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At this point, the linkages they’ve identified are based on inferences drawn from the differences between the wild and mutant plants. To prove that these genes are involved, the MU scientists will have to demonstrate that there are direct physical interactions between the proteins. That bit of biochemistry is technically difficult, Walker says. “But it’s necessary to prove the theory. That’s how science works.”

Walker and Zhang also hypothesize that there are several more genes involved earlier on with creating and transmitting the initial signal for abscission and later on with the actual ungluing of the abscission zone cells.

To find those genes, they’re looking for more Arabidopsis mutations that modify the abscission process. “We still have more question marks and steps. Now, we’re trying to fill in the rest,” Walker says.

Walker is working on that project with a graduate student and two postdoctoral fellows. Their goal, eventually, is to determine the entire genetic and biochemical chain of abscission.

Abscission genes appear to be conserved among plants, so knowledge about Arabidopsis could be applied broadly. Once the genes are known in one plant, scientists can look for similar genes in other plants.

“There might be some differences in the details, but the fundamentals are going to be there,” Walker says. “These genes have been around for a long, long time and if they weren’t important, evolution would have gotten rid of them.” Ultimately, he adds, a more complete understanding of the genetics of abscission could increase general understanding of how genes perceive and respond to chemical signals, with applications not only to plants but to human biology as well.

Whatever scientists find, it will take much less time than it would have when Walker started his career more than 20 years ago. He marvels at how technology has speeded up research. Instead of looking at one gene at a time, whole genomes are open to study.

“We’re making discoveries a lot faster then we used to,” he says. Walker got his first exposure to the science of biology, not entirely positive, while growing up in Phoenix, Arizona. For many years, he spent his summers working for his father, a veterinarian. “That pretty well convinced me I didn’t want to be a vet or a doctor,” he says.

But as an undergraduate at Arizona State University, Walker worked in the laboratory of a plant biologist and became fascinated with the biochemistry of plants. As a graduate student at the University of Georgia, he became interested in genetic signaling. And after he earned his doctorate in 1985, Walker went to Australia to work with a leading research group studying gene transcription.

In 1987, Walker joined the MU faculty. Soon after coming to the University he discovered receptor genes in plants, a finding that opened up a whole new realm of research. “These looked like receptors in us, like insulin receptors,” Walker says. “People really didn’t think they were in plants. They didn’t think plants used protein signals.”

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Illumination home. Spring 2009 Table of Contents.