Medicago truncatula
Encyclopedia
Medicago truncatula is a small legume native to the Mediterranean region that is used in genomic
research. It is a low-growing, clover
-like plant 10–60 cm tall with trifoliate leaves
. Each leaflet is rounded, 1–2 cm long, often with a dark spot in the center. The flower
s are yellow, produced singly or in a small inflorescence
of 2-5 together; the fruit
is a small spiny pod.
This species has been chosen as a model organism
for legume biology because it has a small diploid genome
, is self-fertile, has a rapid generation time and prolific seed production, and is amenable to genetic transformation
. The genome of M. truncatula is currently being sequenced.
It forms symbioses
with nitrogen-fixing
rhizobia
(Sinorhizobium meliloti
and Sinorhizobium medicae) and arbuscular mycorrhizal fungi. The model plant Arabidopsis thaliana
does not form either symbiosis, making M. truncatula an important tool for studying these processes. The nodule formation is apparently dependent on the flavonoid
s pathway.
It is also an important forage
crop species in Australia
.
sequence of Medicago truncatula, a model legume species. Sequencing the Medicago truncatula genome is expected to facilitate genomics research in legumes, especially the biology of symbiosis
because Medicago truncatula and its symbiotic partner, Sinorhizobium meliloti
, are popular models for symbiosis research.
Sequencing
in Medicago truncatula is taking place at the University of Oklahoma
(US), J. Craig Venter Institute
(US), Genoscope
(France), and Sanger Centre (UK). Partner institutions include the University of Minnesota
(US), University of California-Davis (US), the National Center for Genomic Resources (NCGR) (US) , John Innes Centre
(UK), Institut National de Recherche Agronomique (France), Munich Information Center for Protein Sequences
(MIPS) (Germany), Wageningen University
(Netherlands), and Ghent University
(Belgium). The Medicago truncatula Sequencing Consortium began in 2001 with a seed grant from the Samuel Roberts Noble Foundation. In 2003, the National Science Foundation
and the European Union 6th Framework Programme began providing most of the funding. As of 2009, 84% of the genome assembly has been completed.
Sequencing in Medicago truncatula is based on bacterial artificial chromosome
s. This is the same approach used to sequence the genomes of humans, the fruitfly, Drosophila melanogaster
, and the model plant, Arabidopsis thaliana
. The technique is slower, but typically more accurate, than the now more common approach known as Shotgun sequencing
.
A parallel group known as the International Medicago Gene Annotation Group (IMGAG) is responsible for identifying and describing putative gene sequences within the genome sequence.
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
research. It is a low-growing, clover
Clover
Clover , or trefoil, is a genus of about 300 species of plants in the leguminous pea family Fabaceae. The genus has a cosmopolitan distribution; the highest diversity is found in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes...
-like plant 10–60 cm tall with trifoliate leaves
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
. Each leaflet is rounded, 1–2 cm long, often with a dark spot in the center. The flower
Flower
A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to effect reproduction, usually by providing a mechanism for the union of sperm with eggs...
s are yellow, produced singly or in a small inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
of 2-5 together; the fruit
Fruit
In broad terms, a fruit is a structure of a plant that contains its seeds.The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state,...
is a small spiny pod.
This species has been chosen as a model organism
Model organism
A model organism is a non-human species that is extensively studied to understand particular biological phenomena, with the expectation that discoveries made in the organism model will provide insight into the workings of other organisms. Model organisms are in vivo models and are widely used to...
for legume biology because it has a small diploid genome
Genome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
, is self-fertile, has a rapid generation time and prolific seed production, and is amenable to genetic transformation
Transformation (genetics)
In molecular biology transformation is the genetic alteration of a cell resulting from the direct uptake, incorporation and expression of exogenous genetic material from its surroundings and taken up through the cell membrane. Transformation occurs naturally in some species of bacteria, but it can...
. The genome of M. truncatula is currently being sequenced.
It forms symbioses
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
with nitrogen-fixing
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
rhizobia
Rhizobia
Rhizobia are soil bacteria that fix nitrogen after becoming established inside root nodules of legumes . Rhizobia require a plant host; they cannot independently fix nitrogen...
(Sinorhizobium meliloti
Sinorhizobium meliloti
Sinorhizobium meliloti is a Gram-negative nitrogen-fixing bacterium . It forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis results in a new plant organ termed a root nodule. The S...
and Sinorhizobium medicae) and arbuscular mycorrhizal fungi. The model plant Arabidopsis thaliana
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
does not form either symbiosis, making M. truncatula an important tool for studying these processes. The nodule formation is apparently dependent on the flavonoid
Flavonoid
Flavonoids , are a class of plant secondary metabolites....
s pathway.
It is also an important forage
Fodder
Fodder or animal feed is any agricultural foodstuff used specifically to feed domesticated livestock such as cattle, goats, sheep, horses, chickens and pigs. Most animal feed is from plants but some is of animal origin...
crop species in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
Medicago truncatula Sequencing Consortium
The Medicago truncatula Sequencing Consortium is an international partnership of research laboratories that is decoding the genomeGenome
In modern molecular biology and genetics, the genome is the entirety of an organism's hereditary information. It is encoded either in DNA or, for many types of virus, in RNA. The genome includes both the genes and the non-coding sequences of the DNA/RNA....
sequence of Medicago truncatula, a model legume species. Sequencing the Medicago truncatula genome is expected to facilitate genomics research in legumes, especially the biology of symbiosis
Symbiosis
Symbiosis is close and often long-term interaction between different biological species. In 1877 Bennett used the word symbiosis to describe the mutualistic relationship in lichens...
because Medicago truncatula and its symbiotic partner, Sinorhizobium meliloti
Sinorhizobium meliloti
Sinorhizobium meliloti is a Gram-negative nitrogen-fixing bacterium . It forms a symbiotic relationship with legumes from the genera Medicago, Melilotus and Trigonella, including the model legume Medicago truncatula. This symbiosis results in a new plant organ termed a root nodule. The S...
, are popular models for symbiosis research.
Sequencing
Sequencing
In genetics and biochemistry, sequencing means to determine the primary structure of an unbranched biopolymer...
in Medicago truncatula is taking place at the University of Oklahoma
University of Oklahoma
The University of Oklahoma is a coeducational public research university located in Norman, Oklahoma. Founded in 1890, it existed in Oklahoma Territory near Indian Territory for 17 years before the two became the state of Oklahoma. the university had 29,931 students enrolled, most located at its...
(US), J. Craig Venter Institute
J. Craig Venter Institute
The J. Craig Venter Institute is a non-profit genomics research institute founded by J. Craig Venter, Ph.D. in October 2006. The Institute was the result of consolidating four organizations: the Center for the Advancement of Genomics, The Institute for Genomic Research, the Institute for...
(US), Genoscope
Genoscope
The French National Sequencing Center was created in 1996 in Evry, France. It has been involved in the sequencing of the Human genome....
(France), and Sanger Centre (UK). Partner institutions include the University of Minnesota
University of Minnesota
The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...
(US), University of California-Davis (US), the National Center for Genomic Resources (NCGR) (US) , John Innes Centre
John Innes Centre
The John Innes Centre located in Norwich, Norfolk, England is an independent centre for research and training in plant and microbial science...
(UK), Institut National de Recherche Agronomique (France), Munich Information Center for Protein Sequences
Munich Information Center for Protein Sequences
The Munich Information Center for Protein Sequences is a research center hosted at the Institute for Bioinformatics at Neuherberg, Germany with a focus on genome oriented bioinformatics, in particular on the systematic analysis of genome information including the development and application of...
(MIPS) (Germany), Wageningen University
Wageningen University
Wageningen University and Research Centre is a Dutch public university in Wageningen, The Netherlands. It consists of Wageningen University, the Van Hall-Larenstein School of Higher Professional Education, and the former agricultural research institutes of the Dutch Ministry of Agriculture...
(Netherlands), and Ghent University
Ghent University
Ghent University is a Dutch-speaking public university located in Ghent, Belgium. It is one of the larger Flemish universities, consisting of 32,000 students and 7,100 staff members. The current rector is Paul Van Cauwenberge.It was established in 1817 by King William I of the Netherlands...
(Belgium). The Medicago truncatula Sequencing Consortium began in 2001 with a seed grant from the Samuel Roberts Noble Foundation. In 2003, the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
and the European Union 6th Framework Programme began providing most of the funding. As of 2009, 84% of the genome assembly has been completed.
Sequencing in Medicago truncatula is based on bacterial artificial chromosome
Bacterial artificial chromosome
A bacterial artificial chromosome is a DNA construct, based on a functional fertility plasmid , used for transforming and cloning in bacteria, usually E. coli. F-plasmids play a crucial role because they contain partition genes that promote the even distribution of plasmids after bacterial cell...
s. This is the same approach used to sequence the genomes of humans, the fruitfly, Drosophila melanogaster
Drosophila melanogaster
Drosophila melanogaster is a species of Diptera, or the order of flies, in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly. Starting from Charles W...
, and the model plant, Arabidopsis thaliana
Arabidopsis thaliana
Arabidopsis thaliana is a small flowering plant native to Europe, Asia, and northwestern Africa. A spring annual with a relatively short life cycle, arabidopsis is popular as a model organism in plant biology and genetics...
. The technique is slower, but typically more accurate, than the now more common approach known as Shotgun sequencing
Shotgun sequencing
In genetics, shotgun sequencing, also known as shotgun cloning, is a method used for sequencing long DNA strands. It is named by analogy with the rapidly-expanding, quasi-random firing pattern of a shotgun....
.
A parallel group known as the International Medicago Gene Annotation Group (IMGAG) is responsible for identifying and describing putative gene sequences within the genome sequence.
Mutualism
Researcher Toby Kiers of VU University Amsterdam and associates used Medicago truncatula to study mutualisms between plants and fungi - and to see whether the partners in the relationship could distinguish between good and bad traders/suppliers. By using labeled carbon to track the source of nutrient flowing through the arbuscular mycorrhizal system, The researchers have proven that the plants had indeed given more carbon to the more generous fungus species. By restricting the amount of carbon the plants gave to the fungus, the researchers also demonstrated that the fungus did pass along more of their phosphorus to the more generous plants.External links
- The Medicago truncatula Consortium
- TIGR's link to Genome Browser and Gene Index
- The Medicago Gene Expression Atlas at Samuel Roberts Noble Foundation
- Medicago truncatula eFP Browser Viewer for gene expression data from the Medicago Gene Expression Atlas project, at the Provart Lab's Bio-Array Resource website
- INRA Medicago truncatula Stock Center - France
- http://www.pnas.org/cgi/content/full/101/43/15289
Cannon et al. (2006) Proceedings National Academy Sciences USA, 103:14959-14964. - http://www.plantphysiol.org/cgi/content/full/137/4/1174
Young et al. (2005) Plant Physiology 137: 1174-1181. - http://www.ncgr.org/
- http://medicago.toulouse.inra.fr/
- http://mips.gsf.de/proj/plant/jsf/medi/index.jsp