Mapping legume directs us to health?

Scientists will soon huddle together to unravel the third plant genome to be sequenced to date. Their work - boosted recently by a $10.8 million (€9.2m) slice of funding - should shed light on the health-promoting properties buried in the legume.

The multi-institution initiative​ will see researchers, led by professor Nevin Young at the University of Minnesota in the US, sequencing the genome of the model legume, Medicago truncatula​. Medicago truncatula​ is the third plant genome to be sequenced - only Arabidopsis​, a plant widely studied as a model green plant, and rice have so far been sequenced.

According to the scientists, Medicago​ was given a high priority because it provides a strong 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'.

Legumes acquire their high protein content because of their ability to produce their own fertiliser through a process known as nitrogen fixation. Scientists believe that legumes also produce 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.

Prior to commercial fertiliser production, agriculture worldwide depended on legumes to supply the nitrogen needed to make protein, he added. Legumes perform this feat with the help of bacteria that infect their roots and form specialised 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. Young believes that 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.

"We need to have a complete inventory of the genes and gene products,"​ said Young. "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."​

The way in which legumes and the bacteria that infect their roots 'tell' each other who they are holds special interest for the researchers. This communication is essential for the two organisms to recognise each other and take the next steps in the co-operation that leads to nitrogen being 'fixed' into usable forms, explain the scientists.

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.

For Young, 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.

Funded by the National Science Foundation (NSF) the Minnesota-led project 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.

"As a model legume, the​ Medicago,/i> genome sequence is expected to revolutionise the field of plant genomics," hailed the US scientists this week.

Their research is matched by a parallel Medicago​ sequencing initiative under way in Europe, primarily in England and France. Medicago​ has eight chromosomes - of which the US group will sequence six, and the European group two. The researchers will concentrate on the gene-rich regions of chromosomes.