National

SERICULTURE GENE MODIFICATION

Biotechnologists turning to silkworms

by Hiroshi Yamada

Kyodo News

The ancient technology of producing raw silk is now being applied by such state-of-the-art industries as genetic engineering and biotechnology.

Sericulture, a technology thought to have been introduced to Japan in the Yayoi Period (300 B.C. to A.D. 250) from China, played a key role in modernizing the country during and after the Meiji Era (1868-1912).

While the development of artificial fibers and rayon dealt the silk industry a severe blow, the National Institute of Agrobiological Sciences in Tsukuba, Ibaraki Prefecture, is now breeding genetically modified silkworms that produce proteins instead of silk.

Toray Industries Inc., whose line of business includes fibers, pharmaceuticals and medical equipment, operates what it calls an “insect factory” in Ehime Prefecture. The factory turns out interferon, which is used to treat cats and dogs with viral infections.

Visitors to the NIAS laboratory in Tsukuba can see genetically modified silkworms that feature the fluorescent genes of jellyfish and coral.

When light is focused on these creatures, their heads shift right and left while the glow of their eyes changes subtly.

“Aren’t they cute?” asked 55-year-old Toshiki Tamura, who heads a team in the NIAS Insect Biotechnology and Sericology Department.

The team’s goal is to breed genetically modified silkworms that produce useful proteins. The group has already succeeded in turning out genetically modified “shining bright cocoons.”

“What we have to do from this point is decide what sort of genes we should incorporate into them,” Tamura said.

The team is taking steps to launch the production and commercialization of substances such as collagen and interferon, which genetic engineering has thus far been unable to address.

“If we stop, we are going to be left behind,” he said, voicing confidence that Toray will remain a world leader in this arena.

Toray’s “insect factory” operates under strict controls.

Before visitors are taken to the breeding room, they must remove their shoes, change into lab uniforms and put on caps and sterilized boots.

Silkworms injected with a genetically altered virus are placed side by side on shelves, where they produce interferon.

They are kept there to breed the virus within their bodies so that interferon can be extracted from their body fluids.

Yoshizumi Ueda, chief of the animal medicine office, said the room is known as the insect factory because the silkworms themselves are production facilities.

According to Ueda, sales of medicine used to treat cats and dogs suffering from infectious diseases amounts to about 1 billion yen a year at home and in Europe.

Japan has towered over other countries in terms of its silkworm-breeding skills.

Experts say Japan’s original artificial animal feed is symbolic of its advanced breeding technology.

The feed, which is solid like sweet bean jelly, is made up of beans, agar and mulberry leaves.

More than 1,000 different types of silkworms are reportedly bred throughout the world, with Japan breeding more than 600 kinds. It also leads the world in terms of decoding the silkworm genome.

Having been domesticated for so long, silkworms are well-suited to genetic engineering initiatives.

“Silkworms cannot fly even when they become moths,” said Tamura of NIAS. “We don’t have to worry about their entering the realm of nature even after they are genetically modified. They can be contained easily.”

Their production efficiency is also excellent, observed Toray’s Ueda.

Although silkworms are believed to have originated in China, Japan’s sericulture technology grew sophisticated during the Edo Period (1603-1967), to the extent that France and Italy — advanced nations in the cultivation of silkworms at the time — focused their attention on this country.

The silkworm memorial hall in Oya, Hyogo Prefecture, keeps on display a three-volume confidential document on sericulture published by Uegaki Morikuni in 1803.

The document includes information on production, the source of different kinds of silkworms, their breeding habits and how to get threads from cocoons, according to Zenjiro Inoue, a sericulture researcher.

Philipp Franze von Siebold, who served as a doctor at the Dutch trade office in Nagasaki during the Edo Period, reportedly presented a set of these documents to a Dutch king.

European nations that were involved in breeding silkworms at that time suffered a blow when the creatures fell victim to disease.

Johann J. Hoffmann, a German scholar on Japan, joined others in translating the document, publishing it in France and Italy.

The preface in the French edition contains a passage stating that French farmers ought to copy Japanese methods with great care.

Inoue said Uegaki’s document was Japan’s “first technology export.”

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