The impact of nutritional signaling on transmission of endosymbiotic Wolbachia bacteria

内共生是指一种生物寄居在另一种生物体内。其中最成功的内共生体之一是沃尔巴克氏杆菌，这种细菌在大约一半的昆虫物种中携带，包括模式昆虫果蝇和果蝇。像许多其他内共生体一样，沃尔巴克氏菌在卵子发育过程中由雌性传播给后代。该项目的总体目标是阐明促进沃尔巴克氏杆菌母体传播的细胞和分子机制。这将包括建立一个沃尔巴克氏菌对果蝇卵细胞定植的数学模型，并使用该模型来测试对发育中的卵中沃尔巴克氏菌密度的影响因素的预测。模拟细胞内共生菌的动力学几乎是史无前例的，因此这项工作将提供新的见解以及一个有价值的分析工具。此外，还将阐明调节寄主运输的营养信号，从而阐明果蝇卵内沃尔巴克氏菌的分布。由于细胞运输过程对于建立昆虫身体计划也是至关重要的，这些分析将使沃尔巴克氏菌的传播和昆虫发育成为一个综合过程。这将把被视为机械分离的概念联系在一起。这项研究将在一个少数族裔占多数、服务于拉美裔美国人的机构进行，也是美国最大的STEM少数族裔本科学位的生产商。执行这一项目的受训者还将撰写解释研究实践和益处的论文。这些论文将在一个基于网络的外展论坛上分享，以丰富公众对科学的理解。这种由母体传播的细菌具有精简的基因组和兼性的细胞内生活方式。沃尔巴克氏菌在昆虫种群中的高流行率要求采取强有力的传播增强战略。这个项目的总体目标是应用化学、遗传和营养方法来确定寄主饮食和营养响应信号对沃尔巴克氏菌和卵子发生中生殖系决定因素定位的影响。第一个目标是确定沃尔巴克氏菌如何将果蝇母系生殖细胞作为一个完整的生理过程进行定植。虽然发育中的卵母细胞中的沃尔巴克氏菌滴度对宿主的操纵有反应，但宿主和共生体对滴度调节的相对贡献尚不清楚。为了解决这个问题，将对沃尔巴克氏菌的生活史和入侵动态以及宿主生殖系的发育率进行细胞学评估，并用于估计数学模型的参数。该模型将第一次测试沃尔巴克氏菌在宿主-菌株组合中的定植机制的保护，以及对营养敏感信号提示的反应。第二个目的是阐明战略沃尔巴克氏菌定位是如何在卵子发生过程中被调控的。在黑腹毛虫中，基于微管的运动蛋白在卵母细胞后皮质集中沃尔巴克氏菌和后部/生殖系决定因素，从而将沃尔巴克氏菌预先定位在生殖细胞形成地点。营养信号对这一过程的影响将使用遗传方法进行研究。综上所述，这项工作将全面了解这种内共生菌传播的细胞基础。

Endosymbiosis involves one organism dwelling inside another. One of the most successful endosymbionts is Wolbachia pipientis, a bacterium carried by about half of insect species, including the model insect Drosophila, the fruit fly. Like many other endosymbionts, Wolbachia are transmitted by females to their offspring during egg development. The overall goal of this project is to elucidate the cellular and molecular mechanisms that facilitate Wolbachia maternal transmission. This will include creating a mathematical model of fruit fly egg-cell colonization by Wolbachia, and using the model to test predictions about the factors governing Wolbachia density within developing eggs. Modeling intracellular endosymbiont dynamics is virtually unprecedented, thus this work will provide new insights as well as a valuable analytical tool. In addition, the nutritional signals that regulate host transport and thus Wolbachia distribution within fruit fly eggs will be elucidated. As cellular transport processes are also crucial for establishing the insect body plan, these analyses will inform Wolbachia transmission and insect development as an integrated process. This will link concepts that have been regarded as mechanistically separate. The research will be performed at a majority-minority, Hispanic-serving institution and the nation's largest producer of STEM minority undergraduate degrees. Trainees carrying out this project will also create essays that explain research practices and benefits. These essays will be shared in a web-based outreach forum to enrich public understanding of science.Wolbachia pipientis is among the most widespread of endosymbionts. This maternally transmitted bacterium has a streamlined genome and a facultative intracellular lifestyle. The high prevalence of Wolbachia in insect populations requires robust transmission-enhancing strategies. The overall goal of this project is to apply chemical, genetic and nutritional approaches to define the impacts of host diet and nutrient-responsive signaling on Wolbachia and germline determinant localization in oogenesis. The first aim involves defining how Wolbachia colonize Drosophila maternal germline cells as an integrated physiological process. Though Wolbachia titer in developing oocytes is responsive to host manipulation, the relative contributions of host and symbiont to titer regulation is unknown. To address this issue, Wolbachia life cycle and invasion dynamics, as well as host germline development rates will be assessed cytologically and used to estimate the parameters of a mathematical model. The model will be the first to test for conservation of Wolbachia colonization mechanisms across host-strain combinations, as well as in response to nutrient-sensitive signaling cues. The second aim is to elucidate how strategic Wolbachia localization is regulated during oogenesis. In D. melanogaster, microtubule-based motor proteins concentrate Wolbachia and posterior/germline determinants at the oocyte posterior cortex, thus pre-positioning Wolbachia at the germ cell formation site. The impact of nutritional signaling on this process will be studied using genetic approaches. Taken together, this work will comprehensively inform the cellular basis for transmission of this endosymbiont.