Glyphosate is a herbicide that kills plants by blocking the creation of an enzyme called EPSP synthase, which the plant needs to synthesise amino acids. But crops and weeds are killed by glyphosate Over the past few years, Monsanto liis marketed soya beans and cotton which have been engineered to resist glyphosate. But environmentalists are concerned that the resistance could spread to wild relatives of some crops, creating super weeds that would not be easy to control. The concern is greatest for cereal crops, which can interbreed with some grassy weeds. Henry Daniell and his colleagues at Auburn University in Auburn, Alabama, u tackled the problem by inserting the resistance gene, taken from a petunia, into the plant's choloroplasts.
Chloroplasts are the structures which manufacture chlorophyll.
They have their own genome, and the chloroplasts are passed down only through the female plant so that pollen cannot spread the resistance. Daniell constructed a resistance gene which would bind only to a piece of DNA in the chloroplasts, and used a gene gun to insert it. The altered chloroplasts manufactured large amounts of EPSP synthase, overwhelming the glyphosate's effect. If the technique can be applied to crops, it removes worries about crops interbreeding with weeds, and makes it easier for seed companies to win approval for the products. Ingo Potrykus, a plant developmental biologist at the Institute of Plant Sciences in Zurich, has his doubts.