The group of Hidetoshi TERAMOTO et al. developed a bacterial system to screen for B. mori phenylalanyl-tRNA synthetases with altered amino-acid specificity. They created transgenic B. mori lines expressing the selected synthetase variants in silk glands, and found that some of them supported the efficient in vivo incorporation of azidophenylalanine into silk fiber. The obtained silk was bio-orthogonally reactive with fluorescent molecules, using „click chemistry“. It was also possible to largely reduce the amount of expensive non-natural amino acids in silkworm feed about 30 fold, and, according to the authors, „activated silk can be produced with a cost increase of about 10 to 50% .