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出能纺不同昆虫种类蚕丝的蚕，并建立更高效的育种体系。在最初的两年里，我们尝试用一种不会杀死蚕的杆状病毒作为转移载体来培育能吐丝的蚕。然而，尽管我们用许多家蚕进行了实验，却无法用这种方法获得转基因家蚕。然后，利用一种DNA型转座子piggyBac体系，将蛛丝（鞭毛丝）的一个基因转移到家蚕的染色体DNA上，进行了种系转移实验。鞭毛状蚕丝具有很高的拉伸性，可伸展至长度的3倍。因为蜘蛛是食肉动物，所以很难大规模繁殖。蜘蛛能纺好几种丝。蜘蛛很难只纺鞭毛状的丝。于是我们想到，培育一种产鞭毛丝的蚕是很有意义的。我们将含有鞭毛丝基因的不完整的piggyBac转移到家蚕的基因组DNA中，并证实表达的鞭毛丝蛋白包含在蚕茧中。将鞭毛丝基因转移到家蚕的基因组DNA中可以稳定地维持。而重组蚕茧中鞭毛状丝蛋白的含量仅占茧总蛋白的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.