dictyNews Electronic Edition Volume 32, number 5 February 20, 2009 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 ========= Review: A Novel Function of Ethylene Aiko Amagai Department of Biomolecular Science, Graduate School of Life Sciences,  Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577, Japan Gene Regulation and Systems Biology, in press The cellular slime mold, Dictyostelium mucoroides-7 (Dm7) exhibits clear  dimorphism; macrocyst formation as a sexual process and sorocap formation  as an asexual process. These two life cycles are regulated by two regulators,  ethylene and cyclic AMP (cAMP). This is the first report demonstrating a  novel function of ethylene at the cellular level. That is, ethylene induces  a zygote formed by cell fusion and subsequent nuclear fusion. Recently, the  function of ethylene at the molecular level has been clarified as it induces  zygote formation through an enhanced expression of a novel gene, zyg1.  The signaling pathway for induction or inhibition of zygote formation is  now trying to be clarified focusing on the ZYG1 protein.   Submitted by: Aiko Amagai [aiamagai@mail.tains.tohoku.ac.jp] -------------------------------------------------------------------------------- Regulation of Dictyostelium morphogenesis by RapGAP3 Taeck J. Jeon, Susan Lee, Gerald Weeks, Richard A. Firtel Developmental Biology, in press Rap1 is a key regulator of cell adhesion and cell motility in Dictyostelium.   Here, we identify a Rap1-specific GAP protein (RapGAP3) and provide  evidence that Rap1 signaling regulates cell-cell adhesion and cell migration  within the multicellular organism.  RapGAP3 mediates the deactivation of Rap1  at the late mound stage of development and plays an important role in regulating  cell sorting during apical tip formation, when the anterior-posterior axis of the  organism is formed, by controlling cell-cell adhesion and cell migration. The  loss of RapGAP3 results in a severely altered morphogenesis of the multicellular  organism at the late mound stage.  Direct measurement of cell motility within  the mound shows that rapGAP3- cells have a reduced speed of movement and,  compared to wild-type cells, have a reduced motility towards the apex.   rapGAP3- cells exhibit some increased EDTA/EGTA sensitive cell-cell adhesion  at the late mound stage.  RapGAP3 transiently and rapidly translocates to  the cell cortex in response to chemoattractant stimulation, which is dependent  on F-actin polymerization.  We suggest that the altered morphogenesis and the  cell-sorting defect of rapGAP3- cells may result a reduced directional movement  of the mutant cells to the apex of the mound. Submitted by: Rick Firtel [rafirtel@ucsd.edu] -------------------------------------------------------------------------------- Targeting the actin-binding protein VASP to late endosomes induces the formation  of giant actin aggregates  Christian Schmauch, Susan Claussner, Hellmuth Zoeltzer, and Markus Maniak Abteilung Zellbiologie und CINSaT, Universitaet Kassel, Heinrich-Plett-Str. 40,  34132 Kassel, Germany Eur. J. Cell Biol., in press In vitro, the vasodilator-stimulated phosphoprotein (VASP) acts as a regulator  of actin filament assembly in many ways. In cells it localizes to sites where  actin is rapidly polymerized such as filopodia, lamellipodia, and focal adhesions.  We have mistargeted VASP to the surface of the late endosome in Dictyostelium  cells thereby inducing the formation of a dense actin aggregate which sequesters  various actin-binding proteins and endosomal components. Depletion of these  proteins from the cytoplasm leads to phenotypes mimicking the corresponding  knockout cells. Some properties of the actin aggregate are reminiscent of Hirano  bodies that are often observed in nerve tissue from patients suffering from  neurodegenerative diseases, opening the possibility that protein sequestration  contributes to neuronal malfunction. Submitted by: Markus Maniak [maiak@uni-kassel.de] ============================================================== [End dictyNews, volume 32, number 5]