家蚕丝蛋白合成的代谢调控研究

As a holometabolous insect, silkworm spins cocoon after the last instar. After spinning, the larva metamorphoses into a pupa and then into a moth. In the silk industry, the cocoon shell rate was used to represent the efficiency of the silk synthesis, which is the percentage of cocoon shell weight in the total weight of the cocoon and pupa. As a key economic character, the cocoon shell rate has an important influence on the sericulture income, and even on the productivity of the whole silk industry. The cocoon shell rate increases through the breeding program, but it is difficult to break 25%. Our preliminary study implied the mutual competition between the silk gland and fat body for the nutrient distribution in the silkworm, which showed great effect on the efficiency of the silk synthesis. Our study also suggested that the metabolism of glycine played an important role for regulating the competition. Artificial addition of glycine could greatly improve the cocoon shell rate. To further elucidate the mechanism and establish the gene regulation means of the key amino acids. This project intends to use a series of technology, including transgene, gene interference and gene editing, which have been built in our lab for many years. This project will mainly research on the regulatory pathway of amino acid metabolism, and investigate its influence mechanism on the efficiency of silk synthesis, and regulate key target by genetic manipulation in hope of creating new genetic material with high efficient of silk synthesis, which will provide basic support for cultivating strains with high silk yield.

家蚕作为完全变态昆虫，在其末龄幼虫结束后吐丝结茧，并经蛹期羽化为成虫。产业应用中通常以茧层重占蚕茧总重量的百分比，即茧层率来表示蚕丝的合成效率。作为关键经济性状，茧层率的高低，对养蚕收入甚至整个行业的生产效率都有重要的影响。通过育种手段，茧层率得到不断提高，但达到目前的25%左右之后，再难获得新的突破。本团队前期研究表明，家蚕丝腺与脂肪体在营养分配中存在竞争关系，并极大的影响了蚕丝的合成效率。研究还发现，甘氨酸等代谢水平，在调节这个竞争关系中扮演了重要角色，人为添加甘氨酸，可以较大幅度提高茧层率。为深入阐明机理并建立关键氨基酸代谢的基因调控手段，本项目拟利用本实验室成熟转基因技术、基因功能干扰技术和基因编辑技术，重点研究主要氨基酸代谢调控通路，探索其对蚕丝合成效率的影响机制，并通过关键调控靶标的遗传操作，创制高效合成蚕丝的新型遗传素材，为高产丝量品种的育成提供基础支撑。

家蚕作为完全变态昆虫，在其末龄幼虫结束后吐丝结茧，并经蛹期羽化为成虫。产业应用中通常以茧层重占蚕茧总重量的百分比，即茧层率来表示蚕丝的合成效率。作为关键经济性状，茧层率的高低，对养蚕收入甚至整个行业的生产效率都有重要的影响。通过育种手段，茧层率得到不断提高，但达到目前的25%左右之后，再难获得新的突破。鉴于此，本研究采用生物信息学和分子生物学中的多种技术手段，在蛋白质翻译过程，研究丝蛋白合成所需要主要氨基酸（甘氨酸）、氨基酸转运蛋白和mTORC1信号通路对丝蛋白合成效率的影响。利用遗传操作改变丝腺中氨基酸（甘氨酸）的水平以及调节mTORC1信号的激活，增加了丝蛋白合成的效率，获得了三个吐丝量和茧层率显著提高的转基因家蚕品系。此外，利用转基因技术和CRISPR/Cas9基因编辑技术，证明BmSLC7A5通过调节5龄期丝腺中的亮氨酸含量，调控mTORC1信号的激活，从而控制丝蛋白及相关转录因子的合成。本文从蛋白质翻译水平，证明了丝蛋白合成所需的主要氨基酸以及mTORC1信号通路能够参与调节丝蛋白合成的效率。本项目共发表论文27篇，其中SCI论文26篇，专利授权1项。此外，从营养信号的角度初步解析了5龄期家蚕丝蛋白大量合成的分子机制，为增加蚕丝产量提供了新的方向和思路.