Syndicate content

Corn Genome Sequence Is Detailed

A four-year, multi-institutional effort culminated today in publication of a landmark series of papers in the journal Science, revealing in unprecedented detail the DNA sequence of maize (Zea mays). Maize, or corn, as it is commonly called by North American consumers, is one of the world's most important plants and the most valuable agricultural crop grown in the United States, representing $47 billion in annual value. The sequence spans 2.3 billion DNA base-pairs and contains some 32,500 genes, or about one-third more than the human genome, according to the team that assembled it over the last four years. This version of the maize genome--taken from a variant called B73--is important, in part, because it is regarded by the scientific and agricultural communities as a "reference" version. It represents a significant filling-in of gaps in a draft maize sequence announced a year and a half ago, but more importantly, comes with what amounts to a detailed reference manual, a set of comprehensive annotations. "What's important about the maize project," said Dr. W. Richard McCombie, a Cold Spring Harbor Laboratory (CSHL) professor, a co-principal investigator on the maize genome project, and a pioneer in genome sequencing efforts, "is that it provides a reference DNA sequence for the most important agricultural crop in the U.S., making it much easier for people to look at the many variants of different strains or 'accessions' of maize." New sequencing technologies, just now becoming commercially viable, will now be used to "analyze other maize strains by comparing them to this one--albeit at dramatically lower costs and accelerated speeds," Dr. McCombie noted. Another of the co-project leaders from CSHL, Professor Robert Martienssen, put the maize sequencing project into historical perspective. Professor Martienssen, a world leader in research on transposons--bits of DNA that copy and insert themselves randomly across the chromosomes--noted that transposable elements are found in all organisms, "but were discovered in maize more than 60 years ago," by CSHL's Barbara McClintock, who was honored with a Nobel Prize for the discovery in 1983. "It is a remarkable achievement to now be able to visualize transposons in such detail in the maize genome sequence," Dr. Martienssen said. Senior author of the maize sequencing article was Dr. Richard Wilson of the Washington University School of Medicine. "Seed companies and maize geneticists will pounce on this data to find their favorite genes," said Dr. Wilson. "Now they'll know exactly where those genes are. Having the complete genome in hand will make it easier to breed new varieties of corn that produce higher yields or are more tolerant to extreme heat, drought, or other conditions." In research carried out in parallel with the sequencing effort, the CSHL team also helped generate the first so-called "HapMap" of maize. The HapMap, a shorthand for haplotype map, gauges diversity in the maize genome by comparing 27 distinct genetic lines of the plant with the reference version. A human HapMap, prepared in conjunction with the Human Genome Project, has revealed important linkages between genetic variations and risk for major diseases in ethnically and geographically distinct human populations. The maize HapMap article authors noted that their survey of genetic diversity provides a foundation for uniting breeding efforts across the world and for dissecting complex traits through genome-wide association studies. The map should pave the way to significant improvements in a plant that is a major source of food, fuel, animal feed, and fiber around the world. New techniques may allow breeders and researchers to use the genetic variation to identify desirable traits and create new varieties that were not easily possible before. The landmark maize genome articles were published in the November 20 issue of Science. [Press release 1] [Press release 2] [Press release 3] [Press release 4] [Science abstract 1] [Science abstract 2] [Science abstract 3] [Science abstract 4]