The silk worm in normal light

Professor Hajime Mori, at the Kyoto Institute of Technology, told BBC News Online: "Our work has significant economic potential in improving silk, which is of particular interest in Kyoto, the traditional home of the kimono."

However, this is not because bright new colours are likely to take the world of kimono fashion by storm. Professor Mori explains that the fluorescence gene would act as a marker of success.

The silk worm under fluorescent conditions

If a desirable gene, say for greater strength, was successfully inserted into the silk worm, it would replace the fluorescence gene. The absence of the green colour would show the process had been successful.

Industrial uses

Other commercial uses could exploit the newly-created ability of the silkworm to produce "foreign" proteins. The spider silk protein, spidroin, could be grown and harvested with relative ease. It has potential industrial uses ranging from bullet-proof vests to parachutes.

The view of silk glands from normal (left) and genetically engineered silk worms

Professor Mori's team used an insect virus to insert a jellyfish gene for fluorescence into female moths. These then mated with normal male moths.

Around three per cent of larvae subsequently born produced glow-in-the-dark silk fibres. Two more generations of larvae were bred from these and the fluorescent gene was passed down.