An immediate-early gene, srsA: its involvement in the starvation response that initiates differentiation of Dictyostelium cells.
When nutrients are depleted, Dictyostelium cells undergo cell cycle arrest and initiate a differentiation program for survival. We have found a novel gene, srsA, which is rapidly expressed in the first 5 min following the removal of nutrients and is turned off within an hour. This gene encodes a small protein with no significant similarity to previously characterized proteins. Disruption of srsA results in delayed expression of the early genes acaA and carA that encode adenylyl cyclase and the cAMP receptor necessary for chemotactic aggregation, respectively. Streaming is delayed several hours and the aggregates are larger than normal in the mutant strains. These phenotypes are cell-autonomous. Overexpression of srsA also results in delayed aggregation. Some of the slugs of the srsA(OE) strains showed stalked migration reminiscent of the slugs of the related species Dictyostelium mucoroides. The terminal structures formed by srsA(OE) cells were grossly abnormal and contained very few viable spores. When cells overexpressing srsA were developed together with an excess of wild-type cells, the fruiting bodies were still abnormal, indicating that the mutant cells have a dominant effect on late development. These findings suggest that srsA may be involved in both the starvation response and late differentiation.
Sasaki
Kazunori
K
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
Chae
Soo-Cheon
SC
Loomis
William F
WF
Iranfar
Negin
N
Amagai
Aiko
A
Maeda
Yasuo
Y
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation / Q000235:genetics*; D004023:Dictyostelium / Q000166:cytology* / Q000235:genetics* / Q000378:metabolism; D017781:Genes, Immediate-Early / Q000235:genetics*; D017125:Genes, Protozoan; D008969:Molecular Sequence Data; D009024:Morphogenesis; D010641:Phenotype; D015800:Protozoan Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D013217:Starvation / Q000235:genetics
D015800:Protozoan Proteins