Development of Genetic Resources to Dissect Gene Regulatory Networks Governing Nodule Development and Differentiation in Medicago Truncatula

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PI: Michael Udvardi (Samuel Roberts Noble Foundation, Inc.)CoPIs: Rujin Chen and Kirankumar Mysore (Samuel Roberts Noble Foundation, Inc.)Legumes are second only to grasses in importance to humans for agriculture. Legumes have been an integral part of agricultural systems for thousands of years, and remain important for sustainable agriculture today because they can establish symbioses with nitrogen-fixing bacteria called rhizobia that supply their host plant with reduced nitrogen. This means that legumes can grow in soils containing little or no mineral or organic nitrogen, without the need to add economically and environmentally-expensive industrial nitrogen fertilizers. Symbiotic nitrogen fixation in legumes takes place in specialized organs that develop from root cells following contact with rhizobia in the soil. Rhizobia colonize plant cells in the developing nodules before differentiating into a nitrogen-fixing form called the bacteroid. Development and differentiation of legume nodules and bacteroids involve coordinated changes in the expression of thousands of plant and bacterial genes. While tremendous advances have been made recently in our understanding of plant-microbe signaling during the early stages of the legume-rhizobia interaction, little is known about how the plant regulates the massive changes in gene expression that underpin nodule development and differentiation. This project aims to use cutting-edge gene expression-profiling technology and to develop Tnt1-insertion and Fast Neutron Bombardment (FNB)-deletion mutant populations to identify regulatory genes that re-program plant cells during nodule development and differentiation. The project will focus, in particular, on transcription factor and miRNA genes, two classes of genes that are known to play leading roles in transcriptional and post-transcriptional regulation of gene expression in plants. Microarray data generated in the course of this project will be available through a project web site, GEO, and the Legume Information Service (LIS; www.comparative-legumes.org). Flanking sequence data and biological resources can be accessed via the project web site, LIS, the Medicago Genome Project website (www.medicago.org/genome), or by directly contacting project senior personnel and/or the curator of Biological Resources, Dr. Jiangqi Wen (jwen@noble.org). The research is trans-disciplinary in nature and requires the application of genomics, functional genomics, and bioinformatics with the more classical disciplines of genetics, molecular and cell biology, and plant physiology. By providing a single training ground at the Noble Foundation, this project will empower postdoctoral fellows, students, and technical staff to learn many of the research skills that are essential for cutting-edge biological research. This project will also participate in the Noble Foundation's strong student outreach program to maximize teaching and learning outcomes. Finally, the project will take advantage of existing domestic and international collaborations to strengthen links between scientists in the USA, Europe, and Australia.