dictyNews Electronic Edition Volume 27, number 12 October 13, 2006 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. ============= Abstracts ============= A Phg2-Adrm1 pathway participates in the nutrient-controlled developmental response in Dictyostelium. Cherix, N., Froquet, R., Charette, S.J., Blanc, C., Letourneur, F., Cosson, P. Mol. Biol. Cell In press ictyostelium amoebae grow as single cells but upon starvation they initiate multicellular development. Phg2 was characterized previously as a kinase controlling cellular adhesion and the organization of the actin cytoskeleton. Here we report that Phg2 also plays a role during the transition between growth and multicellular development, as evidenced by the fact that phg2 mutant cells can initiate development even in the presence of nutrients. Even at low cell density and in rich medium, phg2 mutant cells express discoidin, one of the earliest pre-developmental markers. Complementation studies indicate that, in addition to the kinase domain, the core region of Phg2 is involved in the initiation of development. In this region, a small domain contiguous with a previously described ras-binding domain, was found to interact with the Dictyostelium ortholog of the mammalian adhesion-regulating molecule (ADRM1). In addition, adrm1 knockout cells also exhibit abnormal initiation of development. These results suggest that a Phg2-Adrm1 signaling pathway is involved in the control of the transition from growth to differentiation in Dictyostelium. Phg2 thus plays a dual role in the control of cellular adhesion and initiation of development. Submitted by: Pierre Cosson [Pierre.Cosson@medecine.unige.ch] ----------------------------------------------------------------------------- Molecular systematics of Dictyostelids: 5.8S rDNA and internal transcribed spacer region analyses. Maria Romeralo, Ricardo Escalante, Leandro Sastre and Carlos Lado Eukaryotic Cell, in press The variability and adaptability of the amoeba from the class Dictyosteliomycetes greatly complicate their systematics. The nucleotide sequences of the Ribosomal Internal Transcribed Spacers (ITS) and the 5.8 S rDNA gene has been determined for twenty eight isolates and shown their utility to discriminate between different species and genera. Submitted by: Leandro Sastre [lsastre@iib.uam.es] ----------------------------------------------------------------------------- Genetic evidence that the Acyl-CoA binding protein AcbA and the serine protease/ABC transporter TagA function together in Dictyostelium discoideum cell differentiation Matthew Cabral1,2, Christophe Anjard3, William F. Loomis3, and Adam Kuspa1,2 1Departments of Molecular and Human Genetics, 2Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, USA, 77030. 3 Center for Molecular Genetics, Division of Biological Sciences, University of California San Diego, La Jolla, CA 92093. Eukaryotic Cell, in press The acyl-CoA binding protein AcbA is cleaved to form a peptide (SDF-2) that coordinates spore encapsulation during the morphogenesis of Dictyostelium fruiting bodies. We present genetic evidence that the misspecification of cell types seen in mutants of the serine protease/ABC transporter TagA results from the loss of normal interactions with AcbA. Developmental phenotypes resulting from aberrant expression of the TagA protease domain, such as the formation of supernumerary tips on aggregates and the production of excess prestalk cells, are suppressed by null mutations in the acbA gene. Phenotypes resulting from the deletion of tagA, such as over-expresssion of the prestalk gene ecmB and the mis-expression of the prespore gene cotB in stalk cells, are also observed in acbA mutants. Moreover, tagA- mutants fail to produce SDF-2 during fruiting body morphogenesis, but are able to do so if they are stimulated with exogenous SDF-2. These results indicate that the developmental program depends on TagA and AcbA working in concert with each other during cell type differentiation and suggest that TagA is required for normal SDF-2 signaling during spore encapsulation. Submitted by: Adam Kuspa [akuspa@bcm.tmc.edu] ----------------------------------------------------------------------------- The monomeric clathrin assembly protein, AP180, regulates contractile vacuole size in Dictyostelium discoideum Irene Stavrou and Theresa J. O'Halloran University of Texas, Austin Mol. Biol. Cell In press AP180, one of many assembly proteins and adaptors for clathrin, stimulates the assembly of clathrin lattices on membranes, but its unique contribution to clathrin function remains elusive. In this study we identified the Dictyostelium discoideum ortholog of the adaptor protein AP180 and characterized a mutant strain carrying a deletion in this gene. Imaging GFP-labeled AP180 showed that it localized to punctae at the plasma membrane, the contractile vacuole and cytoplasm and associated with clathrin. AP180 null cells did not display defects characteristic of clathrin mutants, and continued to localize clathrin punctae on their plasma membrane and within the cytoplasm. However, like clathrin mutants, AP180 mutants, were osmosensitive. When immersed in water, AP180 null cells formed abnormally large contractile vacuoles. Furthermore, the cycle of expansion and contraction for contractile vacuoles in AP80 null cells was twice as long as that of wild type cells. Taken together, our results suggest that AP180 plays a unique role as a regulator of contractile vacuole morphology and activity in Dictyostelium. Submitted by: Terry O'Halloran [t.ohalloran@mail.utexas.edu] ============================================================================== [End dictyNews, volume 27, number 12]