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Scientists modify corn to bulk up its sugary biomass

By Ryan C. Christiansen
Web exclusive posted March 6, 2009, at 11:02 a.m. CST

Scientists at the College of Agricultural, Consumer, and Environmental Sciences at the University of Illinois at Urbana-Champaign have genetically modified corn so that it grows larger with fewer grains, more leaves, and a bigger stalk full of sugars. The genetic modification might help scientists to engineer corn and its relatives to produce bulkier, more sugary biomass for energy crops.

"What we've done with corn could also apply to sorghum, sugarcane, miscanthus, switch grass, and other plants related to corn that are being talked about for biofuels," said Stephen Moose, associate professor of maize functional genomics and genetics at the University of Illinois. "We may have some potential there."

Moose said the gene responsible for bulkier corn is glossy15, a name that describes the gene's role in giving corn seedlings a waxy coating. The gene also slows down how quickly the plant matures. "This gene is related to a family of genes that are known to control the rate of development," Moose said. "We knew that if you reduce the function of the gene in corn, that the plant progresses to its adult phase faster. We figured if we increased the activity of the gene it should grow more slowly. We did that by taking the DNA sequence from corn and then put back into the corn extra copies of the gene."

Putting more glossy15 into the DNA of corn had the expected effect: it slowed down the growth of the plant. "But then it also had an unexpected effect," Moose said. "Even though it slows the rate of growth, [the plant] flowers much later, and so the plant just keeps growing and growing and growing through the season instead of stopping in mid-summer when it's time to put seeds on. And so there aren't as many seeds and, because you have a bigger plant that has less grain, it doesn't have a place to put the nutrients that it has accumulated over the season. That's why the carbon accumulates as sugar, because it doesn't go into the grain where it normally would be packaged as starch."

Moose said reducing the amount of grain a corn plant produces to make a bigger plant is not a new idea. "The difference in our case is that we have a single gene that does it," he said, "and it's sort of very predictable in what it does and we know exactly what gene it is."

The next phase for the study is to compare genetically modified commercial breeds of corn with tropical maize, which naturally grow bigger and produce more sugar when moved to northern latitudes with longer summer days. "What we think is happening is that the gene that we've been working with taps into the same developmental process that makes these tropical lines bigger and produce more sugar," Moose said. "I think what we found is that this gene is better than the tropicals in some ways, because with the tropicals, you get the good effects of more biomass, but they don't have the right disease resistance or they may have other things that sort of come along that are not as desirable."

Moose said if a company were to consider using glossy15-gene-modified corn in commercial agriculture, there would be a three- to five-year wait for the government to approve the hybrid. "Because it does have some grain, there is the potential that it could end up in the food supply," he said, "and so we would have to go through the same process as if it was being marketed for food."
 

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