Scientists unravel the genetic code of corn

November 20, 2009

Scientists unravel the genetic code of corn

By Georgina Gustin
ST. LOUIS POST-DISPATCH

ST. LOUIS — A team of scientists led by researchers at Washington University has completed a detailed "blueprint" of the genetic structure of corn, a breakthrough in understanding the complex biological underpinnings of one of the world's most important crops.

This detailed decoding of the corn genome, researchers hope, will lead to crops that can better resist drought, withstand other challenging growing conditions, use less fertilizer and yield more corn — critically needed qualities as demand for food and biofuel rises.

The $29.5 million project, launched in 2005 and led by scientists at the university's Genome Center, involved 150 scientists from institutions around the country and was funded by the National Science Foundation and the U.S. Departments of Agriculture and Energy. All of the findings now belong to the public and will be available for any researcher to use.

"It was a true community of people participating, with a goal to get it done," said Iowa corn farmer Pam Johnson, who is also a board member of the Chesterfield-based National Corn Growers Association. "We said that in order to unlock the potential of what the corn plant could mean ..." we need to understand the genetic code, and this should be in the public domain and funded by the government."

Corn is the third cereal crop, after rice and sorghum, to be sequenced — and by far the most challenging.

"It's quite literally the most complex genome that has been decoded, more so than the human genome," said Patrick Schnable, a professor of agronomy at Iowa State University and one of the project's lead researchers.

Corn's genetic structure is especially tricky because the strands of DNA, or chromosomes, are very long and the sequences very repetitive, making it difficult to read. A draft version of the genome that was released by the team last year had mapped 95 percent of the genome.

It took the better part of the last two years to figure out the rest.

"The last bits of these kinds of puzzles are always the most difficult," said Richard K. Wilson, the lead researcher on the project and author of a report to be published today in Science magazine. "Imagine you have a 2-by-2-foot jigsaw, and you've got a little bit of the boat and shore and trees and a lot of blue sky and water. The boat comes together easily because of the detail. The sky takes the longest because all the pieces look the same."

Now that the corn genome has been sequenced, revealing the details of gene placement and function, seed scientists and plant geneticists can more easily steer toward desirable traits and combine them in a single plant, Wilson explained. For example, farmers will be able to extend corn-growing seasons in Texas by producing corn that's more heat-tolerant.

"The bottom line is, they'll be able to make corn farmers more efficient," Wilson said.

That should be good news to many Missouri and Illinois farmers. Illinois produced $8 billion in corn in 2008, ranking it as the second-largest corn-producing state in the U.S. Missouri produced $1.5 billion in corn, ranking it ninth.

The research team that decoded the corn genome has been posting its findings since work began three years ago. And researchers have already been making use of the revelations.

"I had one industry partner come up to me and say: Now we can take what we already know about genetics and lay it on this template that's been elucidated, and we can understand why it works," said Johnson. "It fast forwards their ability to do research and development, to develop new products."

The corn genome that was sequenced was from a strain called B73, developed at Iowa State in the 1970s, which has become the standard research strain.

"What they sequenced was one of the first major lines from the 1970s. It's the blueprint for the modern hybrid," said Stan Dotson, director of breeding at Monsanto. "We can use this work as the standard to assemble and organize our data against our own corn lines. It provides the framework that will help Monsanto and other corn seed companies continue to increase yields for farmers."

The genome sequence will help researchers who work both in traditional breeding and with genetically modified plants.

"The genome sequence is like a computer code," Schnable explained. "Once we have the source code, we can examine it and understand how both traditional breeding and transgenics can improve that source code to develop a plant that might be more drought tolerant or yield more."

The team believes that the corn genome will serve as a model for other cereal crops that are distantly related. Wheat, with its even more complicated structure, could be next for researchers.

Over the last four years, the team also came upon some surprises in their work that have already opened up new avenues for research. For example, they discovered ways to investigate how a corn plant's ancestors passed along certain desirable traits to their offspring, which will help scientists understand how to replicate those traits.

When the researchers looked at the hybrid, they had the genetic material from both plants' "grandparents," leading them to a possible understanding of how certain traits have evolved.

"The genome sequence has led us to new experimental directions," Schnable said. "This has just opened up so many questions. It's a dream come true, from our perspective."

Reprinted with permission of the St. Louis Post-Dispatch, Copyright 2009.