dictyNews Electronic Edition Volume 36, number 2 Jan 21, 2011 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 ========= Nhe1 Is Essential For Potassium But Not Calcium Facilitation Of Cell Motility And The Monovalent Cation Requirement For Chemotactic Orientation In Dictyostelium discoideum Daniel F. Lusche, Deborah Wessels, Daniel E. Ryerson, and David R. Soll Eukaryotic Cell, in press In Dictyostelium discoideum, extracellular K+ or Ca++ at concentrations of 40 and 20 mM, respectively, facilitates motility in the absence or presence of a spatial gradient of chemoattractant. Facilitation results in maximum velocity, cellular elongation, persistent translocation, suppression of lateral pseudopod formation and myosin II localization in the posterior cortex. A lower threshold concentration of 15 mM K+ or Na, or 5 mM Ca++, is required for chemotactic orientation. Although the common buffer solutions used by D. discoideum researchers to study chemotaxis contain sufficient concentrations of cations for chemotactic orientation, the majority contain insufficient levels to facilitate motility. Here, it is demonstrated that Nhe1, a plasma membrane protein, is required for K+, but not Ca++, facilitation of cell motility, and for the lower K+, but not Ca++, requirement for chemotactic orientation. Submitted by Deb Wessels [deborah-wessels@uiowa.edu] -------------------------------------------------------------------------------- Cell-cycle checkpoint for transition from cell division to differentiation Yasuo Maeda Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan Develop. Growth Differ., in press (Review article) In general, growth and differentiation are mutually exclusive, but they are cooperatively regulated during the course of development. Thus, the process of a cellÕs transition from growth to differentiation is of general importance for the development of organisms, and terminally differentiated cells such as nerve cells never divide. Meanwhile, the growth rate speeds up when cells turn malignant. The cellular slime mold Dictyostelium discoideum grows and multiplies as long as nutrients are supplied, and its differentiation is triggered by starvation. A critical checkpoint (growth/differentiation transition or GDT point), from which cells start differentiating in response to starvation, has been precisely specified in the cell cycle of D. discoideum Ax-2 cells. Accordingly, integration of GDT pointŠspecific events with starvation-induced events is needed to understand the mechanism regulating GDTs. A variety of intercellular and intracellular signals are involved positively or negatively in the initiation of differentiation, making a series of cross-talks. As was expected from the presence of the GDT point, the cellÕs positioning in cell masses and subsequent cell-type choices occur depending on the cellÕs phase in the cell cycle at the onset of starvation. Since novel and multiple functions of mitochondria in various respects of development including the initiation of differentiation have been directly realized in Dictyostelium cells, they are also reviewed in this article. Submitted by Yasuo Maeda [kjygy352@ybb.ne.jp] -------------------------------------------------------------------------------- Ethylene as a potent inducer of sexual development Aiko Amagai DGD, in press (Review article) A novel and critical function of ethylene, a potent plant hormone, has been well documented in Dictyostelium, because it leads cells to the sexual development (macrocyst formation) by inducing zygote formation. Zygote formation (sexual cell fusion) and the subsequent nuclear fusion are the characteristic events occurring during macrocyst formation. A novel gene, zyg1 was found to be predominantly expressed during the sexual development, and its enforced expression actually induces zygote formation. As expected, the zygote inducer, ethylene enhances the expression of zyg1. Thus the function of ethylene has been verified at all of individual (macrocyst formation), cellular (zygote formation), and molecular levels (zyg1 expression). Based on our recent studies concerning the behavior and function of the zyg1 product (ZYG1 protein), the signal transduction pathways involved in zygote formation are proposed in this review. Submitted by: Aiko Amagai [aiamagai@mail.tains.tohoku.ac.jp] ============================================================== [End dictyNews, volume 36, number 2]