杏吧原创

BY BLOCKING production of a natural chemical, genetic engineers have created
tobacco plants that are super-resistant to aphids. A related approach could one
day persuade plants to produce valuable compounds such as fragrances and drugs,
the researchers say.

Many flowering plants have tiny glands called trichomes that secrete
substances onto leaf surfaces. George Wagner and his colleagues at the
University of Kentucky in Lexington tinkered with an enzyme in tobacco trichomes
that completes the production of an aphid-repelling substance called
cembratriene-diol. Strangely, the diterpene precursor from which this repellent
is made is even more potent, which is why Wagner wanted to halt the trichomes鈥�
production process at this point.

When Wagner blocked production of the enzyme, the tobacco plants produced 20
times as much of the diterpene as normal. 鈥淭he modified plants were
significantly less colonised by aphids,鈥� says Wagner.

He says the ultimate goal is to use trichomes as chemical factories. 鈥淲e hope
to trick the trichomes into making valuable compounds,鈥� he says.

Bill Cockburn of the University of Leicester says trichomes can produce huge
amounts of chemicals, up to 30 per cent of the weight of a dried-out leaf.
鈥淎lso, the trichome is a non-essential part of the plant, so you could mess
around with it without disturbing the rest of the plant,鈥� says Cockburn.

Substances produced by trichomes include the antimalarial drug artemisinin
and the antidepressant hypericin. Aromatic plants such as mint, oregano and hops
owe their unique fragrance and spiciness to substances produced by trichomes.
Ultimately, Wagner and his colleagues hope to be able to insert genes that code
for substances not made naturally in the trichome.