Expression of an antimicrobial peptide persulcatusin fused with calmodulin in rice cultured cells

Antimicrobial proteins and peptides are potential alternatives to antibiotics. Persulcatusin is an antimicrobial peptide found in the taiga tick Ixodes persulcatus. We constructed fusion genes that encode, from the N-terminus to the C-terminus, a signal sequence of rice α-amylase 3D, mouse calmodulin, a target sequence of TEV protease of tobacco etch virus, and persulcatusin with or without a His tag at the N-terminus of the mature fusion protein. These fusion genes were then introduced into rice. Western blot analysis detected persulcatusin fusion proteins in transgenic calli, suspension cells, and their culture medium. Antimicrobial activity against Staphylococcus aureus was detected in the protein extracts prepared from the transgenic callus but not from the non-transgenic wild-type callus, and TEV protease treatment to release persulcatusin from the fusion protein enhanced antimicrobial activity. The growth of the transgenic rice plants was unaffected. Our results indicate that functional persulcatusin can be produced in rice cells. This provides a basis for the mass production of persulcatusin for therapeutic use against bacterial infectious diseases in humans and livestock.