In the March 1 issue of Genes & Development, Hajime Mori and colleagues at the Kyoto Institute of Technology in Kyoto, Japan report that they have developed a technique to produce genetically altered, green fluorescent silk fibers that are spun by the silkworm. The development of an insect system to produce foreign proteins has significant potential applications for silk or other economically important proteins.
Silkworms, or more precisely, the larvae of the moth Bombyx mori, spin silk to form a cocoon in which they will develop into moths. Mori's group took an approach in which they infected the silkworm larvae with a genetically engineered insect virus that carried an altered version of a silk protein. They fused the gene encoding the light chain of the fibroin protein -- a major protein component of silk -- to the gene encoding the green fluorescent protein from jellyfish. After the virus infects the larval cells, the virus embeds itself into the silkworm's DNA. Through a process called homologous recombination, the silkworm's natural fibroin gene was replaced with the new altered version. Remarkably, when ultraviolet light is shone on the silk glands of these invected larvae, the glands glow with an eerie green color! The development of this technique opens the door for genetic researchers to engineer silk proteins and reintroduce them into moths that can, in turn, produce genetically altered silk. This approach also has potential economic applications.
Theoretically, such a protein-producing insect could be used to produce important proteins, such as the spider silk protein spidroin, which has potential industrial uses ranging from the fibers in bullet-proof vests to parachutes.
This work was supported by Enhancement of Center of Excellence Special Coordination Funds for Promoting Science and Technology, Science and Technology Agency, Japan.The first author Masafumi Yamao was supported by the Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists.
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The reference for the paper is: Masafumi Yamao, Nagakuzu Katayama, Hiroshi Nakazawa, Minoru Yamakawa, Yoshiyuki Hayashi, Saburo Hara, Kaeko Kamei, and Hajime Mori. Gene targeting in the silkworm by use of a baculovirus. Genes & Dev. 13: 511-516.
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