Rasmussen Anders A, Søgaard-Andersen Lotte
Department of Biochemistry and Molecular Biology, University of Southern Denmark Odense, 5230 Odense M, Denmark.
J Bacteriol. 2003 Sep;185(18):5452-64. doi: 10.1128/JB.185.18.5452-5464.2003.
In response to starvation, Myxococcus xanthus initiates a developmental program that results in the formation of spore-filled multicellular fruiting bodies. Fruiting body formation depends on the temporal and spatial coordination of aggregation and sporulation. These two processes are induced by the cell surface-associated C signal, with aggregation being induced after 6 h and sporulation being induced once cells have completed the aggregation process. We report the identification of TodK, a putative histidine protein kinase of two-component regulatory systems that is important for the correct timing of aggregation and sporulation. Loss of TodK function results in early aggregation and early, as well as increased levels of, sporulation. Transcription of todK decreases 10-fold in response to starvation independently of the stringent response. Loss of TodK function specifically results in increased expression of a subset of C-signal-dependent genes. Accelerated development in a todK mutant depends on the known components in the C-signal transduction pathway. TodK is not important for synthesis of the C signal. From these results we suggest that TodK is part of a signal transduction system which converges on the C-signal transduction pathway to negatively regulate aggregation, sporulation, and the expression of a subset of C-signal-dependent genes. TodK and the SdeK histidine protein kinase, which is part of a signal transduction system that converges on the C-signal transduction pathway to stimulate aggregation, sporulation, and C-signal-dependent gene expression, act in independent genetic pathways. We suggest that the signal transduction pathways defined by TodK and SdeK act in concert with the C-signal transduction pathway to control the timing of aggregation and sporulation.
作为对饥饿的响应，黄色黏球菌启动一个发育程序，最终形成充满孢子的多细胞子实体。子实体的形成取决于聚集和孢子形成在时间和空间上的协调。这两个过程由细胞表面相关的C信号诱导，聚集在6小时后被诱导，而孢子形成在细胞完成聚集过程后被诱导。我们报告了TodK的鉴定，它是双组分调节系统中一个假定的组氨酸蛋白激酶，对聚集和孢子形成的正确时间很重要。TodK功能的丧失导致早期聚集以及早期孢子形成且孢子形成水平增加。todK的转录在饥饿响应中独立于严谨反应而下降10倍。TodK功能的丧失特别导致C信号依赖性基因的一个子集的表达增加。todK突变体中加速的发育取决于C信号转导途径中的已知组分。TodK对C信号的合成不重要。从这些结果我们推测，TodK是一个信号转导系统的一部分，该系统汇聚到C信号转导途径上以负向调节聚集、孢子形成以及C信号依赖性基因的一个子集的表达。TodK和SdeK组氨酸蛋白激酶（它是一个信号转导系统的一部分，该系统汇聚到C信号转导途径上以刺激聚集、孢子形成和C信号依赖性基因表达）在独立的遗传途径中起作用。我们推测由TodK和SdeK定义的信号转导途径与C信号转导途径协同作用以控制聚集和孢子形成的时间。
