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.
