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Key enzyme linked for first time to corn growth.

Corn yields are reduced up to 80 percent if a key enzyme is missing, according to a U.S. Department of Agriculture scientist who says the finding is the first to link the enzyme to seed growth.

A single gene appears to control production of the enzyme, called invertase, based on preliminary studies with a mutant corn that lacks the suspected invertaseproducing gene, says plant geneticist Prem S. Chourey, who is with the Agricultural Research Service in Gainesville, Florida.

Without invertase, the mutant corn's seeds are tiny, shriveled, and never fully developed.

Researchers have long known that invertase is present in corn and other plants, says Chourey. "But we didn't know exactly what role it played. We now know that it is critical for seed growth in corn, and we suspect it may play the same role in other plants."

Invertase breaks down a complex sugar, sucrose, into the simple sugars - glucose and fructose - that the seed needs to fully develop. Plant leaves produce sucrose and transport it to the seed base, the "pipeline" for carrying nutrients to the seed. But sucrose cannot pass through the base and into the seed unless it is first broken down into glucose and fructose, Chourey says.

"We aren't certain why, but we suspect that there is a structural barrier between the base and the seed that prevents sucrose from going into the seed," he says.

In studying a mutant corn, he found that it lacked invertase at the seed base. Without the enzyme to break down the sucrose, the seeds become starved and shriveled and recede from the base.

"We've shown that the seed and base communicate with each other and that invertase is the messenger between the two," Chourey says.

A better understanding of invertase, and the gene that appears to control it, may lead in the long term to genetically engineered crops with better productivity and yields.
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Title Annotation:invertase
Author:Adams, Sean
Publication:Agricultural Research
Date:Jul 1, 1993
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