Writer: Austin Craig and Lacey Daniell
For years, farmers have put chemical fertilizer on soil in an attempt to enhance levels of phosphorus and nitrogen -- nutrients that are essential for plant growth. What they didn't realize was that nature already had a system in place to provide plants with these nutrients.
That system involves different types of fungi that have what is called a symbiotic relationship with plants. Plants provide the fungi with carbon that they extract from carbon dioxide in the atmosphere by means of photosynthesis, and the fungi provide plants with nutrients from the soil such as phosphorus and nitrogen.
Scientists have known about the existence of symbiotic fungi since the early 1900s, but only in the last decade has the technology become available to study their genetics and biochemistry. Researchers estimate that 80 percent of plants are colonized by beneficial fungi.
Now, researchers at New Mexico State University are leading an international effort to study the genome of a fungus called Glomus intraradices. Their efforts could help farmers grow crops without chemical fertilizers and provide a means to remove carbon dioxide from the atmosphere. Carbon dioxide is a "greenhouse gas" generated by the burning of fossil fuels that is commonly associated with global warming.
Glomus is a white fungus that can been seen with the naked eye. It lives within the roots of many important plants, including alfalfa, corn, rice and wheat, as well as trees such as aspen, cottonwood and poplar.
Peter Lammers, an associate professor of chemistry and biochemistry at NMSU, has been studying Glomus for five years and has already sequenced 5 percent of its genome in his laboratory at NMSU. The term genome refers to the complete set of genes found in all the chromosomes in a plant, fungus or animal. Genes harbor the information needed to synthesize the proteins that determine the characteristics and functions of organisms.
Lammers' expertise with Glomus has led the U.S. Department of Energy to select him to chair an international committee that will analyze the entire genome of this important fungus. The Department of Energy is interested in Glomus, as well as other plants, as part of its mission to study climate change and carbon management.
The DOE will sequence the genome using powerful automated instruments and supercomputers at its Joint Genome Institute in Walnut Creek, Calif. NMSU will provide the genetic material to be used in the sequencing, and Lammers expects that the institute's computers will be able to sequence the genome's 15 million base pairs -- which form the basis of the genetic code -- in about six weeks. Lammers and colleagues from Michigan State University, Cornell University, Oak Ridge National Laboratory in Tennessee, the University of Lausanne in Switzerland and CNRS in Dijon, France, will then analyze the data generated.
While the genome is being sequenced, Lammers and his colleagues will apply for further funding from the DOE for experimental studies on the functions of the genes they find.
"Once we have access to this genome sequence, we can begin to figure out why Glomus cannot grow without colonizing a plant, and how we might be able to mass produce the spores so that they could be re-introduced for agricultural purposes," Lammers said.
Lammers said developing agricultural practices using the fungus could help bring back low-input agriculture and enable cultivation of arid or semi-arid lands because the fungus promotes drought resistance in the plants it colonizes.
Eventually, Lammers said, researchers may be able to identify which symbiotic fungi are best suited for various crops, whether they be orange trees in Florida, wheat in the Pacific Northwest or chilies in New Mexico.
Researchers also hope to get enough information about symbiotic fungi to model and manipulate carbon dioxide removal from the atmosphere. Scientists estimate that on a global basis Glomus intraradices and other symbiotic fungi like it return 5 billion tons of atmospheric carbon to the soil each year. However, the current practice of adding fertilizer to cultivated fields suppresses the development of symbiotic fungi.
Already, Lammers said, researchers have learned an important lesson. "You can use fertilizers to go beyond what nature has evolved to sustain plant nutrition and stimulate yield, but there is a long-term cost to the soils via the loss of beneficial fungi," he said..
© 2013 New Mexico State University Board of Regents
NMSU - All About Discovery!