Joint Research on Myxobacterial Development

黏菌是独特的革兰氏阴性菌，经历多细胞发育。当营养物质在固体培养基中耗尽时，细胞聚集形成土墩，最终转化为子实体。杆状细胞分化成圆形或卵球形孢子。在黄粘球菌的发育过程中，已知发生了五个细胞间信号交换周期。fruA基因编码一种25 kda的转录因子，对黄豆的发育至关重要。在本研究中，我们通过凝胶转移实验证明了fruA表达的推定抑制因子X的存在。结合竞争实验表明是X识别序列。质谱分析了fruA突变抑制蛋白P15的结构。在ORF134中插入卡那霉素抗性DNA片段导致发育失败，这表明ORF134- frub操纵子的存在与M.xanthus发育有关。该操纵子有两个启动子结构：一个启动子在营养生长过程中起作用，而两个启动子在发育过程中都起作用。mxanthus lonD是一种热休克基因。lonD的表达不依赖于编码大肠杆菌RpoH同源基因的sigBCE基因，而依赖于编码RpoH同源基因的hsfA和sigA基因。hsfA基因编码双组分系统的一个假定效应，该效应被HsfB激酶磷酸化。与lonD基因启动子序列结合的磷酸化hsfa。M.xanthus携带至少13种真核样丝氨酸/苏氨酸激酶。双杂交实验发现许多基因产物与Pkn激酶相互作用。

Myxobacteria are unique gram-negative bacteria which undergo multicellular development. When nutrients are depleted in a solid medium, cells aggregate to form mounds which eventually convert to fruiting bodies. Rod-shaped cells differentiate to round or ovoid spores. During the development of Myxococcus xanthus, five cycles of intercellular signal exchanges are known to occur. The fruA gene encodes a putative 25-kDa transcription factor essential for the development of M.xanthus. In the present study, we have demonstrated the presence of a putative repressor X for fruA expression by gel shift experiments. Binding competition experiments suggested the X recognition sequence. Structure of protein P15, expression of which was inhibited by the fruA mutation, was analyzed by mass spectroscopy. Insertion of kanamycin-resistance DNA fragment into ORF134 resulted in failure of development, suggesting the presence of ORF134-fruB operon responsible for M.xanthus development. Two promoter structures were found for this operon : One promoter works during vegetative growth, while both two promoters work during development. M.xanthus lonD was found to be a heat shock gene. Expression of lonD was independent on sigBCE genes encoding an Escherichia coli RpoH homolog, but dependent on hsfA and sigA encoding a RpoD homolog. The hsfA gene encodes a putative effecter of a two-component system, which was phosphorylated by HsfB kinase. Phosphorylated-HsfA bound to promoter sequence for lonD gene. M.xanthus carries at least 13 eukaryotic-like protein Ser/Thr pkn kinases. Many gene products were found to interact with Pkn kinases by two-hybrid experiments.