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Tomato Research: Ripe for the Picking

December 1996

Tossed, chopped, or pureed, the well-loved tomato is one of the more frequently used fruits in American diets. It's also the subject of basic research funded through NSF's Directorate for Biological Sciences. The separate findings of three plant biologists will not only help gardeners, but will aid in the study of other plants and provide insights into areas that are seemingly unrelated to agriculture.

Good tasting tomatoes are sweet, according to many tomato-lovers. But the real key, says Pamela Dunsmuir of the DNA Plant Technology Corporation in Oakland, California, is acid.

Recent advances in genetics and molecular biology make it feasible to alter fruit acidity, explains Dunsmuir. Her experiments will help determine whether biologists can modify citric and malic acid (two major organic acids in tomatoes) via gene manipulation. To date, Dunsmuir has isolated the gene for one tomato's malic acid, and has prepared 100 kinds of genetically altered tomatoes. She expects her research company and its affiliated commercial branch to soon produce "new tomatoes with enhanced flavor arising from altered acidity."

For Rod Wing of Texas A&M, the question isn't just how the tomato tastes, but when it can be picked.

Wing is investigating the phenomenon of abscission, the process by which plants shed organs. In terms of ecology and adaptation, he says, abscission gives plants flexibility in dealing with stresses, injuries, and pollination failures. "And economically," he adds, "the study of abscission becomes very important in terms of knowing when to harvest mature fruit."

Abscission happens in three stages. First, the plant develops a region where the abscission will occur. Next, the fruit separates from the plant. And last, the plant forms a protective layer of cells over the "stump" left behind by the fruit's separation.

Understanding this process will be helpful to many types of agriculture, says Machi Dilworth, director of NSF's integrated plant biology program. "This process is at work everywhere we look, from picking fully ripened tomatoes, to harvesting cotton."

Meanwhile, Ruth Stark of the City College of New York, is investigating the tomato's outer skin and finding applications outside of agriculture.

Stark's goal is to understand the chemical structures that protect the fruit from bacteria and fungi. The skin is made up of waxes that provide "waterproofing" with polymers. Stark is studying how these polymers are linked, how they are embedded within wax or cell-wall matrices, and how their molecular "architecture" is related to their functions.

Her ultimate goal is to design methods to improve the plants' natural protective process. "And," she says, "since polymer mixtures are involved in tomato skin membranes, this research may have future applications in the design of synthetic coatings for waterproofing and also for the development of adhesives."

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