ARDMORE, Okla. — Discovery of a protein that appears to play a key role in moving disease resistance through a plant, and eventually could find use in genetically introducing disease protection in crops, has been reported by an international team of scientists, including researchers from the Noble Foundation in Ardmore, Okla. Their groundbreaking work was published in the scientific journal Nature on Sept. 26.

Other scientists among the team are from the University of Toronto, the John Innes Center in Norwich, UK, the Salk Institute in La Jolla, Calif., and the University of Edinburgh, Scotland.

Dr. Robin Cameron, with the Department of Botany at the University of Toronto, did much of the early work in finding the protein, called DIR1, while working jointly as a postdoctoral fellow at the Noble Foundation and at the Salk Institute.

Dr. Richard A. Dixon, Noble Foundation Plant Biology Division director, in whose lab Cameron worked on the project during 1994 and ’95, said the importance of DIR1 is that it appears to be the gene responsible for the movement of a signal that induces disease resistance throughout the plant, starting from where the infection first occurs.

"If you infect one leaf of a plant with a bacterium to which the plant is resistant, there will be local disease resistance response on that particular infected leaf," Dixon said. "If you come back some time later and infect another leaf, you’ll find that resistance is greatly enhanced throughout the plant." Better yet, he adds, it builds resistance to other diseases in the process.

The name for the gene comes from defective in induced resistance (DIR). Approximately 11,000 mutant lines of thale cress (Arabidopsis thaliana), a common weed found in many parts of the world, were screened by Cameron over many months. She looked for plants that exhibited normal resistance to a single infection but which were incapable of developing enhanced resistance to subsequent infection. One mutant plant line was found that could not develop systemic acquired resistance (SAR) to an introduced bacterial disease, due to a mutation in a single gene — DIR1. The DIR1 gene, then, appears to be a key component of the transmittal of the signal responsible for SAR.

Several genes have been identified through research as being necessary for local disease resistance, but this is the first time a long-distance signaling gene has been identified that is distinct from the local disease resistance genes, Dixon said.

Understanding how disease resistance is spread in plants could provide major breakthroughs in developing immunity against a variety of different diseases. Developing such genetic protection in crops could, in turn, reduce the need for chemical pesticides while maintaining high production.

The research was funded by the Noble Foundation, Agritope, the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation and the UK Biotechnology and Biological Sciences Research Council.

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Photo:
Dr. Richard A. Dixon

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The Samuel Roberts Noble Foundation, headquartered in Ardmore, Okla., is a non-profit organization conducting agricultural, forage biotechnological, and plant biology research; providing grants to numerous non-profit charitable, educational and health organizations; and assisting farmers and ranchers through educational and consultative agricultural programs.

To learn more, visit the Noble Foundation Web site at http://www.noble.org.

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