dictyNews
Electronic Edition
Volume 41, number 11
May 29, 2015

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


A deep coverage Dictyostelium discoideum genomic DNA library 
replicates stably in E. coli

Rafael D. Rosengarten, Pamela R. Beltran and Gad Shaulsky

Department of Molecular and Human Genetics Baylor College 
of Medicine, Houston, TX


Genomics, accepted for publication

The natural history of the amoeba Dictyostelium discoideum 
has inspired scientific inquiry for seventy-five years. A 
genetically tractable haploid eukaryote, D. discoideum appeals 
as a laboratory model as well. However, certain rote molecular 
genetic tasks, such as PCR and cloning, are difficult due to 
the AT-richness and low complexity of its genome. Here we 
report on the construction of a ~20 fold coverage D. discoideum 
genomic library in E. coli, cloning 4 – 10 kilobase partial 
restriction fragments into a linear vector. End-sequencing 
indicates that most clones map to the six chromosomes in an 
unbiased distribution. Over 70% of these clones contain at 
least one complete open reading frame. We demonstrate that 
individual clones and library composition are stable over 
multiple replication cycles. Our library will enable numerous 
molecular biological applications and the completion of 
additional species’ genome sequences, and suggests a path 
towards the long-elusive goal of genetic complementation.


Submitted by Gad Shaulsky [[log in to unmask]] 
----------------------------------------------------------------------


Secreted cyclic-di-GMP induces stalk cell differentiation in the 
eukaryote Dictyostelium discoideum

Minireview
Zhi-hui Chen and Pauline Schaap#

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


J. Bacteriol., in press

Cyclic-di-GMP is currently recognized as the most widely used 
intracellular signal molecule in prokaryotes, but roles in 
eukaryotes were only recently discovered. In the social amoeba 
Dictyostelium discoideum, c-di-GMP, produced by a prokaryote-type 
diguanylate cyclase, induces the differentiation of stalk cells, 
thereby enabling the formation of spore- bearing fruiting bodies. 
In this review, we summarize the currently known mechanisms that 
control the major life cycle transitions of Dictyostelium and focus 
particularly on the role of c-di-GMP in stalk formation. Stalk cell 
differentiation has characteristics of autophagic cell death, a 
process that also occurs in higher eukaryotes. We discuss the 
respective roles of c-di-GMP and of another signal molecule, DIF, 
in autophagic cell death in vitro and in stalk formation in vivo.


Submitted by Pauline Schaap [[log in to unmask]] 
----------------------------------------------------------------------


Temporal regulation of kin recognition maintains recognition-cue 
diversity and suppresses cheating

Hsing-I Ho and Gad Shaulsky

Department of Molecular and Human Genetics, Baylor College of 
Medicine, Houston, TX

Nature Communications, in press

Kin recognition, the ability to distinguish kin from non-kin, can 
facilitate cooperation between relatives. Evolutionary theory predicts 
that polymorphism in recognition cues, which is essential for effective 
recognition, would be unstable. Individuals carrying rare recognition 
cues would benefit less from social interactions than individuals with 
common cues, leading to loss of the genetic cue-diversity. We test 
this evolutionary hypothesis in Dictyostelium discoideum, which forms 
multicellular fruiting bodies by aggregation and utilizes two 
polymorphic membrane proteins to facilitate preferential cooperation. 
Surprisingly, we find that rare recognition variants are tolerated and 
maintain their frequencies among incompatible majority during 
development. Although the rare variants are initially excluded from the 
aggregates, they subsequently rejoin the aggregate and produce spores. 
Social cheating is also refrained in late development, thus limiting 
the cost of chimerism. Our results suggest a potential mechanism to 
sustain the evolutionary stability of kin recognition genes and to 
suppress cheating.


Submitted by Gad Shaulsky [[log in to unmask]] 
==============================================================
[End dictyNews, volume 41, number 11]