dictyNews Electronic Edition Volume 41, number 19 September 4, 2015 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 ========= Allorecognition, via TgrB1 and TgrC1, mediates the transition from unicellularity to multicellularity in the social amoebae Dictyostelium discoideum Shigenori Hirose1, Balaji Santhanam2,3, Mariko Katoh-Kurosawa2, Gad Shaulsky2,3,#, and Adam Kuspa1,2,# 1 Verna and Marrs McLean Department of Biochemistry and Molecular Biology 2 Department of Molecular and Human Genetics 3 Structural and Computational Biology and Molecular Biophysics Program # Corresponding Authors Baylor College of Medicine, Houston, TX 77030 USA Accepted to “Development” SUMMARY The social amoeba Dictyostelium discoideum integrates into a multicellular organism when individual starving cells aggregate and form a mound. The cells then integrate into defined tissues and develop into a fruiting body that consists of a stalk and spores. Aggregation is initially orchestrated by waves of extracellular cyclic adenosine monophosphate (cAMP) and previous theory suggested that cAMP and other field-wide diffusible signals mediate tissue integration and terminal differentiation as well. Cooperation between cells depends on an allorecognition system comprised of the polymorphic adhesion proteins TgrB1 and TgrC1. Binding between compatible TgrB1 and TgrC1 variants ensures that non-matching cells segregate into distinct aggregates prior to terminal development. Here, we have embedded a small number of cells with incompatible allotypes within fields of developing cells with compatible allotypes. We found that compatibility of the allotype encoded by the tgrB1 and tgrC1 genes is required for tissue integration, as manifested in cell polarization, coordinated movement, and differentiation into prestalk and prespore cells. Our results show that the molecules that mediate allorecognition in D. discoideum also control the integration of individual cells into a unified developing organism and this acts as a gating step for multicellularity. Submitted by Adam Kuspa [akuspa@bcm.edu] ---------------------------------------------------------------------- Title: Dissecting the function of Atg1 complex in Dictyostelium autophagy reveals a connection with the pentose phosphate pathway enzyme transketolase Ana Mesquita, Luis C. Tábara, Oscar Martinez-Costa, Natalia Santos-Rodrigo, Olivier Vincent and Ricardo Escalante Open Biol. 2015 Aug;5(8). Abstract The network of protein-protein interactions of the Dictyostelium discoideum autophagy pathway was investigated by yeast two-hybrid screening of the conserved autophagic proteins Atg1 and Atg8. These analyses confirmed expected interactions described in other organisms and also identified novel interactors that highlight the complexity of autophagy regulation. The Atg1 kinase complex, an essential regulator of autophagy, was investigated in detail here. The composition of the Atg1 complex in Dictyostelium discoideum is more similar to mammalian cells than to Saccharomyces cerevisiae since, besides Atg13, it contains Atg101, a protein not conserved in this yeast. We found that Atg101 interacts with Atg13 and genetic disruption of these proteins in Dictyostelium leads to an early block in autophagy, although the severity of the developmental phenotype and the degree of autophagic block is higher in Atg13 deficient cells. We have also identified a protein containing zinc-finger B-box and FNIP motifs that interacts with Atg101. Disruption of this protein increases autophagic flux suggesting that it functions as a negative regulator of Atg101. We also describe the interaction of Atg1 kinase with the pentose phosphate pathway enzyme transketolase. We found changes in the activity of endogenous transketolase activity in strains lacking or overexpressing Atg1 suggesting the presence of an unsuspected regulatory pathway between autophagy and the pentose phosphate pathway in Dictyostelium that seems to be conserved in mammalian cells. Submitted by Ricardo Escalante [rescalante@iib.uam.es] ============================================================== [End dictyNews, volume 41, number 19]