Custom-designed, mass silk production in genetically engineered silkworms

Area of Science:

• Biotechnology
• Materials Science
• Genetics

Background:

• Genetically engineered silkworms are crucial for producing silk with enhanced properties, particularly through the integration of spider silk genes.
• Existing transformation strategies face challenges with large DNA fragment integration and efficiency.

Purpose of the Study:

• To develop and evaluate novel transformation strategies for genetically engineered silkworms to produce superior silk proteins.
• To assess the impact of exogenous silk proteins on the mechanical and structural properties of engineered silk fibers.

Main Methods:

• Three distinct transformation strategies were employed: TALEN-mediated fibroin light chain fusion (BmFibL-F), TALEN-mediated fibroin heavy chain replacement (BmFibH-R), and transposon-mediated transformation (BmFibH-T).
• Exogenous silk proteins, including major ampullate spidroin 2 (MaSp2) and Eumeta variegate fibroin heavy chain (EvFibH), were introduced into silkworms.
• Silk fiber properties were analyzed for toughness, crystallinity, and gene expression changes via RNA-seq.

Main Results:

• The BmFibH-R strategy achieved high yields of exogenous silk proteins (51.02% MaSp2, 64.13% EvFibH) in cocoon shells.
• Engineered silk fibers exhibited significantly enhanced toughness (∼86% in BmFibH-T, ∼80% in BmFibH-R) and increased crystallinity (∼40%).
• The BmFibH-R system demonstrated minimal impact on endogenous gene expression.

Conclusions:

• Novel genetic engineering strategies, particularly BmFibH-R, enable efficient production of high-performance silk proteins in silkworms.
• The incorporation of exogenous silk proteins substantially improves silk fiber toughness and crystallinity.
• Genetically engineered silkworms serve as effective bioreactors for custom silk production, offering a promising avenue for advanced biomaterials.