dictyNews Volume 26 Number 05

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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 
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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] 
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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] 
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[End dictyNews, volume 26, number 5]