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 dicty@northwestern.edu 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 [c.hammann@jacobs-university.de] —————————————————————————————————————— 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 [gadi@bcm.edu] ============================================================== [End dictyNews, volume 43, number 24]