Recent Development in the Use of Blasticidin S, a Microbial Fungicide, as a Useful Reagent in Molecular Biology

Blasticidin S (BS), a fungicide of microbial origin, is an inhibitor of protein synthesis in both prokaryotes and eukaryotes. As BS proved to exert a potent curative effect on rice blast disease, it has been widely used as a practical control agent in eastern Asia. Several BS-resistant microorganisms were found to produce BS deaminase (EC 3.5.4.23), which catalyzes the hydrolytic deamination of cytosine moiety in BS to give a nontoxic deaminohydroxy derivative. The isolation of thebsrgene from aBacillus cereus-resistant plasmid allowed establishment of a new transformation system using BS as a selective reagent in various organisms. Recently, another BS deaminase gene,bsd,has been cloned fromAspergillus terreusand its nucleotide sequence was determined. Unlikebsr, bsdpossessed no highly biased codon use and thus proved to be more suitable for heterologous expression in various organisms. Successful application of the BS–bsdtransformation system of eukaryotes, as well as some advantages over other systems, will be reviewed.