The Study On SCO2120/SCO2121-a Novel Two-component Signal Transduction System In Streptomyces Coelicolor A3(2)

Streptomyces is a class of Gram-positive,soil-dwelling,and filamentous bacteria.They are well known for their remarkable ability to produce a vast array of secondary metabolites,including antibiotics,some antitumors and immunosurpressors.As the best representative of actinomycetes,the whole genome sequence of Streptomyces coelicolor A3(2)reveals numerous secondary metabolite biosynthetic gene clusters.The secondary metabolism,including the biosynthesis of secondary metabolite,are always regulated by Two-component Signal Transduction Systems.Typically,TCS comprise a membrane-bound histidine kinase that senses a specific environmental stimulus,and a cognate response regulator that mediate the cellular response,mostly through transcriptional regulation of target genes.In this study,we aimed at determining the function and the mechanism of the regulator in SCO2120/SCO2121,which is a novel two-component system(TCS)in Streptomyces coelicolor A3(2).Firstly,we constructed the in-frame deletion mutant of the RR-coding gene sco2120 after the construction of recombinant vector and the conjugation between Streptomyces coelicolor and E.Coli.After phenotype screening,we identified that the deletion of sco2120 led to impaired aerial hypha formation and sporulation,and drastically decreased actinorhodin(ACT),prodiginines(RED)and the calcium-dependent antibiotic(CDA)than M145 and the complemented strains(?2120/pSET2120,A2120/pSET2120-2121,?2120/pHLY2120,?2120/pMS2120-1,A2120/pMS2120-2).The results indicated that sco2120 is a global regulator in both morphological differentiation and antibiotic biosynthesis in S.coelicolor.In vitro binding assays showed that sco2120 activates ACT,RED and CDA production directly through the pathway-specific activator genes act?-ORF4,redZ and cdaR respectively.DNase I footprinting assays revealed that the DNA binding site for sco2120 might be the sequence 5'-CCGGCGCACCT-3',which need ChIP-seq for futher evidence to support.This study further reveals the complexity of TCSs in regulation of morphological differentiation and antibiotic biosynthesis in Streptomyces.