"Maize is a very exciting genome, both in terms of the roles it has played in contemporary and historic plant genetics and because of its role in agriculture," says Richard K. Wilson, Ph.D., director of the GSC, professor of genetics and lead investigator on the project. "It's a top food source for humans and animals and a leading U.S. export."
The National Science Foundation, the U.S. Department of Agriculture and the Department of Energy allocated a total of $32 million for sequencing maize. The GSC maize genome project will receive $29.5 million of that funding.
"By sequencing the maize genome we'll understand more about the evolution of plant genomes and more specifically the evolution of the genomes of cereals, " says botanist Ralph Quatrano, Ph.D., Spencer T. Olin Professor and chair of the Department of Biology at Washington University's School of Arts and Sciences.
Maize is found in thousands of products in supermarkets and stores. The maize genome's 2.5 billion base pairs in 10 chromosomes make it nearly as long as the human genome, which has 2.9 billion base pairs in 23 chromosomes. When completed, maize will be the largest plant genome sequenced.
Although smaller than the human genome, the maize genome is estimated to contain approximately twice as many genes: 50,000 to 60,000 genes, while the human genome has about 26,000. The maize genome also has large repetitive stretches and regions devoid of genes that will make sequencing challenging.
"It's going to be like trying to put together a jigsaw puzzle with lots of blue sky and very few pieces with landscape," Wilson says. "We'll be working to minimize our data collection on the blue sky and maximize it on the landscape, covering those areas in much greater detail."
Maize is a central focus of ongoing plant genetics research and played a pivotal role in the development of a critical concept of modern genetics. Barbara McClintock, the 1983 winner of the Nobel Prize in Physiology or Medicine, discovered transposons, segments of genetic code that can jump from place to place in DNA, while studying maize in the 1940s and 1950s.
"Transposons are essential to allowing a genome to evolve and develop new genes and new functions," Wilson says. "Much of what we understand about genome structure and evolution we have learned from maize and from the work of McClintock and people who followed her."
Wilson notes that St. Louis has a rich tradition of leadership in agriculture and botanical research, including the headquarters of the Monsanto Corporation, the Missouri Botanical Gardens and the Danforth Plant Sciences Center. Washington University's Division of Biological and Biomedical Sciences includes a graduate program in plant biology with connections to the Botanical Garden and the Danforth Center.
"It's exciting to see this contribution to agriculture come from the St. Louis community," says Robert T. Fraley, senior vice president and chief technology officer for Monsanto Corporation. "Completion of the maize genome will allow agricultural researchers to identify new genes responsible for important traits like yield and drought tolerance, creating opportunities to bring additional value to farmers around the world."
The maize genome will allow botanists to more precisely track the intermingling of genes in hybrid species created to combine advantageous traits. Farmers and botanists currently do this by crossbreeding, sowing the resulting plants, looking for the appearance of those desirable traits in one or more of the resulting cultivars (the plant's world's equivalent to a breed or a strain), and going back to the greenhouse for more crossbreeding.
The genome should make it much more practical to look directly at the DNA of new cultivars to see if they have inherited the desired traits.
"The knowledge gained from this project will ultimately lead to better corn yields," said NSF Director, Arden L. Bement Jr.
Scientists at the GSC will sequence a maize cultivar known as B73 that is commonly used in maize genetics research. Actual sequencing begins on Dec. 1, with the first sequencing information to be made available to the public online starting in early 2006. Scientists estimate the project will take three years.
"What we learn from maize will be applicable to other plant genomes," Wilson notes. "If we successfully work through maize with state-of-the-art sequencing technology and drive the sequencing costs down, then it's going to be easy to think about sequencing other important crops like soybean and sorghum on the heels of maize. Just like the human and mammalian genomes, having other plant genomes sequenced makes the genome that you're currently working on easier to understand and more useful."
Collaborators who will consult on or contribute to the GSC's maize genome work include:
- Rod Wing, University of Arizona;
- W. Richard McCombie, Robert Martienssen, Doreen Ware, Lincoln Stein, Cold Spring Harbor Laboratory;
- Patrick Schnable, Srinivas Aluru, Iowa State University.
The second maize genome sequencing grant, $2.5 million, went to a collaboration of the University of California-Berkeley, the Department of Energy's Genome Institute, the University of Georgia and Stanford University.
These scientists will sequence a chromosome from a different maize cultivar.
Washington University School of Medicine's full-time and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked third in the nation by U.S. News & World Report. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC HealthCare.