The molecular breeding of the silkworm which make silk protein of different insect and the production of new fiber.

本研究的目的是利用基因工程技术培育不同昆虫品种的蚕丝，构建高效的家蚕育种体系。在最初的两年里，我们试图用一种不会杀死家蚕的杆状病毒作为转移载体来创造出能吐丝的家蚕。然而，尽管我们已经用许多家蚕进行了实验，但我们不能用这种方法制造出转基因家蚕。然后，利用DNA型转座子--PiggyBac系统，进行了蜘蛛丝基因鞭毛状丝基因对家蚕染色体DNA的种系转移实验。鞭毛状丝具有较高的伸长率，伸长可达3倍。因为蜘蛛是吃肉的，所以大规模繁殖很困难。一只蜘蛛吐丝好几种。蜘蛛很难只纺出鞭毛状的丝。然后我们认为，制造一种产生鞭毛状丝质的蚕丝是有意义的。我们将含有鞭毛状丝蛋白基因的不完全的iggyBac基因导入家蚕基因组DNA中，证实表达的鞭毛状丝蛋白存在于蚕茧中。转化到家蚕基因组DNA中的鞭毛状丝蛋白基因能够稳定地保持。然而，重组家蚕生产的蚕茧中鞭毛状丝蛋白的含量仅占总蚕茧蛋白质量的1%~2%。一个即将到来的主题是提高蚕丝的比例。

The purpose of this study is to breed silkworms which spin silk of different insect species by genetic engineering and to construct system of more efficient breeding. For first two years, we have tried to creat the silkworm which spin spider silk using a baculovirus which does not kill silkworms as a transfer vector. However, we can make no transgenic silkworm by this method though we have experimented using many silkworms. Then, using system of piggyBac which was a DNA type transposon, we have done the germline transfer experiment of a gene of the spider silk, flagelliform silk, to chromosome DNA of silkworm. The flagelliform silk has a high stretchiness, and expands to the length of 3 times. Because a spider is eating meat, the mass breeding is difficult. A spider spins several kinds of silk. It is difficult for the spider to spin only the flagelliform silk. Then we thought that it is significant to make a silkworm which produces flagelliform silk. We have transferred the incomplete piggyBac, in which flagelliform silk gene was incorporated, into genome DNA of a silkworm, and we confirmed that the expressed flagelliform silk protein was included in a cocoon. The flagelliform silk gene which transferred into genome DNA of a silkworm can be maintained stably. However, the content of flagelliform silk protein in a cocoon made by the recombinant silkworm was only one or two% of total cocoon protein mass. a coming theme is to raise the ratio of the spider thread which the silkworm makes.