Analysis of a homologue of the adducin head gene which is a potential target for the Dictyostelium STAT protein Dd-STATa.
A Dd-STATa-null mutant, which is defective in expression of a Dictyostelium homologue of the metazoan STAT (signal transducers 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.
Aoshima
Ryota
R
Department of Biology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan.
Hiraoka
Rieko
R
Shimada
Nao
N
Kawata
Takefumi
T
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002148:Calmodulin-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004023:Dictyostelium / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism* / Q000502:physiology; D050791:STAT Transcription Factors / Q000502:physiology*; D000099291:Adducins
D000199:Actins; D002148:Calmodulin-Binding Proteins; D015800:Protozoan Proteins; D050791:STAT Transcription Factors; D000099291:Adducins; C426583:STATa protein, Dictyostelium