dictyNews Electronic Edition Volume 34, number 17 June 4, 2010 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 ========= Developmental significance of cyanide-resistant respiration under stressed conditions: experiments in Dictyostelium cells Kei Kimura,1 Hidekazu Kuwayama,2 Aiko Amagai 3 and Yasuo Maeda1* 1Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Sendai 980-8578; 2Graduate School of Life and Environmental Sciences, University of Tsukuba, Tennoudai 1-1-1, Tsukuba-shi, 305-8572; and 3Department of Biomolecular Science, Graduate School of Life Sciences, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577, Japan Develop. Growth Differ., in press We have previously reported that benzohydroxamic acid (BHAM), a potent inhibitor of cyanide (CN)-resistant respiration mediated by alternative oxidase (AOX), induces formation of unique cell masses (i.e., stalk-like cells with a large vacuole and thick cell wall) in starved Dictyostelium cells. Unexpectedly, however, aox-null cells prepared by homologous recombination exhibited normal development under normal culture conditions on agar, indicating that BHAM-induced stalk formation is not solely attributable to inhibition of CN-resistant respiration. This also suggests that a series of pharmacological approaches in the field of life science has serious limitations. Under stress (e.g., in submerged culture), starved aox-null cells exhibited slightly delayed aggregation compared with parental Ax-2 cells; most cells remained as loose aggregates even after prolonged incubation. Also, the developmental defects of aox-null cells became more marked upon incubation for 30 min just after starvation in the presence of ≥1.75 mM H2O2. This seems to indicate that CN-resistant respiration could mitigate cellular damages through reactive oxygen species (ROS), because AOX has a potential role in reduction of ROS production. Starved aox-null cells did not develop in the presence of 5 mM KCN (which completely inhibited the conventional cytochrome-mediated respiration) and remained as non-aggregated single cells on agar even after prolonged incubation. Somewhat surprisingly, however, parental Ax-2 cells were found to develop normally, forming fruiting bodies even in the presence of 10 mM KCN. Taken together, these results suggest that CN-resistant respiration might compensate for the production of ATP via oxidative phosphorylation. Submitted by Yasuo Maeda [kjygy352@ybb.ne.jp] -------------------------------------------------------------------------------- An invitation to die: Initiators of sociality in a social amoeba become selfish spores by Jennie J. Kuzdzal-Fick, David C. Queller, and Joan E. Strassmann Department of Ecology and Evolutionary Biology, Rice University Biology Letters, in press Greater size and strength are common attributes of contest winners. Even in social insects with high cooperation, the right to reproduce falls to the well-fed queens rather than to poorly fed workers. In Dictyostelium discoideum, formerly solitary amoebae aggregate when faced with starvation, and some cells die to form a stalk which others ride up to reach a better location to sporulate. The first cells to starve have lower energy reserves than those that starve later, and previous studies have shown that the better-fed cells in a mix tend to form disproportionately more reproductive spores. Therefore, one might expect that the first cells to starve and initiate the social stage should act altruistically and form disproportionately more of the sterile stalk, thereby enticing other better-fed cells into joining the aggregate. This would resemble caste determination in social insects, where altruistic workers are typically fed less than reproductive queens. However, we show the opposite result holds: the first cells to starve become reproductive spores, presumably by gearing up for competition and outcompeting late starvers to become prespore first. These findings pose the interesting question of why others would join selfish organizers. Submitted by Jennie Kuzdzal-Fick [jkuzdzal@rice.edu] ============================================================== [End dictyNews, volume 34, number 17]