TRANSDUCTION OF THE A SIGNAL IN MYXOCOCCUS DEVELOPMENT

黄色粘球菌利用细胞间的相互作用来协调 细胞聚集形成有组织的发育程序 多细胞子实体与杆状细胞的分化 变成卵形孢子。这一发展计划是由营养素发起的 在高细胞密度下的限制。去除营养物质后，M。 黄花细胞通过以下方式感知其营养状态和细胞密度 监测胞外A信号浓度的增加，以及 随后激活A信号转导通路。激活 仅当细胞外A信号浓度在 特定的中间范围。使用敏感的传感机制， 一条信号通路引导着M的早期进展。 黄花发展。 我们的长期目标是确定：1)细胞如何感知 细胞外A信号浓度，2)该信息是如何 转导，导致基因表达的变化以及3)什么是 基因表达变化与复合体之间的联系 多细胞子实体形成的行为反应。回答 这些问题我们将描述A监管网络的特征 信号转导途径。该电路的几个组件具有 包括胞外信号、A信号和A信号 特异性反应，一个基因的表达增加，gen4521。一个 已确定与SAASA对应的监管要素(用于 信号的抑制者)轨迹。需要使用saa轨迹。 通过早期发育的进展，并差别化地调节 不同的A信号依赖基因的表达。 本研究的重点是利用经典遗传学和分子遗传学 技术，结合蛋白质生物化学，以充分表征 SASA基因座及其编码的调控元件。分子遗传学 将使用各种方法来分析SAASA轨迹结构，方法如下： 基因的物理限制，分析转录本，测序 区域，确定开放阅读框架(S)，并构建和 以零突变为特征。研究SASA基因的功能 产品我们将直接确定SASA基因产物还是 间接调节基因4521的表达。第一，顺势而为 将确定控制基因4521表达的调控元件 通过缺失分析。然后，将使用生化技术来检测 纯化的sasa基因产物与基因4521调控区的结合。 任何结合活动都将详细描述。如果SASA基因 产品似乎间接调节了基因4521的表达，生化 技术以及基因筛查将被用来识别可能的 中间监管要素。此外，基因筛查将是 开发用于识别A信号转导的其他组件 途径，这可能包括一个受体和额外的 转导元件。

Myxococcus xanthus uses cell-cell interactions to coordinate a developmental program in which cells aggregate to form organized multicellular fruiting bodies and differentiate from rod-shaped cells into ovoid spores. This developmental program is initiated by nutrient limitation at a high cell density. After the removal of nutrients, M. xanthus cells sense their nutritional status and cell density by monitoring the increase in the extracellular A signal concentration, and subsequently activate the A signal transduction pathway. Activation occurs only when the extracellular A signal concentration is within a specific intermediate range. Using a sensitive sensing mechanism, the A signal pathway directs the progression through the early stages of M. xanthus development. Our long term goals are to determine: 1) how the cells sense the extracellular A signal concentration, 2) how this information is transduced, resulting in a change in gene expression and 3) what is the connection between the change in gene expression and the complex behavioral response of multicellular fruiting body formation. To answer these questions we will characterize the regulatory network of the A signal transduction pathway. Several components of this circuitry have been identified, including the extracellular signal, A signal, and a specific response, an increase in expression of a gene, gene4521. A regulatory element has been identified which maps to the sasA (for suppressor of A signal) locus. The sasA locus is required for the progression through early development and differentially regulates the expression of distinct A signal-dependent genes. The focus of this research is to use classical and molecular genetic techniques, combined with protein biochemistry, to fully characterize the sasA locus and its encoded regulatory element. Molecular genetic approaches will be used to analyze the sasA locus structure by defining the physical limits of the locus, analyzing the transcripts, sequencing the region, identifying the open reading frame(s), and construction and characterizing a null mutation. To study the function of the sasA gene product we will determine if the sasA gene product directly or indirectly regulates gene4521 expression. First, the cis-acting regulatory elements controlling gene4521 expression will be determined by deletion analysis. Then, biochemical techniques will be used to test binding of purified sasA gene product to the gene4521 regulatory region. Any binding activity will be characterized in detail. If the sasA gene product appears to indirectly regulate gene4521 expression, biochemical techniques as well as genetic screens will be used to identify possible intermediate regulatory elements. In addition, genetic screens will be developed to identify other components of the A signal transduction pathway, which will likely include a receptor and additional transduction elements.