Cereals such as rice (Oryza sativa) are staple food for human and animal nutrition. Because cereal growth is limited by nitrogen, the high yields of these crops are currently dependent on fertilizers that are a major on-farm expense and cause significant environmental damages. In view of the increasing demand for higher production of these crops, the development of alternative strategies to enhance crop production while reducing fertilizer use is of high priority. One such strategy is to use rhizobia that form intimate endophytic association with these crops and increase their growth. Rhizobia are soil bacteria that form a very efficient nitrogen-fixing association with legumes. Recent studies have shown that rhizobia hijacked the genetic machinery of legumes involved in symbiosis with mycorrhizal fungi. Similar to legumes, rice forms symbiosis with mycorrhizal fungi and contain the homologues of legume genes necessary for interactions with rhizobia. Preliminary results from the investigators' laboratories indicate that a rhizobial strain utilizes the mycorrhizal symbiotic pathway to colonize rice tissues. The goal of this project is to determine the molecular and cellular mechanisms of both rhizobia and rice that result in this beneficial association as well as to evaluate the potential of rhizobial nitrogen fixation with rice. This rhizobial-cereal interaction provides a unique opportunity to study the initial relationships and mutual benefits that probably allowed legume nodulation to appear but also, in the long term, to use this system to engineer nitrogen fixation in cereals by following the path of legume evolution.
The broader impacts of this project for the education and professional development include the interdisciplinary training for students and postdoctoral fellow that include experience in microbial and plant genetics, molecular biology, microscopy and plant-microbe interactions. Numerous outreach and educational opportunities will be provided for undergraduate, graduate and postdoctoral students. The benefits of microbial symbioses will also be emphasized in directed research programs targeting minority undergraduate and K-12 students in both laboratories as well as using the public outreach programs in both campuses of the University of Wisconsin.
