Abstract

Spider dragline silk is a natural fiber that has excellent tensile properties; however, it is difficult to produce artificially as a long, strong fiber. Here, the spider (Araneus ventricosus) dragline protein gene was cloned and a transgenic silkworm was generated, that expressed the fusion protein of the fibroin heavy chain and spider dragline protein in cocoon silk. The spider silk protein content ranged from 0.37 to 0.61% w/w (1.4–2.4 mol%) native silkworm fibroin. Using a good silk-producing strain, C515, as the transgenic silkworm can make the raw silk from its cocoons for the first time. The tensile characteristics (toughness) of the raw silk improved by 53% after the introduction of spider dragline silk protein; the improvement depended on the quantity of the expressed spider dragline protein. To demonstrate the commercial feasibility for machine reeling, weaving, and sewing, we used the transgenic spider silk to weave a vest and scarf; this was the first application of spider silk fibers from transgenic silkworms.

Highlights

  • Orb-web spiders, such as Nephila and Araneus genera, produce a variety of silks that have excellent mechanical properties

  • In the case of dragline silk, partial cDNA sequences have been obtained from the major ampullate silk protein (MaSp) of Nephila clavipes (MaSp-1[2] and -2[3]) and Araneus diadematus (ADF3[4] and -4[4])

  • In 2007, we reported fibroin H-chain modification [26] and the development of transgenic silkworms that expressed spider (Araneus ventricosus) dragline proteins [20]

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Summary

Introduction

Orb-web spiders, such as Nephila and Araneus genera, produce a variety of silks that have excellent mechanical properties. Their dragline silks are among the strongest fibers, approximately threefold tougher than aramid fibers and fivefold stronger than steel [1]. The network structure of the dragline contains a low volume fraction of small crystals, separated by long amorphous domains. This complex structure is thought to be the origin of the incredible strength, toughness, and viscoelasticity of spider dragline silks [5]

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