UA researchers help unlock the genetic secrets of corn

[Source: Deborah Daun, BIO5] - Relying on a genetic "physical map" developed by University of Arizona plant scientists, researchers from Washington University, Cold Spring Harbor Laboratory, Iowa State University, and the UA have completed a working draft of the corn genome. By unlocking the genetic secrets of this crop vital to U.S. agriculture, the researchers have gained information that could ultimately help society deal with drought, global warming, population pressures, and increasing energy needs.

"The impact is going to be tremendous," says Rod Wing, PhD, co-principal investigator on the project and leader of the group that developed the physical map. Wing, a BIO5 member and director of the Arizona Genomics Institute in the UA College of Agriculture and Life Sciences, says that the data contained in the draft genome could be used, for instance, to develop new strains of maize that need less water or can better respond to climate change, as well as to develop strains with higher yields to help feed the planet's growing population. "It will also have an impact on the biofuel industry," Wing says.

The genetic blueprint was announced Feb. 28, 2008 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.

The $29.5 million project was initiated in 2005 and is funded by the National Science Foundation (NSF), the U.S. Department of Agriculture and the U.S. Department of Energy. "Corn is one of the most economically important crops for our nation," says NSF director Arden L. Bement, Jr. "Completing this draft sequence of the corn genome constitutes a significant scientific advance and will foster growth of the agricultural community and the economy as a whole."

The process of unlocking the corn genome began at the UA, where Wing's team, together with UA computer scientist Cari Soderlund, led the development of the genome's physical map by, essentially, taking some 18,000 pieces of genetic material and assembling them in the proper order. Wing’s team also included scientists from the University of Missouri and Rutgers University.

"Imagine that the genome was divided up into pieces and that these pieces are all scrambled in a box, like a puzzle," Wing says. "Using various physical and genetic mapping techniques we put the pieces into the correct order and orientation." Researchers at Washington University in St. Louis sequenced the ordered pieces to create the draft genome, which is available to scientists worldwide through GenBank, an online public DNA database. The genetic data is also available at maizesequence.org.

The draft covers about 95 percent of the corn genome. Scientists from Washington University, the University of Arizona, and Cold Spring Harbor Laboratory will spend the remaining year of the grant refining and finalizing the sequence. "Although it's still missing a few bits, the draft genome sequence is empowering," Wilson explains. "Virtually all the information is there, and while we may make some small modifications to the genetic sequence, we don't expect major changes."

The group sequenced a variety of corn known as B73, developed at Iowa State University 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.

The genetic code of corn consists of 2 billion bases of DNA, the chemical units that are represented by the letters T, C, G and A, making it similar in size to the human genome, which is 2.9 billion letters long. By comparison, the rice genome is far smaller, containing about 430 million bases.

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