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Hutchinson Center Receives $1.2 Million From National Science Foundation to Study Plant Genetics

New strategy obtains useful genetic mutations in plants with no transgenic manipulations

The Fred Hutchinson Cancer Research Center has received a $1.2 million first-year grant from the National Science Foundation to implement a new strategy for obtaining plants with desirable genetic mutations. The strategy, called TILLING, will be applied to genes of Arabidopsis thaliana, a small flowering member of the mustard family used as a model system for plant genetic studies.

Using the TILLING method, researchers will induce and analyze mutations rapidly and on a large scale without introducing genetically modified material into the organism. Applying the TILLING strategy to agriculturally important plants may let scientists identify mutations that produce desirable changes, says project leader Steven Henikoff, Ph.D., a member of the Hutchinson Center's Basic Sciences Division. A Hutchinson Center graduate student in Henikoff's lab, Claire McCallum, developed the TILLING method.

Collaborating on the project is co-investigator Luca Comai, Ph.D., an associate professor of botany at the University of Washington. Comai will provide plant molecular biology expertise and greenhouse space for the 10,000 Arabidopsis plants needed for the intitial project setup. The work will be performed at the Institute for Systems Biology in Seattle, which will host the project through the Hutchinson Center.

"All flowering plants are very closely related evolutionarily, and therefore in DNA sequence," Henikoff says. Therefore, what is learned about Arabidopsis will benefit studies of all plants.

While Arabidopsis might seem a curious organism to be found at a cancer research center, Henikoff expects TILLING to be useful for inducing genetic mutations in other organisms, including mice and the roundworm C. elegans, both model systems used at the Hutchinson Center to study the basic mechanisms of cancer.

The basic strategy for TILLING in Arabidopsis involves exposing the plant seeds to a chemical that induces point mutations, or single-base changes, in the plant's DNA. Plants are then grown from these mutated seeds, and the DNA is isolated from each. The individual DNA samples are then pooled, just like ingredients for a recipe are combined in a mixing bowl. This allows DNA from multiple plants to be analyzed at once.

Next, a method called polymerase chain reaction, or PCR, is used to make many copies of DNA to be used for more detailed analysis. The entire PCR product is then heated and cooled, which causes the zipperlike DNA strands to separate and then randomly come back together. Any imperfect pairings indicate an area of genetic disruption, which can be analyzed further to pinpoint the exact genetic mutation.

TILLING has several advantages over other methods for making mutations: It yields a much wider range of mutants than other currently available strategies, it can be automated, and it is applicable to any gene and any organism.

CONTACT: Kristen Woodward
(206) 667-5095

Sept. 21, 2000