An apple a day is supposed to keep the doctor away, and in the near future it might also help keep you out of the dentist's chair. Researchers at the International Horticultural Research Institute and Guy's Hospital in London are attempting to engineer genetically an apple that offers complete protection from tooth decay. In London yesterday, Prof David James of the institute described the work, which involves a peptide substance that could prevent decay-causing bacteria from sticking to the teeth, during a session of the British Association's annual Festival of Science.
Causing decided discomfiture in his audience, Prof James said there were upwards of 200 bacteria, numerous fungi and protozoas that enjoyed free room and board in our mouths, but only one - streptoccus mutans - caused decay.
The peptide, created by Dr Charles Kelly of the immunology department at Guy's, was shown to block the bacterium for up to 80 days when used on human volunteers. The peptide occupies the "receptor site" where the bacterium adheres to the teeth before beginning its dirty work. The peptide gets there first, leaving the bacterium nowhere to go.
Prof James is now trying to engineer this peptide into an apple, although the peptide could be administered in a mouthwash or by another method.
"Our idea in the longer term is to have a method of delivering it with a natural product," he said. "Part of the strategy is we want to encourage healthy eating." Much additional work was needed, however. How much of the peptide is required to do the job is not yet known, nor is it known whether an apple can be produced with enough peptide to be beneficial.
Such an apple would also have to go through the testing applied to any pharmaceutical product, he added, a process that could take five to seven years. Prof James described other genetic modification work which involved engineering genes into fruit. Among the projects cited was an attempt to improve apple storage, an attempt to reduce the size of fruit trees to make them easier to manage, and an attempt to engineer gray mould disease resistance into strawberries. Strawberry growers around the world knew and hated this disease, Prof James said, and breeders were "at a dead end" using conventional methods. An anti-fungal protein had been identified in pears, however, and this has been transferred into strawberries. So far two clones seem to have taken it up, and these are now strongly resistant to gray mould.
