The University of Minnesota has received $10.8 million from the National Science Foundation (NSF) for a multi-institution initiative to sequence the genome of a model legume known by its scientific name, Medicago truncatula (the barrel medic). Medicago truncatula is the third plant genome to be sequenced; only Arabidopsis--a plant widely studied as a model green plant--and rice have been sequenced to date. Medicago was given such high priority because it provides an excellent experimental system to study agriculturally important legumes like soybeans, mung beans, chickpeas, cowpeas, and lentils, crops that constitute the major source of protein for people throughout the developing world. Alfalfa is also a legume and is a major source of protein for foraging cattle and a close relative of Medicago truncatula.

Nevin Young, a professor with a joint appointment in the departments of plant pathology and plant biology in the university's College of Agricultural, Food and Environmental Sciences, will lead the work, which is part of NSF's plant genome research program.

Legumes acquire their high protein content by virtue of their ability to produce their own fertilizer through a process known as nitrogen fixation. Legumes also produce many novel compounds with health-promoting properties, such as anti-cancer activity.

"Legumes are responsible for a majority of the biologically generated nitrogen in the world, especially in agriculture," said Young. That is, before the expensive, energy-intensive process of commercial fertilizer production was invented, agriculture worldwide depended on legumes to supply the nitrogen needed to make protein. Legumes perform this feat with the help of bacteria that infect their roots and form specialized structures called nodules. Within nodules, nitrogen gas from the air is converted into a form that living organisms can use to make amino acids and proteins.

The special compounds legumes make include phytoestrogens and isoflavones, which have been linked to many health benefits. By sequencing the genome, scientists will have the basic tool to understand all these processes and put them to work to improve health and nutrition, Young said.

"We need to have a complete inventory of the genes and gene products," he said. "Until then, we won't even know what we don't know about legume biology. It's like trying to build a car without a complete parts list. With the genome sequence, scientists can sit down and look at all the pieces involved in making health-promoting compounds, converting nitrogen to a usable form, and packing legumes with protein and figure out ways to make them work better."

Of special interest is the way legumes and the bacteria that infect their roots "tell" each other who they are. Such communication is essential for the two organisms to recognize each other and take the next steps in the cooperation that leads to nitrogen being "fixed" into usable forms. The only way to understand the communication is to get a complete gene sequence for legumes, said Young. The sequence for the infecting bacteria has already been determined, in a project that included another University of Minnesota professor, Michael Sadowsky.

The value of having the Medicago gene sequence will be manifold.

"We want to develop more intelligent ways of using crops through traditional breeding, as well as new avenues for applying biotechnology," said Young. "We want plants to fix nitrogen and produce useful compounds as efficiently as possible." He noted that the genes governing the interactions between legumes and beneficial bacteria also control interactions with soil fungi. The roots of many crops, trees and other plants depend on the biochemical "talents" of fungi in order to extract water and nutrients from soil.

Young directs a group that includes Bruce Roe, director of the University of Oklahoma Genome Center, and Chris Town of The Institute for Genome Research (TIGR) in Rockville, Md. The cooperative agreement between Minnesota and NSF is for $10.8 million over three years, and it adds to more than $5 million in Medicago genomics research already underway at Minnesota. Young will direct the sequencing project and coordinate its bioinformatics component in cooperation with Ernest Retzel of Minnesota’s Center for Computational Genomics and Bioinformatics. Bioinformatics is the discipline that deals with extracting useful information from reams of data, such as is generated in any sequencing project. Roe and Town will lead the actual DNA sequencing work, which will be performed at highly specialized robotic facilities at Oklahoma and TIGR.

The Minnesota-led project is matched by a parallel Medicago sequencing initiative under way in Europe, primarily in England and France. Medicago has eight chromosomes; the U.S. group will be sequencing six, and the European group will sequence two. The researchers will concentrate on the gene-rich regions of chromosomes.

As a model legume, the Medicago genome sequence is expected to revolutionize the field of plant genomics. Scientists will quickly begin to discover the genes responsible for important biological processes like nitrogen fixation, plant-microbe symbiosis and the synthesis of health-promoting compounds. The Medicago sequence is also expected to speed the development of new scientific tools for legume research, including DNA chips and DNA microarrays, techniques that enable researchers to predict the functions of proteins. The Medicago genome sequence is even expected to simplify and accelerate future sequencing efforts envisioned for crops like soybean.