How Does the Plant Say-No More?: A Molecular Genetic Approach to Nodule Number Regulation

固氮菌在豆科植物根部的定殖受共生伙伴之间一系列复杂的相互作用的调节。端点是一个被称为根瘤的专门器官，它是由植物根部形成的，用来容纳细菌。作为植物提供的碳的交换，细菌从空气中为植物提供氮，使豆科植物具有在缺乏土壤氮的情况下生长的独特能力。本研究以遗传改造的模式植物蒺藜苜蓿为植物宿主，中华根瘤菌为细菌共生体，研究植物对共生关系的控制。将研究植物调节其形成的根瘤数量的机制。PI表明，根瘤数量的调节是通过根和芽之间传播的信号来实现的。 关于根和芽如何相互传递信号的四个问题仍然没有答案：什么是向芽传递的信号？是什么在拍摄中感知到信号？对根的信号的性质是什么？什么在根中接收信号？将采用生理学、遗传学和生物化学方法的组合来识别信号并确定它们是如何被感知的。为此，研究人员将分析参与调节对信号反应的基因、营养素和植物激素。 目前已知的以及新的基因和蛋白质，在这一途径中发挥作用的特点是氮肥是昂贵的生产和过量的化肥施用是地下水污染的来源，使豆类的独特能力，在土壤氮的情况下生长非常可取的农业。 由于结核数量调节途径也参与根的生长，因此该项目的结果对于未来操纵农业结瘤以及揭示所有植物如何协调茎和根的生长至关重要。 该项目将培训两名博士生和四名本科生，同时为几名高中生提供暑期研究机会。 首席研究员将通过既定的大学课程教授研究伦理方面的最佳实践，并在面向公众的科学会议和大学课程中传播该项目的成果，从而参与外联活动。

The colonization of roots of plants in the legume family by nitrogen-fixing bacteria is regulated by a complex series of interactions between the symbiotic partners. The endpoint is a specialized organ called a nodule, which is formed by the plant roots to house the bacteria. In exchange for carbon provided by the plant, the bacteria provide the plant with nitrogen from the air, allowing legumes the unique ability to grow in the absence of soil nitrogen. This project focuses on the plant's control of the symbiosis, with the genetically enabled model species Medicago truncatula as the plant host and Sinorhizobia as the bacterial symbiont. The mechanisms by which the plant regulates the number of nodules it forms will be studied. The PI has shown that regulation of nodule number occurs by way of signals that travel between roots and shoots. Four questions about how the root and shoot signal to each other remain unanswered: What is the nodulation signal to the shoot? What perceives the signal in the shoot?What is the nature of the signal to the root? What receives the signal in the root? A combination of physiological, genetic and biochemical approaches will be employed to identify the signals and determine how they are perceived. Towards this end investigators will analyze the genes, nutrients and plant hormones involved in regulating responses to the signals. Currently-known as well as new genes and proteins that function in this pathway will be characterized Nitrogen fertilizer is costly to produce and excessive fertilizer application is a source of groundwater pollution, making the unique ability of legumes to grow in the absence of soil nitrogen highly desirable for agriculture. Because the nodule number regulatory pathway is also involved in root growth, the results of this project are critical to future manipulation of nodulation in agriculture and for revealing how all plants coordinate shoot and root growth. The project will train two doctoral students and four undergraduates, while providing summer research opportunities to several high school students. The lead investigator will engage in outreach by teaching best practices in research ethics through established university programs and disseminating the results of this project at scientific meetings and university programs targeted to the general public.