1, Roman Konertz 

1, Jana Riehl 1, Qiuhong Xiong 2, Ramesh Rijal 3, Prerana Wagle 4, 

Christoph S. Clemen 5,6,7 and Ludwig Eichinger 1



1 Centre for Biochemistry, Institute of Biochemistry I, Medical Faculty, 

University of Cologne, 50931 Cologne, Germany

2 Institute of Biomedical Sciences, Shanxi University, No. 92 Wucheng 

Road, Taiyuan 030006, China

3 Department of Biology, Texas A&M University, College Station, 

TX 77843-3474, USA

4 Bioinformatics Core Facility, CECAD Research Center, University of 

Cologne, 50931 Cologne, Germany

5 Institute of Aerospace Medicine, German Aerospace Center (DLR), 

51147 Cologne, Germany

6 Center for Physiology and Pathophysiology, Institute of Vegetative 

Physiology, Medical Faculty,

University of Cologne, 50931 Cologne, Germany

7 Institute of Neuropathology, University Hospital Erlangen, Friedrich-

Alexander University Erlangen-Nürnberg, 91054 Erlangen, Germany





Cells, in press



Macroautophagy, a highly conserved and complex intracellular degradative 

pathway, involves more than 20 core autophagy (ATG) proteins, among them 

the hexameric ATG12~5/16complex, which is part of the essential ubiquitin-

like conjugation systems in autophagy. Dictyostelium discoideum atg5 single, 

atg5/12 double, and atg5/12/16 triple gene knock-out mutant strains displayed 

similar defects in the conjugation of ATG8 to phosphatidylethanolamine,

development, and cell viability upon nitrogen starvation. This implies that ATG5, 

12 and 16 act as a functional unit in canonical autophagy. Macropinocytosis of 

TRITC dextran and phagocytosis of yeast were significantly decreased in 

ATG5¯ and ATG5¯/12¯ and even further in ATG5¯/12¯/16¯ cells. In contrast, 

plaque growth on Klebsiella aerogenes was about twice as fast for ATG5¯ and 

ATG5¯/12¯/16¯ cells in comparison to AX2, but strongly decreased for ATG5¯/12¯ 

cells. Along this line, phagocytic uptake of Escherichia coli was significantly 

reduced in ATG5¯/12¯ cells, while no difference in uptake, but a strong increase 

in membrane association of E. coli, was seen for ATG5¯ and ATG5¯/12¯/16¯ 

cells. Proteasomal activity was also disturbed in a complex fashion, consistent 

with an inhibitory activity of ATG16 in the absence of ATG5 and/or ATG12. Our 

results confirm the essential function of the ATG12~5/16 complex in canonical 

autophagy, and furthermore are consistent with autophagy-independent 

functions of the complex and its individual components. They also strongly 

support the placement of autophagy upstream of the ubiquitin-proteasome 

system (UPS), as a fully functional UPS depends on autophagy.



submitted by:  Ludwig Eichinger   [[log in to unmask]]

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[End dictyNews, volume 46, number 13]