dictyNews
Electronic Edition
Volume 43, number 17
August 4, 2017

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=========
Abstracts
=========


Dictyostelium discoideum: A model system for cell and developmental 
biology 


Sabateeshan Mathavarajah, Ana Flores, Robert J. Huber


Department of Biology, Trent University, Peterborough, Ontario, 
Canada


Current Protocols Essential Laboratory Techniques, in press

The social amoeba Dictyostelium discoideum has long served as a 
model system for studying fundamental processes in cell and 
developmental biology. This eukaryotic microbe is also recognized as 
a model organism for biomedical and human disease research since 
the genome encodes a large number of homologs of genes linked to 
human disease, such as those linked to cancer and neurodegeneration. 
Dictyostelium has a unique life cycle composed of a unicellular growth 
phase and a multicellular developmental phase that is induced by 
starvation. During its life cycle, Dictyostelium undergoes conserved 
cellular processes, including but not limited to, cell proliferation, 
phagocytosis, intercellular signalling, cell adhesion and motility, 
chemotaxis, and cell differentiation. The history of the organism, the 
resources available to researchers in the community, and the diverse 
ways that Dictyostelium is used in the contemporary research lab are 
discussed.


submitted by: Robert Huber [roberthuber@trentu.ca]
———————————————————————————————————————


Homeodomain-like DNA binding proteins control the haploid-to-diploid
transition in Dictyostelium

Katy Hedgethorne, Sebastian Eustermann, Ji-Chun Yang, Tom E. H. 
Ogden,David Neuhaus, Gareth Bloomfield

MRC Laboratory of Molecular Biology, Cambridge, UK.


Science Advances, in press

Homeodomain proteins control the developmental transition between 
the haploid and diploid phases in several eukaryotic lineages, but it is 
not known whether this reflects the ancestral condition or, instead, 
convergent evolution. We have characterized the mating-type locus of 
the amoebozoan Dictyostelium discoideum, which encodes two pairs of 
small proteins that determine the three mating types of this species; 
none of these proteins display recognizable homology to known families. 
We report that the nuclear magnetic resonance structures of two of them,
MatA and MatB, contain helix-turn-helix folds flanked by largely disordered 
amino- and carboxyl-terminal tails. This fold closely resembles that of 
homeodomain transcription factors, and, like those proteins, MatA and 
MatB each bind DNA characteristically using the third helix of their folded 
domains. By constructing chimeric versions containing parts of MatA and 
MatB, we demonstrate that the carboxyl-terminal tail, not the central DNA 
binding motif, confers mating specificity, providing mechanistic insight into 
how a third mating type might have originated. Finally, we show that these 
homeodomain-like proteins specify zygote function: Hemizygous diploids, 
formed in crosses between a wild-type strain and a mat null mutant, grow 
and differentiate identically to haploids. We propose that Dictyostelium 
MatA and MatB are divergent homeodomain proteins with a conserved 
function in triggering the haploid-to-diploid transition that can be traced 
back to the last common ancestor of eukaryotes.


submitted by: Gareth Bloomfield  [garethb@mrc-lmb.cam.ac.uk]
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[End dictyNews, volume 43, number 17]