A null mutant of the Streptomyces virginiae barA gene encoding a butyrolactone autoregulator receptor and its phenotypic and transcriptional analysis

The Streptomyces virginiae barA gene encodes a specific receptor protein fo r virginiae butanolide (VB), one of the gamma-butyrolactone autoregulators of Streptomyces species. By homologous recombination, a barA null strain wa s constructed to clarify the in vivo function of BarA protein in S. virgini ae. The Delta barA mutant showed no difference in terms of growth, but lost VB production and produced virginiamycin 7h earlier than the wild-type str ain. These results indicated that, phenotypically, BarA protein acts negati vely in virginiamycin biosynthesis and positively in VB biosynthesis. Furth ermore, Northern (RNA) blot analysis of the Delta barA mutant revealed that transcription of the BarA target gene (barB) was derepressed, confirming t hat BarA acts as a transcriptional repressor in S. virginiae.