dictyNews Electronic Edition Volume 31, number 3 July 18, 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 ========= A new family of transcription factors Yoko Yamada+, Hong Yu Wang+, Masashi Fukuzawa, Geoffrey J. Barton and Jeffrey G. Williams + Contributed equally School of Life Sciences University of Dundee DD1 5EH U. K. Development, in press CudA, a nuclear protein required for Dictyostelium prespore-specific gene expression,  binds in vivo to the promoter of the cotC prespore gene. A 14nt region of the cotC promoter binds CudA in vitro and ECudA, an Entamoeba CudA homologue, also binds to this site. The CudA and ECudA DNA binding site contains a dyad and, consistent with a symmetrical binding site, CudA forms a homodimer in the yeast two hybrid system. Mutation of CudA binding sites within the cotC promoter reduces expression in prespore cells. The CudA and ECudA proteins share a 120 amino acid core of homology and clustered point mutations inserted in two highly conserved motifs within the ECudA core region decrease its specific DNA binding in vitro.  This region, the presumptive DNA binding domain, is similar in sequence to domains in two Arabidopsis proteins and one Oryza protein. Significantly, these are the only proteins in the two plant species that contain an SH2 domain. Such a structure, with a DNA binding domain located upstream of an SH2 domain, suggests that the plant proteins are orthologous to metazoan STATs. Consistent with this notion the DNA sequence of the CudA half binding site, GAA, is identical to metazoan STAT half-sites; although the relative positions of the two halves of the dyad are reversed. These results define a hitherto unrecognised class of transcription factor and suggest a model for the evolution of STATs and their DNA binding sites.   Submitted by: Jeff Williams [j.g.williams@dundee.ac.uk] -------------------------------------------------------------------------------- From drought sensing to developmental control: evolution of cyclic AMP signaling in social amoebas. Allyson V. Ritchie1, Saskia van Es2, Celine Fouquet3  and Pauline Schaap* College of Life Sciences, University of Dundee, UK. Molecular Biology and Evolution, in press Amoebas and other protists commonly encyst when faced with environmental stress. While little is known of the signalling pathways that mediate encystation, the analogous process of spore formation in Dictyostelid social amoebas is better understood. In Dictyostelium discoideum, secreted cyclic AMP (cAMP) mediates the aggregation of starving amoebas and induces the differentiation of prespore cells. Intracellular cAMP acting on cAMP-dependent protein kinase (PKA) triggers the maturation of spores and prevents their germination under the prevalent conditions of high osmolality in the spore head. The osmolyte-activated adenylate  cyclase, ACG, produces cAMP for prespore differentiation  and inhibition of  spore germination. To retrace the origin of ACG function, we investigated ACG gene conservation and function in species that span the dictyostelid phylogeny. ACG genes, osmolyte-activated ACG activity and osmo-regulation of spore germination were detected in species that represent the four major groups of Dictyostelia. Unlike the derived species D.discoideum, many basal Dictyostelia have retained the ancestral mechanism of encystation from solitary amoebas. In these species and in solitary amoebas, encystation is independently triggered by starvation or by high osmolality. Osmolyte-induced encystation was accompanied by an increase in cAMP and prevented by inhibition of PKA, indicating  that ACG and PKA activation mediate this response. We propose that high osmolality signals drought in soil amoebas and that developmental cAMP  signaling in the Dictyostelia has evolved from this stress response. Submitted by: Pauline Schaap [p.schaap@dundee.ac.uk] ============================================================== [End dictyNews, volume 31, number 3]