Sasaki Kazunori, Chae Soo-Cheon, Loomis William F, Iranfar Negin, Amagai Aiko, Maeda Yasuo
Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan.
Differentiation. 2008 Dec;76(10):1093-103. doi: 10.1111/j.1432-0436.2008.00298.x. Epub 2008 Jul 30.
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.
当营养物质耗尽时，盘基网柄菌细胞会经历细胞周期停滞，并启动一个分化程序以存活下来。我们发现了一个新基因srsA，它在去除营养物质后的最初5分钟内迅速表达，并在一小时内关闭。该基因编码一种小蛋白，与先前已鉴定的蛋白没有明显的相似性。srsA的破坏导致早期基因acaA和carA的表达延迟，这两个基因分别编码腺苷酸环化酶和趋化聚集所需的cAMP受体。在突变菌株中，细胞流动延迟数小时，聚集体比正常的更大。这些表型是细胞自主的。srsA的过表达也会导致聚集延迟。srsA（OE）菌株的一些蛞蝓状幼体表现出有柄迁移，类似于相关物种毛霉状盘基网柄菌的蛞蝓状幼体。srsA（OE）细胞形成的终末结构严重异常，且含有极少的活孢子。当过量表达srsA的细胞与过量的野生型细胞一起发育时，子实体仍然异常，这表明突变细胞对后期发育具有显性作用。这些发现表明，srsA可能参与饥饿应答和后期分化。
