Muramoto Tetsuya, Kuwayama Hidekazu, Kobayashi Kumiko, Urushihara Hideko
Graduate School of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8572, Japan.
Dev Biol. 2007 May 1;305(1):77-89. doi: 10.1016/j.ydbio.2007.01.039. Epub 2007 Feb 7.
Solitary amoebae of Dictyostelium discoideum are frequently exposed to stressful conditions in nature, and their multicellular development is one response to environmental stress. Here we analyzed an aggregation stage abundant gene, krsA, homologous to human krs1 (kinase responsive to stress 1) to understand the mechanisms for the initiation of development and cell fate determination. The krsA- cells exhibited reduced viability under hyperosmotic conditions. They produced smaller aggregates on membrane filters and did not form aggregation streams on a plastic surface under submerged starvation conditions, but were normal in sexual development. During early asexual development, the expression of cAMP-related genes peaked earlier in the knockout mutants. Neither cAMP oscillation in starved cells nor an increase in the cAMP level following osmotic stress was observed in krsA-. The nuclear export signal, as well as the kinase domain, in KrsA was necessary for stream formation. These results strongly suggest that krsA is involved in cAMP relay, and that signaling pathways for multicellular development have evolved in unison with the stress response.
盘基网柄菌的单个变形虫在自然环境中经常面临压力条件，其多细胞发育是对环境压力的一种反应。在这里，我们分析了一个在聚集阶段大量表达的基因krsA，它与人类的krs1（应激反应激酶1）同源，以了解发育起始和细胞命运决定的机制。krsA基因缺失的细胞在高渗条件下活力降低。它们在膜滤器上形成的聚集体较小，并且在淹没饥饿条件下在塑料表面上不会形成聚集流，但在有性发育方面是正常的。在早期无性发育过程中，cAMP相关基因的表达在基因敲除突变体中达到峰值的时间更早。在krsA基因缺失的细胞中，未观察到饥饿细胞中的cAMP振荡以及渗透应激后cAMP水平的升高。KrsA中的核输出信号以及激酶结构域对于聚集流的形成是必需的。这些结果强烈表明krsA参与了cAMP信号传递，并且多细胞发育的信号通路与应激反应协同进化。
