Cloning the Gene for a Natural Insecticide

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The work of Helen Riaboff Whiteley, UW microbiology professor, laid the foundation for the genetic engineering of insect-resistant plants.

Whiteley was the first to clone the gene for the insecticidal protein that occurs naturally in a common soil bacterium called Bacillus thuringiensis (Bt). This breakthrough contributed to commercial development of Bt as a biological control agent that is now used extensively against a wide variety of insects.

Born in Harbin, China, of Russian parents, Whiteley became a naturalized U.S. citizen and later earned a Ph.D. in microbiology from the UW in 1951. After a two-year postdoctoral fellowship in California she joined the UW faculty, where she was appointed full professor in 1965. After her death in 1990, the Helen R. Whiteley Endowed Fellowship was established in honor of her scientific achievements to support outstanding graduate students in microbiology.

Whiteley is remembered by colleagues especially for her keen interest in the processes by which genes are regulated, and her knack for selecting good experimental systems for studying those processes. Her early work on the genes of bacterial viruses led to an understanding of how promoters—the genetic "start buttons" of these viruses—initiate the process of transcribing genetic information.

To extend the work, "she made the insightful decision to study the expression of the crystal protein genes in subspecies of Bacillus thuringiensis," says James J. Champoux, UW microbiology professor. "This turned out to be a brilliant choice for several reasons." First, when the gene is turned on, it is expressed to very high levels, making experimental analysis very easy. Secondly, the gene is only turned on during the time when Bt is converting itself into a spore, the dormant stage in its life cycle. This meant that the system could be easily manipulated to study the regulation of transcription during a staged cycle of development.

Thirdly, the proteins are produced in such quantities that they actually crystallize inside the spores. That fact facilitated the collection and purification of the crystal proteins. "Fourth, she guessed correctly that the gene for the crystal protein would be located on an extrachromosomal element called a plasmid, rather than on the larger bacterial chromosome. In the end, this made the job of cloning the gene much easier," notes Champoux.

And finally, the crystal protein is toxic to many insect species. In a seminal paper, Whiteley and colleagues described the use of genetic engineering techniques to insert the Bt gene for the crystal protein into a plant, rendering it resistant to a leaf-chewing insect.footnote 1

Champoux recalls seeing the effects with his own eyes. "It was just remarkable," he exclaims. "One plant was chewed to bits, and the other [with the inserted Bt gene] was as healthy as can be--the insects just wouldn't eat those plants."

Following "the highest standards for good science," Whiteley had "a wonderful sense for seeing patterns and important relationships," reflects Champoux. "For her work and her ability to train young scientists, she was held in the highest regard by her colleagues around the world."

  1. Plant Physiology, 85, 1103 (1987).

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