dictyNews Electronic Edition Volume 26, number 5 February 17, 2006 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 ============= Analysis of a gene that is a potential target for the Dictyostelium STAT protein Dd-STATa and that encodes a protein homologous to the adducin head domain Ryota Aoshima1, 2, Rieko Hiraoka1, 2, Nao Shimada1, 2 and Takefumi Kawata1, 3 1 Department of Biology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan 2These authors contributed equally to this work. 3 Corresponding author Int. J. Dev. Biol., in press. A Dd-STATa-null mutant, which is defective in expression of a Dictyostelium homologue of the metazoan STAT (signal transducer and activators of transcription) proteins, fails to culminate and this phenotype correlates with the loss of expression of various prestalk (pst) genes. An EST clone, SSK395, encodes a close homologue of the adducin amino-terminal head domain and harbors a putative actin-binding domain. We fused promoter fragments of the cognate gene, ahhA (adducin head homologue A), to a lacZ reporter and determined their expression pattern. The proximal promoter region is necessary for the expression of ahhA at an early (pre-aggregative) stage of development and this expression is Dd-STATa independent. The distal promoter region is necessary for expression at later stages of development in pstA cells, of the slug, and in upper cup and pstAB cells during culmination. The distal region is partly Dd-STATa-dependent. The ahhA-null mutant develops almost normally until culmination, but it forms slanting culminants that tend to collapse on to the substratum. The mutant also occasionally forms fruiting bodies with swollen papillae and with constrictions in the prestalk region. The AhhA protein localizes to the stalk tube entrance and also to the upper cup cells and in cells at or near to the constricted region where an F-actin ring is localized. These findings suggest that Dd-STATa regulates culmination and may be necessary for straight downward elongation of the stalk, via the putative actin-binding protein AhhA. Submitted by: Takefumi Kawata [tkawata@bio.sci.toho-u.ac.jp] ----------------------------------------------------------------------------- Regulation of Dictyostelium prestalk-specific gene expression by a SHAQKY family MYB transcription factor Masashi Fukuzawa, Natasha V. Zhukovskaya, Yoko Yamada, Tsuyoshi Araki and Jeffrey G. Williams+ University of Dundee MSI/WTB Complex Dow Street Dundee DD1 5EH UK Development, in press PstA and pstO cells are the two major populations in the prestalk region of the Dictyostelium slug and DIF-1 is a low molecular weight signalling molecule that selectively induces pstO cell-specific gene expression. The two cell types are defined by their differential utilisation of spatially separated regions of the ecmA promoter. Additionally, there are anterior-like cells (ALC) scattered throughout the rear, prespore region of the slug. They, like the pstO cells, utilise a cap-site distal ecmA promoter segment termed the ecmO region. When multimerised, a 22nucleotide sub-segment of the ecmO region directs expression in pstA cells, pstO cells and ALC. It also directs DIF-inducible gene expression. The 22-mer was used to purify MybE, a protein with a single MYB DNA binding domain of a type previously found only in a large family of plant transcription factors. Slugs of a mybE null (mybE-) strain express an ecmAO:lacZ fusion gene (i.e. a reporter construct containing the ecmA and ecmO promoter regions) in pstA cells but there is little or no expression in pstO cells and ALC. The ecmA gene is not induced by DIF-1 in a mybE- strain. Thus MybE is necessary for DIF-1 responsiveness and for the correct differentiation of pstO cells and ALC. Submitted by: Jeff Williams [j.g.williams@dundee.ac.uk] ============================================================================== [End dictyNews, volume 26, number 5]