This invention relates to the fields of
synthetic biology and
metabolic engineering, specifically to a
Streptomyces promoter selection marker and its application. The selection
marker gene is *
Streptomyces lilacinus*.
Streptomyces lavendulae
Glutamine indigo synthase
gene derived from CGMCC 4.1386 idgS This invention screens endogenous promoters of *Streptomyces freundii* using heterologously expressed idgS genes; and constructs a detection
system for endogenous promoters of *Streptomyces freundii* using this scheme, which can rapidly detect endogenous promoters of *Streptomyces freundii* and the strength of each
promoter.