German scientists have produced a "safer" genetically modified tomato with functional food benefits, the BBC reported this week. According to the report, scientists have not only managed to engineer a tomato plant that prevents its new genes from passing to other crops - an ongoing concern for organic farmers and conservation groups - but that also has much higher levels of a desired health-giving protein in the edible tissues of the plant. 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. Bock and colleagues built 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. 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. Commenting on the potential nutraceutical benefits of the tomatoes the scientists said: "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." Full findings are published in the September 2001 issue of Nature Biotechnology.