Scientists from the J. Craig Venter Institute (JCVI), along with a team of international researchers led by those at the University of Minnesota, have sequenced and published a draft genome of the model legume, Medicago truncatula, also known by its common name, "barrel medic." The results of this multi-year project were published this week in the online edition of the journal Nature.
JCVI researchers, led by Christopher Town, Ph.D., played a major role in the genome sequencing, analysis and annotation. The team used a combination of traditional and next generation sequencing and assembly methods to reconstruct 375 million base pairs of the approximately 500 Mb genome, capturing nearly 94% of the Medicago genes.
Legumes (such as peas, soybeans, and alfalfa) are unique because they have a root structure called a nodule that allows for nitrogen fixation through a symbiotic process with bacteria. In this study researchers proved that nearly 58 million years ago Medicago evolved through a whole genome duplication process. Ancient genes split into pairs that separately control complementary forms of symbiosis (nodulation and mycorrhization), enabling fixation of atmospheric nitrogen into organic forms that can be utilized by the plant. This is known as "genetic sub-functionalization" and is considered an important scientific theory about how novel genes evolve in both plants and animals.
Better understanding of Medicago could lead to improvements in other cultivated legumes such as alfalfa. The increased knowledge about the evolution of legumes and their nitrogen fixing qualities might also lead to improved methods for crop fertilization.
"This has been a great team effort, both by past and present members of the sequencing and informatics groups at JCVI and by so many collaborators both in the United States and abroad," said Dr. Town. "We are looking forward to discovering more of Medicago's secrets in the coming years."
Funding for sequencing the Medicago truncatula genome was provided by the National Science Foundation and the Noble Foundation. The project was coordinated at the University of Minnesota, and involved many partner institutions (in addition to JCVI), including: the University of Oklahoma; Genoscope; the Wellcome Trust Sanger Institute; CNRS/INRA-Toulouse; John Innes Centre; Noble Foundation; University of Wageningen; MIPS-Munich; Ghent University; and the National Center for Genome Resources (NCGR). The Nature paper includes 128 co-authors at 31 institutions in 8 countries.