Deciphering the Regulon of Streptomyces coelicolor AbrC3, a Positive Response Regulator of Antibiotic Production
ABSTRACTThe atypical two-component system (TCS) AbrC1/C2/C3 (encoded bySCO4598,SCO4597, andSCO4596), comprising two histidine kinases (HKs) and a response regulator (RR), is crucial for antibiotic production inStreptomyces coelicolorand for morphological differentiation under certain nutritional conditions. In this study, we demonstrate that deletion of the RR-encoding gene,abrC3(SCO4596), results in a dramatic decrease in actinorhodin (ACT) and undecylprodiginine (RED) production and delays morphological development. In contrast, the overexpression ofabrC3in the parent strain leads to a 33% increase in ACT production in liquid medium. Transcriptomic analysis and chromatin immunoprecipitation with microarray technology (ChIP-chip) analysis of the ΔabrC3mutant and the parent strain revealed that AbrC3 directly controls ACT production by binding to theactII-ORF4promoter region; this was independently verified byin vitroDNA-binding assays. This binding is dependent on the sequence 5′-GAASGSGRMS-3′. In contrast, the regulation of RED production is not due to direct binding of AbrC3 to either theredZorredDpromoter region. This study also revealed other members of the AbrC3 regulon: AbrC3 is a positive autoregulator which also binds to the promoter regions ofSCO0736,bdtA(SCO3328),absR1(SCO6992), andSCO6809. The direct targets share the 10-base consensus binding sequence and may be responsible for some of the phenotypes of the ΔabrC3mutant. The identification of the AbrC3 regulon as part of the complex regulatory network governing antibiotic production widens our knowledge regarding TCS involvement in control of antibiotic synthesis and may contribute to the rational design of new hyperproducer host strains through genetic manipulation of such systems.