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Plant molecular geneticist Susan Wessler studies the role of transposable elements (or transposons) in generating genetic diversity. Transposons are mobile pieces of DNA that are distinct from genes. Wessler’s lab discovered a new class of transposons, called miniature inverted repeat transposable elements. Her work focuses on the role of transposons in plant genomes and the modified gene functions needed for evolution. Born in New York City, Wessler earned her B.A. at the State University of New York at Stony Brook in 1973, and her Ph.D. at Cornell University in 1980. Wessler completed a postdoctoral fellowship with the Carnegie Institute of Washington, working on model organisms for maize and grasses. Wessler is currently the University of California President's Chair in the Department of Botany and Plant Sciences at the University of California, Riverside.
Listen to the Interview (requires free RealPlayer software):
Wessler talks about her introduction to the world of science at the Bronx High School of Science. Though her parents steered her toward becoming a doctor, Wessler began taking courses in biochemistry and organic chemistry and discovered her love of research. After graduating college, she wrote ad copy, deciding she was not meant for the “ivory tower” of academics. Two years later, she decided to go back into science and entered Cornell University to study biochemistry. (10 minutes)
While completing a postdoctoral fellowship at the Carnegie Institute of Washington, Wessler met Nobel Prize winner Barbara McClintock,and became fascinated with her discovery of and research on transposons. In trying to better understand transposons, Wessler studied McClintock’s work with transposons and bacteria. (10 minutes)
Before McClintock discovered transposons, the evident traits of plants like corn, such as the different patterns of kernel pigmentation, were all attributed to genes. However, most of the genome is mostly comprised of non-genes; much of it is made up of transposable elements. Wessler talks about how she continued to be heavily influenced by McClintock’s research on pigment genes in corn, and how she began studying not the pigment layer, but the endosperm (the thick, starchy inside of the kernel), where the transposable elements are easier to isolate. Also, Wessler discusses why she chose a more manageable system of isolating transposons in order to better understand the maize genome. (11 minutes)
Wessler’s lab takes plant genomes, identifies repeated genomic sequences, and looks for ones that have active transposons. The DNA elements have an enzyme called transposase; if scientists can isolate the transposase from a plant organism, they can keep track of the elements by the enzyme. McClintock believed that extra matter in the genome was possibly responsible for rapid change in the genome. The changes in the genome were induced by external events -- for example, a sharp increase in a climate’s temperature -- which McClintock called “genomic shock theory.” These changes are thought to be the result of the actions of transposable elements, and are the focus of Wessler’s work. (9 minutes)
While the unknown material in a genome is often referred to simply as “junk” DNA, Wessler explains that researchers still have no proof that it does not have a purpose. Some researchers think that the transposons actually cause evolution. Wessler has spent much of her career trying to find a system where such change is occurring; in the last two years, she has found a transposable element in rice that she can find only in one strain. One of the reasons Wessler works with rice is that it has “user-friendly elements.” Studying transposable elements in plants could lead to more specific agricultural research. (11 minutes)
Wessler also talks about her lab’s current interests in rice and irises, including population tagging. Now that technology is easily accessible to her lab, the amount of work takes half the time -- what used to take several years now takes several months. She incorporates biochemistry, population biology and other disciplines into her research. Wessler says she sees herself as the conductor of her lab’s orchestra. She also says she considers herself fortunate to be in academia, since she has been able to focus on one area for the past 20 years. (11 minutes)
Last Updated: 06-27-2006
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The audio files linked above are part of the National Academy of Sciences InterViews series. Opinions and statements included in these audio files are those of the interviewee and do not necessarily reflect the views of the National Academy of Sciences.