CAREER: Exploring the Transcriptional Regulatory Networks Controlling the Early Stages of Legume Nodulation

一组被称为根瘤菌的细菌将大气中的氮转化为一种化学形式，可用于支持豆科植物的生长和繁殖。这些细菌与它们的豆类宿主建立了共生关系，居住在根瘤中，在根瘤中发育专门的结构，以促进两个伙伴之间的营养交换。这是一个重要的经济过程，因为它减少了种植作物所需的氮肥数量，是可持续农业的关键组成部分。因此，更好地了解控制结瘤过程的分子机制应该有助于深入了解更有效地捕获和固定大气氮的方法，并将这种能力转移到非豆科植物。在我们对豆科植物结瘤的理解中，一个显著的成就是描述了控制根瘤菌感染植物根毛细胞的信号步骤，根瘤菌是结瘤的初始步骤。这一共生途径受豆科植物根毛细胞中近2000个基因的调控。研究人员将描述一个在控制结瘤早期阶段至关重要的基因网络。除了对豆科植物研究的影响外，这个项目的更广泛的影响包括为俄克拉荷马州来自代表性不足群体的高中生和本科生开发独特的教育计划，促进研究和教育的紧密结合。这个职业项目建立在一个假设的基础上，即在共生途径的一个或多个转录因子的直接控制下的调控网络协调根毛细胞中基因表达的适当激活和时机，以响应根瘤菌。该项目特别关注结瘤信号通路1(NSP1)调控网络，将解决两个关键问题：NSP1直接控制的大豆和紫花苜蓿根毛基因的同一性是什么？与NSP1相关的蛋白质复合体是什么，它们如何控制根瘤菌接种后根毛基因的表达？为了回答这些问题，研究人员将1)通过高通量测序技术并应用DamID-SEQ或CHIP-SEQ方法，鉴定直接在转录因子GmNSP1a和b控制下的大豆根瘤菌响应大豆根瘤菌的根毛基因；2)通过免疫共沉淀鉴定GmNSP1a和b在接种大豆根瘤菌后根毛细胞中的蛋白质对；3)验证大豆和模式豆科植物紫花苜蓿之间根毛基因调控网络的保守性。

A group of bacteria called rhizobia convert atmospheric nitrogen to a chemical form available to support growth and reproduction of plants in the legume family. The bacteria establish a symbiotic relationship with their legume hosts, residing in root nodules where specialized structures develop to facilitate the exchange of nutrients between the two partners. This is an economically important process as it reduces the amount of nitrogen fertilizer needed to grow crops and is a key component in sustainable agriculture. Thus, a better understanding of the molecular mechanisms controlling the nodulation process should lead to insights about more effective ways to capture and fix atmospheric nitrogen and to the transfer of this capacity to non-legume plants. One notable achievement in our understanding of legume nodulation is the characterization of the signaling steps that control the infection of the plant root hair cell by rhizobia, the initial step of nodulation. This symbiotic pathway is regulated by almost 2000 genes in legume root hair cells. The investigators will characterize a network of genes essential in controlling the early stages of nodulation. In addition to its impact on legume research, the broader impacts of this project include the development of unique educational programs dedicated to Oklahoma high-school and undergraduate students from under-represented groups, promoting strong integration between research and education.This CAREER project is built on the hypothesis that regulatory networks directly under the control of one or several transcription factors of the symbiotic pathway orchestrate the proper activation and timing of gene expression in root hair cells in response to rhizobia. Specifically focusing on the Nodulation Signaling Pathway1 (NSP1) regulatory network, this project will address two key questions: What is the identity of the soybean and medicago root hair genes directly under the control of NSP1? What are the protein complexes asscociated with NSP1 and how do they control the expression of root hair genes in response to rhizobial inoculation? To answer these questions, the investigators will 1) characterize the soybean root hair genes directly under the control of the transcription factors GmNSP1a and b in response to Bradyrhizobium japonicum through high-throughput sequencing technologies and by applying DamID-seq or ChIP-seq methods, 2) identify the protein partners of the GmNSP1a and b in root hair cells inoculated with B. japonicum by co-immunoprecipitation of the protein partners in root hair cells upon rhizobia inoculation; 3) validate the conservation of the root hair gene regulatory networks between soybean and Medicago truncatula, the model legume.