KSEF RDE: Genetic Regulation of Nodulation Specificity in Medicago Truncatula

A hallmark trait of legumes is their unique ability to establish a symbiotic relationship with nitrogen-fixing soil bacteria known as rhizobia. The mutualism culminates in the formation of a new plant organ, called the root nodule, within which the bacteria convert atmospheric nitrogen into ammonia, a biological form that can be directly consumed by the plant. One striking feature of the legume-rhizobial symbiosis is its high level of specificity. Such specificity occurs at both inter- and intra-species levels and takes place at multiple phases of the interaction, ranging from initial bacterial infection and nodulation (nodulation specificity) to late nodule development associated with nitrogen fixation (nitrogen fixation specificity). The overall goal of this proposal is to investigate novel genetic mechanisms underlying nodulation specificity in the Medicago-Sinorhizobium system. The specific objective of the project is to clone a dominant gene in Medicago truncatula that restricts nodulation by Sinorhizobium meliloti strain Rm41.