Project Participants

J. Stephen Gantt, PI, University of Minnesota
Maria J. Harrison, co-PI, Boyce Thompson Institute/Cornell University
Ernest Retzel, co-PI, University of Minnesota
Carroll Vance, co-PI, University of Minnesota/USDA ARS
Kathryn A VandenBosch, co-PI, University of Minnesota
Deborah Samac, key-collaborator, University of Minnesota/USDA ARS

Objectives and Approaches

The legume Medicago truncatula forms symbiotic associations with rhizobial bacteria, leading to nodule development and nitrogen fixation, and arbuscular mycorrhizal fungi, resulting in enhanced phosphorous nutrition. These associations do not occur in the model plant Arabidopsis thaliana.

With prior support from the NSF Plant Genome Program, members of this research team have participated in the generation and large-scale analysis of M. truncatula's expressed sequences, with a particular focus on symbiosis. While cDNAs for most of the genes expressed during rhizobial and mycorrhizal symbioses were cloned in these studies, their function is largely unknown. The overall objectives of this project are to identify genes that are essential for symbiotic development and to provide insights into their roles. Building on resources developed in the previous EST project, the research team will use RNA interference (RNAi), to systematically silence the expression of 1,500 genes implicated in the development or functioning of the rhizobia-legume or mycorrhizal symbioses. Transgenic roots will be tested for altered symbiotic interactions and genes essential for development of these symbioses will be identified. Descriptions of the resulting root and symbiotic phenotypes will be disseminated to the scientific community electronically and a resource of 1,500 RNAi-inducing plasmids will be made available.

Broader Impacts

The legume family is the third largest family of flowering plants and one of the most agriculturally and ecologically significant. Via their interactions with rhizobia and mycorrhizal fungi, legumes participate in the cycling of nitrogen and phosphorus, the two major mineral nutrients most frequently limiting for plant growth. Their ability to form both symbioses and their importance as a protein source in many human and animal diets, makes legumes of central importance to sustainable agriculture. The research proposed, employs one of the latest and most powerful genomic technologies, RNA interference, to identify and ascribe functions to genes required for symbiosis. The research team will integrate selected undergraduate students into all aspects of the research providing them with exposure to the use of genomics technologies to answer fundamental questions about plant-microbe symbioses. Additionally, the investigators will work with faculty at Gustavus Adolphus College, an undergraduate institution, to develop a laboratory course that follows the general protocols described in this research program. The outcome of this collaborative effort will be the description of a series of experiences that undergraduate students in plant biology, plant molecular biology, or plant physiology can obtain in one semester course.