Characterization of three positive regulators for tetramycin biosynthesis in Streptomyces ahygroscopicus

Three putative regulatory genes, namely, ttmRI , ttmRII , and ttmRIII , which are present in the tetramycin ( ttm ) biosynthetic gene cluster, were found in Streptomyces ahygroscopicus . Disruption of ttmRI , ttmRII , or ttmRIII reduced tetramycin production, and their complementation restored their production at varying degrees. Gene expression analysis of the wild-type (WT) and mutant strains through reverse transcriptase-polymerase chain reaction (RT-PCR) of the ttm gene cluster showed that the expression levels of most of the biosynthetic genes were reduced in Δ ttmRI , Δ ttmRII , and Δ ttmRIII . Electrophoretic mobility shift assays demonstrated that TtmRI, TtmRII, and TtmRIII bound the promoters of several genes in the ttm gene cluster. This study found that these three proteins are a group of positive regulators that activate the transcription of the ttm gene cluster in S. ahygroscopicus . In addition, the Δ ttmRII reduced the degree of grey pigmentation. Thus, TtmRII demonstrated a pleiotropic regulatory function on tetramycin biosynthetic pathway and on development.