17.11.95

Race to reach the market

THE non-squashy tomato was genetically engineered in the laboratory of Don Grierson, 
professor of plant physiology at Nottingham University. In processed forms, such as sauce 
or pastes, it is likely to reach the market in the next year or two in America, and later in Britain.

Because of the tight regulations governing biotechnology, Prof. Grierson needs special 
permission to eat one of his own tomatoes at present - since this could count as dispersal 
into the environment.

Working with the biotechnology company Zeneca, Prof. Grierson found a way to prevent 
tomatoes becoming squashy by implanting an artificial gene that blocks the action of an 
enzyme involved in the ripening process. The gene does not come from any other creature 
but is custom made in his laboratory to block the enzyme - called polygalacturonase - which 
breaks down pectin in the cell walls of tomatoes and makes them soft.

Antisense genes are identical to natural ones that manufacture important bio-chemicals - but 
the information in them reads back to front.

To make the enzyme, the tomato uses a material called messenger RNA. Prof. Grierson's 
gene produces "antisense RNA" that becomes entangled with the sense RNA, preventing 
the manufacture of polygalacturonase - a feat that has applications for many fruits, vegetables and flowers.

Calgene, a Californian biotech company, has extended this work. Using the same technique, 
it has produced tomatoes that not only stay firmer but also taste better because growers allow 
them to ripen on the plant. Its "Flavr Savr" tomatoes will probably beat Zeneca's on to the market.