Research Abstracts Online
January 2009 - March 2010
College of Liberal Arts
Department of Biology
PI: Betsy Martinez-Vaz
Sequence Analysis of Nodulation Regulators in Sinorhizobium Strains From Different Geological Regions
Sinorhizobium meliloti (formerly Rhizobium meliloti) is a soil bacterium that forms nitrogen-fixing nodules on the roots of certain genera of leguminous plants, including Medicago, Melilotus, and Trigonella. Nodulation requires the coordinated expression of several bacterial and host nodulation genes, beginning with molecular recognition between both symbiotic partners. Flavonoid molecules, exuded by legumes, induce expression of bacterial nod genes leading to the synthesis of rhizobial oligosaccharide signal molecules called Nod factors. These bacterial signal molecules are recognized in a strain-specific manner by a receptor kinase that initiates developmental programs in the legume host resulting in the formation of a nodule.
Previous studies have shown that variations in the genotype of Sinorhizobium strains, specifically in the genes involved in nodulation, influence the ability of these organisms to have successful symbiosis with their partner legumes. The aim of this project is to use DNA sequence variations (polymorphisms) in genes encoding proteins that regulate nodulation as a tool to differentiate and classify strains of Sinorhizobum into sequence type groups. Sequence type groups were originally established by VanBerkum and colleagues, but their classification strategy did not include many genes involved in the regulation of nodulation. This project will allow the researchers to gain insights into the conservation and evolution of transcriptional regulators in Sinorhizobium strains. In addition, the project will provide information on whether DNA sequence variations on the genes encoding nodulation regulators can be used as tool for strain classification.
William Fischer, Undergraduate Student
Elizabeth Steinert, Undergraduate Student