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Thursday, 30 August, 2001, 21:20 GMT 22:20 UK
GM tomatoes 'offer health boost'
Bock AP
Ralph Bock: Hopes to make tomato plants that express vaccines
By BBC News Online's Jonathan Amos

German scientists have produced a "safer" genetically modified tomato, which they believe could lead to a range of fruits and vegetables that give a health boost to anyone who eats them.

This system paves the way to efficient production of edible vaccines, pharmaceuticals, and antibodies in tomato

German research team
The tomato plant has been engineered in a way that prevents its new genes from passing to other crops - something which has been a major concern for organic farmers and conservation groups.

New laboratory techniques also mean much higher levels of a desired health-giving protein appear in the edible tissues of the plant - the bright red fruits themselves.

The scientists envision "super tomatoes" that offer consumers substantially increased vitamin content. "We are also planning to make tomato plants that express vaccines in the fruits for oral immunisation," lead researcher Professor Ralph Bock, at the Institute of Plant Biochemistry and Biotechnology in Munster, told BBC News Online.

Non-leafy tissues

The work of Bock and colleagues builds on a newly developed technique for the genetic modification of plants.

Instead of introducing a gene for a particular trait into a plant's nuclear DNA, the coding sequence is put in amongst the small amount of DNA found in small cellular compartments known as plastids. In this case, the German team targeted chloroplasts, which generate energy from sunlight.

Tomato Bock
Future food: Regenerating tomatoes in the lab
Crucially, the DNA in chloroplasts, unlike nuclear DNA, is not transmitted in pollen. So this eliminates the possibility that the modified plant's genetic material might "contaminate" other crops or pass undesirable traits to weeds.

Until now, though, chloroplast transformation has been achieved routinely only in tobacco; other plants have been sterile or shown disappointing results in the non-leafy tissues, such the fruits.

'New applications'

"Tobacco is a good model for basic science but for applied biotechnology you need a food plant," Professor Bock said.

"That's why we've focused on tomatoes. To make it work, we've had to solve a number of technical difficulties - mostly related to plant tissue culture and regeneration. You need to optimise a lot of parameters in these areas such as nutrients, plant hormones and light intensity."

"And in our case we got really good expression in the tomato fruit, which opens up a lot of new applications."

So far, the German team has used only a marker gene in its experiments - to prove the approach works. More useful genes will now be incorporated into the tomatoes.

Tomato Bock
Tomato seedlings: The maker gene means modified plants will stay green when exposed to an antibiotic
The team reports its work in the journal Nature Biotechnology.

The scientists write: "Given the generally very high foreign protein accumulation rates that can be achieved in transgenic chloroplasts, this system paves the way to efficient production of edible vaccines, pharmaceuticals, and antibodies in tomato."

And in an accompanying article, a US expert agreed that GM tomatoes with transformed plastids could make it easier to develop edible vaccines.

Pal Maliga, from Rutgers University in Piscataway, New Jersey, writes: "The report of plastid transformation in tomato is... a milestone achievement, and the capacity to express foreign proteins at a high level in consumable fruit should open new opportunities for engineering the next generation of medicinal products that are more palatable to the consumer."

A number of research groups are now looking to produce food crops that have enhanced nutritional or medicinal value. These new foods are sometimes referred to as nutraceuticals.

See also:

09 Aug 01 | Sci/Tech
Weeds 'can inherit long-lived genes'
01 Mar 00 | Sci/Tech
Plants produce human protein
19 May 99 | Sci/Tech
Modified genes that stay put
13 Oct 00 | Sci/Tech
Plant barrier to 'jumping genes'
20 May 99 | Sci/Tech
GM pollen 'can kill butterflies'
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