No-Wilt Flowers -- and No-Spoil Veggies?
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Fruits that ripen on schedule, vegetables that last longer in the refrigerator, and cut flowers that keep their beauty and fragrance for many days may soon be a reality, thanks to research conducted by National Science Foundation funded scientists.
Researchers Eric Schaller and Anthony Bleecker of the University of Wisconsin have identified the first plant hormone receptor, responsible for a variety of important processes in plants. Results of their research are published in the December 15, 1995 issue of the journal Science. The knowledge will allow biotechnologists to fine tune developmental processes in plants that are regulated by a plant hormone called ethylene.
Growth and development in plants and animals is controlled by chemical signals referred to as hormones or growth factors. The mechanisms by which these signals are recognized, and how this information is processed by cells, have been the subjects of massive scientific efforts over the last few decades. Now, thanks to modern genetic research, the first hormone response pathway in plants is being revealed to scientists.
"The plant hormone ethylene controls such processes as the ripening of fruits like apples, bananas, and tomatoes," says Bleecker. "It's responsible for the shedding of leaves by trees in autumn, and the dropping of fruits from trees before they're ready to be picked. It may also be responsible for the short shelf-life of many vegetables, as well as the wilting of cut flowers." Now the mustard weed Arabidopsis thaliana, commonly used in plant genetic research, is providing researchers like Schaller and Bleecker with information on the genes involved in cellular responses to ethylene.
The hunt for the genes began more than eight years ago, with the identification of mutant forms of Arabidopsis that lacked the ability to respond to ethylene. Schaller and Bleecker's research on a gene called ETR1 has now proved that this gene "codes for" the ethylene receptor in Arabidopsis. But what about other plants? Does a similar mechanism work in roses or tomatoes?
The answer, for tomatoes at least, also appears in this issue of Science. Botanist Harry Klee of the University of Florida studies a mutant form of tomato called "never-ripe" that has showed a dramatic delay in fruit ripening. Klee recently used the ETR1 gene sequences from Arabidopsis to discover similar genes in tomato plants. The DNA sequence of the "never-ripe" gene from these tomatoes is strikingly similar to that of the Arabidopsis ETR1 gene, says Bleecker.
This new understanding of how ethylene works will allow botanists to regulate developmental processes in many plants, Schaller and Bleecker believe. For example, mutant forms of ETR1 and "never-ripe" are what geneticists call dominant. When mutant forms of the gene are transferred into plants with normal genes, the mutant form overrides the normal form, resulting in a reduction or elimination of ethylene responsiveness. This process may soon be used to keep cut flowers fresh longer -- and extend the life of those veggies currently moldering away in your refrigerator bin.
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