Drugs on tap from morning dew
THE "sweat" of plants could in future yield a rich harvest of drugs and chemicals. That is the hope of researchers who have created tobacco plants that ooze foreign proteins from their leaves each morning.
Plants can be engineered to produce everything from vaccines to plastics. But extracting proteins from plant tissue is often complicated and expensive. Instead, Ilya Raskin and his colleagues at Rutgers University in New Jersey wondered if plants could excrete proteins in the "dew drops" found on leaves.
During the night, when leaves lose less moisture by evaporation, pressure builds up inside and squeezes fluid out-a process called guttation. This fluid contains small amounts of protein, which Raskin guessed must come from the fluid in the spaces between cells. So Raskin and his team genetically engineered tobacco plants to produce three foreign proteins in this intercellular fluid, including the green fluorescent protein from jellyfish.
Just as they hoped, the foreign proteins showed up in the dew on the leaves. In the future, the technique might be applied to other plants that produce large drops of guttation fluid, such as tomatoes and grasses. The drops could be sucked or shaken off the leaves each morning and processed to purify the proteins (Plant Physiology, vol 124, p 927).
"It would provide a system for obtaining fluid that is already purified and concentrated," says Hugh Mason of Cornell University in New York, who works on vaccine expression in potatoes. The amount of protein Raskin's team has been able to get expressed-about 2.8 per cent of all the protein in the guttation fluid-is comparable to what other people have been able to extract from the plant itself, says Mason.
Raskin thinks the method could be used in combination with another approach he has pioneered for making plants release proteins from their roots (New Scientist, 1 July, p 27).
Author: Nell Boyce, Washington DC
New Scientist issue: 25th November 2000
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