dictyNews Electronic Edition Volume 30, number 5 February 8, 2008 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 ========= An immediate-early gene, srsA: its involvement in the starvation response that initiates differentiation of Dictyostelium cells Kazunori Sasaki 1*, Soo-Cheon Chae 2, William F. Loomis 3, Negin Iranfar 3, Aiko Amagai 1 and Yasuo Maeda 1 1, Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan; 2, Department of Pathology, School of Medicine, Wonkwang University, Iksan, Chonbuk 570-749, South Korea; 3 Cell and Developmental Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA92093, USA3 *Present address: Department of Molecular Biology, Yokohama City University School of Medicine, 3-9 Fuku-ura, Kanazawa-ku, Yokohama 236-0004, Japan Differentiation, in press When nutrients are depleted, Dictyostelium cells undergo cell cycle-arrest and initiate a differentiation program for survival. We have found a novel gene, srsA, which is rapidly expressed in the first 5 min following the removal of nutrients and is turned off within an hour. This gene encodes a small protein with no significant similarity to previously characterized proteins. Disruption of srsA results in delayed expression of the early genes acaA and carA that encode adenylyl cyclase and the cAMP receptor necessary for chemotactic aggregation. Streaming is delayed several hours and the aggregates are larger than normal in the mutant strains. These phenotypes are cell-autonomous. Overexpression of srsA also results in delayed aggregation. Some of the slugs of the srsAOE strains showed stalked migration reminiscent of the slugs of the related species D. mucoroides. The terminal structures formed by srsAOE cells were grossly abnormal and contained very few viable spores. When cells over-expressing srsA were developed together with an excess of wild type cells, the fruiting bodies were still abnormal indicating that the mutant cells have a domineering effect on late development. These findings suggest that srsA may be involved in both the starvation response and late differentiation. Submitted by: Yasuo Maeda [ymaeda@mail.tains.tohoku.ac.jp] -------------------------------------------------------------------------------- Structural and functional studies of a family of Dictyostelium discoideum developmentally regulated, prestalk genes coding for small proteins Juan J: Vicente, María Galardi-Castilla, Ricardo Escalante and Leandro Sastre Instituto de Investigaciones Biomédicas, CSIC/UAM. C/ Arturo Duperier, 4. 28029 – Madrid. Spain BMC Microbiology, in press Background The social amoeba Dictyostelium discoideum executes a multicellular development program upon starvation. This morphogenetic process requires the differential regulation of a large number of genes and is coordinated by extracellular signals. The MADS-box transcription factor SrfA is required for several stages of development, including slug migration and spore terminal differentiation. Results Subtractive hybridization allowed the isolation of a gene, sigN (SrfA-induced gene N), that was dependent on the transcription factor SrfA for expression at the slug stage of development. Homology searches detected the existence of a large family of sigN-related genes in the Dictyostelium discoideum genome. The 13 most similar genes are grouped in two regions of chromosome 2 and have been named Group1 and Group2 sigN genes. The putative encoded proteins are 87-89 amino acids long. All these genes have a similar structure, composed of a first exon containing a 13 nucleotides long open reading frame and a second exon comprising the remaining of the putative coding region. The expression of these genes is induced at10 hours of development. Analyses of their promoter regions indicate that these genes are expressed in the prestalk region of developing structures. The addition of antibodies raised against SigN Group 2 proteins induced disintegration of multi-cellular structures at the mound stage of development. Conclusions A large family of genes coding for small proteins has been identified in D. discoideum. Two groups of very similar genes from this family have been shown to be specifically expressed in prestalk cells during development. Functional studies using antibodies raised against Group 2 SigN proteins indicate that these genes could play a role during multicellular development. Submitted by: Leandro Sastre [lsastre@iib.uam.es] ============================================================== [End dictyNews, volume 30, number 5]