Submitted to: Legume Crop Genomics
Publication Type: Book / Chapter
Publication Acceptance Date: 3/1/2004
Publication Date: 6/1/2004
Citation: Ivashuta, S., Gantt, S., Vance, C.P. 2004. Medicago truncatula as a model legume. In: Wilson, R.F., Brummer, E.C., Stalker, H.T., editors. Legume Crop Genomics. American Oil Chemists' Society Press, Champaign, IL. p. 143-161. Interpretive Summary: Legume crops such as soybeans, peas, alfalfa, and dry beans provide about 33% of the human's dietary protein needs. They also provide 35-40% of the world's cooking oil needs. Not only are legumes important for their nutritional value, but also they contribute to making agriculture more sustainable. Their importance in sustainable cropping systems is because they can make their own nitrogen fertilizer through a process called symbiotic nitrogen fixation (SNF) and do not need chemical sources of nitrogen fertilizer. They are also good for keeping soil healthy. Genomics, the study of an organism's complete genetic makeup, has fostered striking growth in the fundamental understanding of how crops grow and develop. This field of science has been based upon the study of selected plant species as model organisms. The current model plant species are incapable of making their own nitrogen fertilizer through SNF. Therefore, legumes must be considered as models for SNF. Little information exists as to which legume plant should serve as a model for genomic studies of SNF. This report documents the rationale for selecting Medicago truncatula as a model legume and how Medicago can be used in genomic studies. The report is useful because it lays the foundation for genomic studies in legumes and it identifies new approaches to ascertain the function of plant genes.
Technical Abstract: Several attributes contribute to Mt serving as a model plant for legume genomics: a small, simply organized genome; a fairly well-developed genetic and physical map; synteny with diploid alfalfa and soybean; prolific seed production and short generation time; an excellent population of mutants; and a large number of ESTs from more than 40 libraries derived from a wide range of organs and conditions. Moreover, Mt is readily transformed with both A. tumefaciens and A. rhizogenes and is susceptible to gene silencing through RNAi thus facilitating functional genomics. These advances, coupled to transcript profiling and proteome analysis related to root symbiotic interaction with rhizobial and mycorrhizae, place Mt in a strong position to define legume functions and processes. Adding substantial strength to the Mt model is the recent commitment by NSF to fund sequencing the euchromatic gene space. Because gene sequencing, transcript profiling, proteome analysis, metabolic profiling, and mutant analysis progress at a logarithmic pace, we will be challenged to integrate information into coherent molecular models that define plant growth and development. This integration will require even more collaboration between geneticists, biochemists, and bioinformaticians than has occurred to date. Even more importantly the information will need translation to crop improvement through plant breeders. The gen-, prote-, metabol-, transcript- omics umbrella is large and interdisciplinary and will give unimaginable insight into crop plant production. However, to achieve these insights and improve human well being through food security will require exceptional communication as well as exceptional science.