Fluorescent Corn Components Suggest Processing Improvements

Researcher Paul Scott holds corn kernels created with the GFP technology (yellower kernels) interspersed with normal corn.
AMES, Iowa — Researchers at Iowa State University have used a Nobel Prize-winning genetic technology to expand the understanding of milling corn. When corn is milled, or ground, its three primary tissues combine. That complicates matters for end-users who want separate parts, such as the protein-and oil-rich part for feed or the starch for making alcohol. If only the embryo, starch-rich endosperm or the pericarp covering the kernel could be made to stand out in the ground corn it would be easier to select the tissues of interest. Scientists did just that by developing tissue markers for transgenic corn lines using green fluorescent protein (GFP). Geneticist Paul Scott, who works in the U.S. Department of Agriculture's Agricultural Research Service (ARS) Corn Insects and Crop Genetics Research Unit located at Iowa State; Lawrence Johnson, director of the Center for Crops Utilization Research; Kan Wang, director of the Plant Transformation Facility; Charles Glatz, professor of chemical and biological engineering and former interdepartmental genetics graduate student Colin Shepherd, teamed up for the corn project. "We developed a tool to allow us, for the first time, to quantify directly the amounts of germ (embryo) and endosperm in milled products," Johnson said. Previously, an analysis was indirect; based on oil content. Researchers assumed that most of the oil is in the embryo. The direct measurement using the GFP technology made it possible to more accurately measure contamination of these tissues in the different milled products. "Once you have a means to measure the different parts then you could use the data to improve the milling process," Johnson said. "The changes could include adjusting grain tempering time, degerminator selection, roller mill settings and sieve sizes." The scientists incorporated the GFP markers into the either the embryo or the endosperm and used a device that measured lightwave emissions from the fluorescent corn tissues. One corn line's endosperm contained 100 percent of the GFP fluorescence. After hand-dissecting the transgenic kernels and identifying GFP concentrations in the pericarp, embryo and endosperm tissues, they had baseline levels to use for identifying different tissues during the fractionation, or milling, process. The researchers determined GFP fluorescence levels for each part by being able to easily identify the mix of tissues in each. "The GFP technology has revolutionized biology," Scott said. "It helps us understand how transgenes function and allows us to implement transgenic technology in a safer way." He expected that it will expand knowledge about how corn genes interact with genes introduced into corn plants. The three researchers who developed the GFP technology used by Scott and his colleagues were presented the Nobel Prize in chemistry Dec. 10. Osamu Shimomura, Marine Biological Laboratory and Boston University Medical School; Martin Chalfie, Columbia University, and Roger Y. Tsien, Howard Hughes Medical Institute, University of California, isolated the protein from a species of jellyfish.