Overexpression of Gloverin2 in the Bombyx mori silk gland enhances cocoon/silk antimicrobial activity.

The Bombyx mori cocoon/silk possesses many immune-related components, including protease inhibitors, seroins, and antimicrobial peptides, which likely help to protect the pupating larva from infection. However, the natural antimicrobial activity of the B. mori cocoon/silk is still too weak for biomedical applications. With the goal of enhancing this natural activity, we constructed a transgenic vector to overexpress the B. mori antimicrobial peptide Gloverin2 (BmGlv2) under control of the silk gland-specific Serion1 promoter. Transgenic silkworms were generated via embryo microinjection. A low level of BmGlv2 was expressed in the non-transgenic silk gland, but BmGlv2 was efficiently overexpressed and proteolytically activated in the transgenic line. Overexpressed BmGlv2 was secreted and incorporated into the silk during spanning without affecting cocoon/silk formation. Moreover, the transgenic cocoon/silk had significantly greater inhibitory activity against bacteria and fungi than the non-transgenic cocoon/silk. This strategy could help enhance the antimicrobial performance and biomedical application of silk.