Purdue News
Purdue News
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December 1993 Purdue achieves first genetic transformation of sorghumWEST LAFAYETTE, IND.–The first genetically engineered sorghum plants have been developed by a team of scientists at Purdue University and two other laboratories. The scientists were able to move a marker gene into two genotypes of sorghum using a procedure known as microprojectile bombardment. The results of the research will be published this month in The Proceedings of the National Academy of Science. Although only a test gene has been used in the research so far, scientists say they now can use genetic engineering techniques with sorghum to transfer traits such as resistance to disease or pests. "This allows sorghum breeders to overcome obstacles," says Ray Bressan, Purdue professor of horticulture. "There's a tremendous opening up of possibilities. It allows the breeders to use imaginatively a vast untapped resource of genes when developing new varieties." Mike Hasegawa, Purdue professor of horticulture and another member of the eight-person team, says that although sorghum isn't a major crop in the United States, this research could change that. "You can grow sorghum with a lot less intensive input than corn," he says. That would mean fewer pesticides, which would result in less expensive feed grain for farmers. Because corn and sorghum are cereal crops that are similar genetically, the science also may benefit corn farmers, says John Axtell, Purdue's Lynn Distinguished Professor of Agronomy. "Because sorghum appears to be easier to genetically transform than some other cercal crops, we should be able to develop techniques on sorghum first, and then try to apply them to crops such as corn," Axtell says. Sorghum is fifth among cereals in production worldwide, and is the primary food source for 3OO million people in the semi-arid regions of Africa and Asia. Although sorghum isn't grown as a food product in America, it is still important in the United States as a livestock feed. "The western states would not have a cattle industry without it," Axtell says. "It's also important to farmers in parts of southwestern Indiana and southern Illinois." Cereal plants are difficult to genetically transform. Genetic engineering of plants is often done by using a vector–a biological Trojan Horse such as a virus–to move the DNA into the cells, or by allowing the cell protoplasts (cells without the cell walls) to absorb the genetic material. But no natural vector for sorghum is available, and it is difficult to grow cereal plants from protoplasts. In this case, the researchers use a device powered by pressurized helium and commonly referred to as the gene gun to move the genes into single plant cells that grow into plant embryos. In this technique, called microprojectile bombardment, genes that the scientists want to move into the plant cells are placed as a coating on micro-particles of gold or tungsten. The particles are placed on a minuscule plastic disk. The disk is loaded into a tube and fired down at a screen above the plant cells. The screen stops the disk but allows the particles to fly off and penetrate the cells. "It's like you had something on the roof of a car, and the car hits a four-foot wall. Whatever's on the roof is going to go flying," Bressan says. The cells absorb the new genetic material fired into them and incorporate the new piece of DNA into their chromosomes. The gene the researchers moved into the sorghum plants gives the plants resistance to the herbicide bialaphos, which normally kills sorghum. To determine whether the sorghum plants had been genetically transformed, the researchers sprayed the plants grown from the embryos with the herbicide. Those plants that survived had successfully received the new gene. "Herbicide resistance is not a trait we would want to move into sorghum normally; it was just used as a marker gene for this experiment," Bressan says. "These plants will never leave the greenhouse." Although Ana Casas, one of the primary investigators, understands fully the science of what the team has created, she still displays wonderment at the accomplishment. Upon viewing a healthy and productive genetically altered sorghum plant in a greenhouse, she exclaims: "It's like magic! It really worked!" Casas is a visiting scholar at Purdue from Spain's Estacion Experimental Avla Dei. Hasegawa says although in hindsight the process seems straightforward enough, there were discouraging moments: "A voluminous amount of the research was not successful, which is difficult on the psyche of scientists. But the researchers focused themselves, concentrated on the research and found the optimum conditions that allowed this to work." Casas says researchers will continue to work to refine the technique. "We're hoping to make the process more efficient so people can use it in applied breeding programs," she says. The project to produce transgenic sorghum began 2 1/2 years ago with funding from Pioneer Hi-Bred International Inc., the McKnight Foundation and the U.S. Agency for International Development through the International Sorghum and Millet Collaborative Research Support Program. Scientists at Pioneer and the University of Lodz in Lodz, Poland, contributed to the project. NOTE: A black-and-white photograph. Contact Purdue News Service, (765) 494-2096. Contact Purdue News Service (765) 494-2096 or purduenews@purdue.edu
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