基于组织退化发育模型的家蚕丝腺高效丝蛋白质分泌功能的转化调控机制研究

Bombyx mori is a domesticated economic insect. The silk gland is the major reason why people domesticate, which is known as a specialized tissue with the strongest protein secreting capacity among insects. Improving protein fiber composition synthesized by silk gland and taking use of silk gland to produce exogenous protein efficiently are the major issue in sericulture and insect bio-engineering field. According to the preliminary work, we have found that: (1) Degenerated cells in silk gland which stop producing silk protein at the pupation stage, efficiently produce 30K protein. (2) With transgenic technology, we can make Posterior silk gland (PSG) express middle silk gland (MSG) specific protein SER3, and interesting changes of the molecular aggregation are found in the silk fibroin. The research is going to investigate the regulatory mechanism that up-regulate expressed protein in degenerated silk gland, such as 30Kc19 and other non-silk proteins, based on building various degeneration developmental models of silk gland which can be induced by hormone, drug and transgenic Hpgs gene. Further investigation is going to discuss the secretion regulation mechanism of heterogenous sericin protein SER3 in PSG based on transgenic silkworm. Eventually we aim to clarify the regulatory mechanism which makes silk gland efficiently express other protein, and lay a foundation to exploite new type of silk protein and cultivate high-efficiency expression strains for exogenous protein in silkworm.

家蚕丝腺是组织特化的、已知蛋白质分泌能力最强大的昆虫器官，是人类驯化和选择家蚕的主要对象。改良丝腺合成的蛋白质纤维成分和有效利用丝腺的高效蛋白质分泌能力生产外源蛋白，是养蚕业和昆虫生物工程领域世界瞩目的重大课题。 我们在前期工作发现：（1）停止丝蛋白合成的幼虫蛹化过程中的退化丝腺细胞，发生了高效合成30K非丝成分的储存蛋白质；（2）后部丝腺（PSG）表达中部丝腺（MSG）特异的SER3转基因家蚕，其丝素蛋白质出现了非常有趣的分子聚合变化。 本项目以建立的20E等诱导的、转Hpgs基因诱发的不同丝腺退化发育模型，探讨退化丝腺细胞中30K c19等非丝储存蛋白质的上调表达分泌调控机制；进一步以转基因蚕为材料，探讨PSG表达组织部位异源的SER3丝胶蛋白分泌调控机制。以期阐明丝腺细胞中高效的丝蛋白质合成功能转化为合成其它蛋白质的调控机制，为开发新型蚕丝蛋白和丝腺高效表达外源蛋白的家蚕积累基础。

项目背景：家蚕丝腺是高度特化的专一合成和分泌丝蛋白质的器官，是人类驯化和选择家蚕的靶标。家蚕丝腺的蛋白质合成与分泌功能决定了蚕茧的产量和质量，改良丝腺合成的蛋白质纤维成分是养蚕业世界瞩目的重大课题。另一方面，利用家蚕丝腺中蛋白质高效分泌功能的转化调控是家蚕新用途开发的重要基础。.主要研究内容：建立家蚕退化丝腺发育模型，研究退化丝腺中主要分泌蛋白质的变化，阐明丝腺细胞中合成和分泌“组织异源”蛋白质的调控机制。.重要结果及其科学意义：（1）建立了4种家蚕丝腺退化发育模型，阐明了丝蛋白专一性合成细胞转化为合成生殖等相关30K蛋白质的调控机制，发现了丝腺细胞能够在发育过程中自然转化和人工调节转化为高效合成其它蛋白质的直接证据，为开发应用丝腺高效生物反应器提供了新思路。（2）利用丝蛋白的氨基酸偏好性设计合成了研究家蚕丝腺氨基酸转运的标记载体，实现了丝腺靶向高效转移的量子点组织标记。（3）创制了转基因家蚕丝腺发育模型，发现降低后部丝腺特异的丝素基因表达能够显著提高外源重组蛋白的表达量，为突破家蚕丝腺生产外源蛋白效率低下的技术瓶颈发现了一个切入点。（4）创制了发育正常、能够高效生产新功能丝蛋白纤维的转基因家蚕新资源，培育出实用性家蚕新品系。突变体家蚕能够在后部丝腺高效合成和分泌亲水性丝胶蛋白Ser3，并且在体内自然掺入丝素蛋白质。从理论和实践两个层次证明了家蚕幼虫丝腺能够高效表达和分泌重组蛋白。