Function of non-legume orthologs of legume genes required for nodulation and arbuscular mycorrhizal symbiosis

Grants and Contracts Details


In natural ecosystems, many plants are able to grow on nutrient-poor soils, and they do so by living together for mutual benefit with microorganisms, an example of a process called symbiosis. The symbiosis between arbuscular mycorrhizal (AM) fungi and >80% of land plants and that between rhizobia and legumes represent the two most important symbiotic interactions between plant roots and microbes. In the AM symbiosis, the AM fungi assist the plant in assimilating phosphate, whereas in the legume-rhizobia symbiosis, the rhizobia fix atmospheric nitrogen for use by the plant. The finding that the two symbiosis share overlapping signaling pathways in legumes suggests that the evolutionary younger nitrogen-fixing symbiosis has acquired functions from the ancient AM symbiosis. Most recently, a number of legume genes required for nodulation and AM symbiosis were cloned from several legumes. Interestingly, nearly all these genes are highly conserved across multiple plant taxa, and their putative orthologs can be defined in non-legumes such as rice and Arabidopsis. This observation provides a unique opportunity to investigate ortholog functionality across species and to address questions pertinent to the evolution of AM and nodulation symbiosis in plants. The research proposed herein seeks to elucidate the function of non-legume orthologs of legume genes required for nodulation and AM symbiosis. Specific objectives are: (I) Characterization of the function of the putative rice orthologs of legume genes required for nodulation and AM symbiosis using reverse genetics tools; (2) Complementation of the legume mutants that are defective in nodulation and/or AM symbiosis using the putative rice orthologs; and (3) Comparative transcript profiling of wild-type and mutant rice lines under the infection of AM fungi using the Rice Affymetrix GeneChip. Broader Impacts of the Proposed Research The AM and rhizobial symbioses are of critical importance in sustainable agriculture, since growth of land plants is often limited by the amounts of nitrogen and phosphate in the soil. An in-depth understanding of the genetic and molecular mechanisms underlying both symbioses will help to improve the efficiency of plants for acquisition of phosphorus and nitrogen from natural ecosystems. From an evolutionary point of view, the proposed research will provide novel insights into the evolution of gene functions and pathways leading to species- or family-specific phenotypes, and will also bridge the gap between comparative plant genomics and comparative plant biology. Education will be a major focus of this proposal. In addition to integrating the proposed research with teaching, the PI will also serve as a mentor to graduate and undergraduate students and to postdoctoral researchers who will conduct the proposed research. The students and postdocs will be trained in the areas of plant comparative and functional genomics, molecular biology of plant-microbe interactions, evolution, and bioinformatics. We will particularly encourage the participation of members of under-represented undergraduates to join our group. Undergraduates will be recruited from university organizations whose membership is specifically composed of women and minorities. Moreover, we will contribute in a direct and substantive manner to high school education in Kentucky through a high school student and teacher outreach program at the University of Kentucky.
Effective start/end date7/1/0712/31/11


  • National Science Foundation: $480,000.00


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