A Novel Myosin Required for Dictyostelium Development

感知和响应环境中营养水平的能力对生物体的生存至关重要。单细胞采用的一种策略是盘基骨菌，它通过启动一个简单而优雅的发育程序来形成孢子，从而在食物短缺的情况下存活下来。盘基ostelium是如何检测到食物已经变得有限，然后启动它们的发育程序的？现有的数据表明，它们感知到一种未表征的分泌因子水平的变化，这种因子使它们能够监测盘基钢柱细胞与它们的食物来源——细菌的比例。如果不能分泌这个因子，就会导致缺乏对食物的反应，细胞就不能发育出孢子。一种盘基钢索菌突变体由于不能分泌监测食物水平所需的关键因子而无法启动发育周期。这个突变体是一个有用的工具，将被用来确定触发盘基骨门发育开始的因素。将追求两个目标：(1)将使用生化方法来分离和充分表征该因子；(2)确定突变表型的分子基础。突变基因编码一种新型肌凝蛋白。这种运动蛋白在一个关键发育因子分泌中的作用将被研究。该项目的成功完成将为盘基骨柱如何利用一种分泌因子来启动发育以及一种独特的肌凝蛋白在这一过程中的作用提供重要的信息。这种触发机制的识别应该作为一个范例，说明分泌因子如何用于监测生物体的环境以及启动关键的发育过程。该项目将为博士后、研究生和本科生提供研究培训。

The ability to sense and respond to nutrient levels in the environment is essential for the survival of organisms. One strategy employed by single cells is exemplified by Dictyostelium, which survives a food shortage by initiating a simple, yet elegant, developmental program resulting in the formation of spores. How do Dictyostelium detect that food has become limiting and then initiate their developmental program? The available data indicate that they sense changes in the levels of an uncharacterized secreted factor(s) that allow them to monitor the ratio of Dictyostelium cells to their food source, bacteria. Failure to secret this factor(s) results in a lack of response to a loss of food, and the cells do not develop spores. A Dictyostelium mutant that fails to initiate the developmental cycle because it does not secrete the critical factor(s) required for monitoring food levels has been identified. This mutant is a useful tool that will be exploited to identify the factor(s) that triggers the onset of development in Dictyostelium. Two aims will be pursued: (1) A biochemical approach will be used to isolate and fully characterize the factor; (2) The molecular basis for the mutant phenotype will be determined. The mutant gene encodes a novel type of myosin. The role of this motor protein in the secretion of a critical developmental factor will be investigated. The successful completion of this project should provide fundamentally important information about how Dictyostelium employs a secreted factor(s) to initiate development and the role of a unique myosin in the process. Identification of this triggering mechanism should then serve as a paradigm for how secreted factors are used to monitor an organism's environment as well as initiate key developmental processes. This project will provide research training for post-doctoral associates, graduate students, and undergraduates.