Researchers Unveil Draft Sequence of Corn Genome

25 February 2008

DNA from the human and corn (maize) genomes contain dispersed arrangements of genes (green in maize.) The number and size of repeated DNA segments (brown) between the genes in maize presented unique challenges for the sequencing team. Click to enlarge. Credit: Nicolle Rager Fuller, NSF

A team of scientists led by Washington University in St. Louis have completed a working draft of the corn genome, an accomplishment likely to accelerate efforts to develop crop varieties to meet society’s growing demands for food, livestock feed and fuel.

The genetic blueprint will be announced on 28 February by the project’s leader, Richard K. Wilson, Ph.D., director of Washington University’s Genome Sequencing Center, at the 50th Annual Maize Genetics Conference in Washington, D.C.

This first draft of the genome sequence is exciting because it’s the first comprehensive glimpse at the blueprint for the corn plant. Scientists now will be able to accurately and efficiently probe the corn genome to find ways to improve breeding and subsequently increase crop yields and resistance to drought and disease.

—Richard Wilson

The $29.5 million project was initiated in 2005 and is funded by the National Science Foundation (NSF), the US Department of Agriculture and the US Department of Energy.

The team working on the endeavor, including scientists at the University of Arizona in Tucson, Cold Spring Harbor Laboratory in New York and Iowa State University, has already made the sequencing information accessible to scientists worldwide by depositing it in GenBank, an online public DNA database. The genetic data is also available at maizesequence.org.

The draft covers about 95% of the corn genome, and scientists will spend the remaining year of the grant refining and finalizing the sequence.

The group sequenced a variety of corn known as B73, developed at Iowa State decades ago. It is noted for its high grain yields and has been used extensively in both commercial corn breeding and in research laboratories. The genome will be a key tool for researchers working to improve varieties of corn and other cereal crops, including rice, wheat and barley.

There’s a lot of great research on the horizon. The genome will help unravel the basic biology of corn. That information can be used to look for genes that make corn more nutritious or more efficient for ethanol production, for example.

— Ralph S. Quatrano, Ph.D., the Spencer T. Olin Professor and chair of Washington University’s Department of Biology

Corn is only the second crop after rice to have its genome sequenced, and scientists will now be able to look for genetic similarities and differences between the crops, Quatrano adds.

The genetic code of corn consists of 2 billion bases of DNA. By comparison, the rice genome is far smaller, containing about 430 million bases. About 80% of corn’s DNA segments are repeated, and corn also has 50,000 to 60,000 genes, roughly double the number of human genes. The number and size of repeated DNA segments between the genes in corn presented unique challenges for the sequencing team. Mobile genes, or transposons, make up a significant portion of the genome, further complicating sequencing efforts.

The United States is the world’s top corn grower, producing 44% of the global crop. In 2007, US farmers produced a record 13.1 billion bushels of corn, an increase of nearly 25% over the previous year, according to the US Department of Agriculture. The 2007 production value of corn was estimated at more than $3 billion. Favorable prices, a growing demand for ethanol and strong export sales have fueled an increase in farmland acreage devoted to corn production.