Dicty News Electronic Edition Volume 23, number 2 July 16, 2004 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 Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= Transcriptional Transitions During Dictyostelium Spore Germination Qikai Xu, Miroslava Ibarra, Dana Mahadeo, Chad Shaw, Eryong Huang, Adam Kuspa, David Cotter and Gad Shaulsky Eukaryotic Cell, in press Many protozoa form spores in response to adversity, so spore germination is a key process in their life cycle. Dictyostelium discoideum sporulate in response to starvation following a developmental program. Germination is characterized by two visible changes, spore swelling and emergence of amoeba from the spore capsule. Several studies have indicated that an additional process termed spore activation is also required, but the physiological changes that characterize the three phases are largely uncharacterized. We used microarrays to monitor global transcriptional transitions as a surrogate measure of the physiological changes that occur during germination. Using two independent methods to induce germination, we identified changes in mRNA levels that characterize the germination process rather than changes that resulted from the induction method. We found that germination is characterized by three transitions. The first transition occurs during activation, while the spores appear dormant, the largest transition occurs when swelling begins, and the third occurs when emergence begins. These findings indicate that activation and swelling are not passive occurrences, such as dilution of inhibitors or spore rehydration, but active processes that are accompanied by dramatic events of mRNA degradation and de-novo transcription. This finding confirms and extends earlier reports that genes such as celA are regulated during spore germination. We also found by mutation analysis that the unconventional myosin gene myoI, which is induced during early germination, plays a role in the maintenance of dormancy and in spore swelling. This finding suggests that some of the observed transcriptional changes are required for spore germination. Submitted by: Gad Shaulsky [gadi@bcm.tmc.edu] ----------------------------------------------------------------------------- The Size-complexity Rule J. T. Bonner EEB Department, Princeton University, Princeton, NJ 08544 Evolution, In press It is widely accepted that bigger entities have a greater division of labor than small ones and this is reflected in the fact that larger multicellular organisms have a corresponding increase in the number of their cell types. This rule is examined in some detail from very small organisms to large animals, and plants and societies. Compared to other size-related rules, the size-complexity rule is relatively rough and approximate, yet clearly it holds throughout the whole range of living organisms, as well as for societies. The relationship between size and complexity is analyzed by examining the effects of size increase and decrease: size increase requires an increase in complexity, while size decrease permits, and sometimes requires, a decrease in complexity. Conversely, an increase or decrease in complexity permits, but does not require changes in size. An especially compelling argument for the close relation between size and complexity can be found in size quorum sensing in very small multicellular organisms. Submitted by: John Bonner [jtbonner@Princeton.EDU] ============================================================================== [End Dicty News, volume 23, number 2]