dictyNews

Electronic Edition

Volume 43, number 24

October 13, 2017



Please submit abstracts of your papers as soon as they have been

accepted for publication by sending them to [log in to unmask]

or by using the form at

http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit.



Back issues of dictyNews, the Dicty Reference database and other

useful information is available at dictyBase - http://dictybase.org.



Follow dictyBase on twitter:

http://twitter.com/dictybase





=========

Abstracts

=========





Retrotransposon domestication and control in Dictyostelium discoideum



Marek Malicki, Maro Iliopoulou† and Christian Hammann



Ribogenetics Biochemistry Lab, Department of Life Sciences and 

Chemistry, Jacobs University Bremen, Bremen, Germany

†present address: Wellcome Trust Centre for Human Genetics, University 

of Oxford, Oxford, United Kingdom





Frontiers in Microbiology, in press



Transposable elements, identified in all eukaryotes, are mobile genetic 

units that can change their genomic position. Transposons usually employ 

an excision and reintegration mechanism, by which they change position, 

but not copy number. In contrast, retrotransposons amplify via RNA 

intermediates, increasing their genomic copy number. Hence, they 

represent a particular threat to the structural and informational integrity of 

the invaded genome. The social amoeba Dictyostelium discoideum, 

model organism of the evolutionary Amoebozoa supergroup, features a 

haploid, gene-dense genome that offers limited space for damage-free 

transposition. Several of its contemporary retrotransposons display intrinsic 

integration preferences, for example by inserting next to transfer RNAs 

genes or other retroelements. Likely, any retrotransposons that invaded the 

genome of the amoeba in a non-directed manner were lost during evolution, 

as this would result in decreased fitness of the organism. Thus, the 

positional preference of the Dictyostelium retroelements might represent a 

domestication of the selfish elements. Likewise, the reduced danger of such 

domesticated transposable elements led to their accumulation, and they 

represent about 10% of the current genome of D. discoideum. To prevent 

the uncontrolled spreading of retrotransposons, the amoeba employs control 

mechanisms including RNA interference and heterochromatization. Here, we 

review TRE5-A, DIRS-1 and Skipper-1, as representatives of the three 

retrotransposon classes in D. discoideum, which make up 5.7 % of the 

Dictyostelium genome. We compile open questions with respect to their 

mobility and cellular regulation, and suggest strategies, how these questions 

might be addressed experimentally.





submitted by:  Christian Hammann [[log in to unmask]]

——————————————————————————————————————





The polymorphic proteins TgrB1 and TgrC1 function as a ligand-receptor 

pair in Dictyostelium allorecognition



Shigenori Hirose, Gong Chen, Adam Kuspa and Gad Shaulsky



Baylor College of Medicine, Houston, TX





Journal of Cell Science, accepted



Allorecognition is a key factor in Dictyostelium development and sociality. 

It is mediated by two polymorphic transmembrane proteins, TgrB1 and 

TgrC1, that contain extracellular immunoglobulin domains. TgrB1 and 

TgrC1 are necessary and sufficient for allorecognition and they carry out 

separate albeit overlapping functions in development, but their mechanism 

of action is unknown. Here we show that TgrB1 acts as a receptor and 

TgrC1 as its ligand in cooperative aggregation and differentiation. The 

proteins bind each other in a sequence-specific manner, TgrB1 exhibits a 

cell-autonomous function, and TgrC1 acts non-cell-autonomously. The 

TgrB1 cytoplasmic tail is essential for its function and it becomes 

phosphorylated upon association with TgrC1. Dominant mutations in TgrB1 

activate the receptor function and confer partial ligand independence. 

These roles in development and sociality suggests that allorecognition is 

critical in the integration of individual cells into a coherent organism.





submitted by: Gad Shaulsky  [[log in to unmask]]

==============================================================

[End dictyNews, volume 43, number 24]