Regulatory Mechanism About Protein Synthesis And Secretion Efficiency In Posterior Silk Gland Based On Transgenic Silkworm SER(Ser3/Ser3)and TBH(Hpl/Hpl)

The silk gland of the silkworm is the target tissue for domestication and animal husbandry of silkworms.It possesses the most powerful synthetic and secreted protein function of the known insects.The silk gland bioreactor is also widely expected by the industry.However,the efficiency of expressing exogenous proteins is far lower than endogenous silk protein,and silk glands dysplasia is general among transgenic silkworm.Using the piggyBac transposon,the laboratory obtained two transgenic silkworms,SER and TBH,which efficiently express sericin(Ser3)and silk fibroin heavy chain-like protein(Hpl)in the posterior silk gland.Posterior silk gland of SER is normal development and posterior silk gland of TBH is abnormal development.In this paper,we compared the differential mechanism of the development of posterior silk gland between SER and TBH silkworm through the study of silk gland tissue development,cell structure,and molecular signaling pathways of protein synthesis and secretion regulation.The main results are as follows:TBH and SER silkworm posterior silk gland cells can synthesize Hpl or Ser3 proteins efficiently,respectively.Ser3 protein can be secreted from glandular cells to glandular lumen without any obstacles,and has no statistical significance on nuclear replication and growth of silk gland.The nucleus DNA replication rate of the posterior silk gland of TBH silkworm decreased,and the growth of the posterior silk gland was significantly inhibited.The secretion of protein synthesized by the posterior silk gland of TBH silkworm to glandular lumen was significantly reduced.A large number of protein vesicles were accumulated in the cells.The structure of endoplasmic reticulum and Golgi body gradually disappeared,and the apoptotic level of autophagy was induced to rise.Further phosphorylated proteomic analysis showed that,compared with wild type,the differentially expressed phosphorylated proteins in the posterior silk gland cells of TBH silkworm were mainly related to protein misfolding in endoplasmic reticulum.Proteins phosphorylation of the ER associated protein degradation and the endoplasmic reticulum stress response are changed significantly.It is suggested that the protein synthesized in the silk gland cells of TBH may not be correctly folded which leads to protein accumulation in cells,and feedback inhibits the growth of silk gland cells.