PhD Student University of Florida Gainesville, Florida
Body of Abstract: Chemical nitrogen fertilizer production uses around 5% of the global natural gas produced each year. Some plants, like the model legume Medicago truncatula, benefit from a symbiotic relationship with nitrogen-fixing bacteria known as rhizobia. In this relationship, the plant recognizes the presence of rhizobia and develops a modified root structure, a root nodule, to house the bacteria. The genetic basis of root nodule symbiosis (RNS) has been extensively studied for over a century, but identifying the genes that regulate the development of this modified root organ has remained elusive. A deeper understanding of the transcriptional program underpinning the establishment of this symbiotic relationship could uncover the elements necessary to engineer RNS into non-nodulating plant species. Engineering nodulation into agricultural crops and bioenergy feedstocks could reduce nitrogen fertilizer application, in turn preventing water pollution and decreasing dependency on fossil fuels. To investigate the initial transcriptomic changes regulating root nodule symbiosis, we collected root samples of wildtype M. truncatula at 0, 24, 48, and 96 hours after inoculation with Sinorhizobium meliloti. Using 10X Genomics Single Cell RNAseq protocols on each set of samples, we produced transcriptomic profiles of individual cell types that reveal the trajectory of cell lineages, as they differentiate to form the various components of the nodule. The single-cell RNA sequencing data is now being explored to identify specific regulators that control the developmental transitions between different cell types in a lineage. Through the use of RNAi knockdown and retrotransposon insertion techniques, we are phenotypically validating potential genetic regulators chosen from the scRNAseq dataset.