Mechanisms Of WblI In Regulating The Antibiotic Biosynthesis In Streptomyces Lividans

Regulators of the Whi B-like(wbl)family are playing important role in the complex regulation of metabolic and morphological differentiation in Streptomyces.In this study,we investigated the role of wblI(SCO5046),a member of this family,in the regulation of secondary metabolite production in Streptomyces lividans,a weak antibiotic producer.The over-expression of wblI was correlated with an enhanced biosynthesis of undecylprodigiosin and actinorhodin and with a reduction of the biosynthesis of y CPK and of the grey spore pigment encoded by the whi E locus.Five regulatory targets of Wbl I were identified using in vitro formaldehyde crosslinking and confirmed by EMSA and q RT-PCR.These included the promoter regions of wblI itself,two genes of the ACT cluster(act VA3 and the intergenic region between the divergently orientated genes act II-1 and act II-2)and that of wbl A,another member of the Wbl family.Quantitative RTPCR analysis indicated that the expression of act VA3 encoding a protein of unknown function as well as that of act II-1,a Tet R regulator repressing the expression of act II-2,encoding the ACT transporter,were down regulated in the Wbl I over-expressing strain.Consistently the expression of the transporter act II-2 was up-regulated.The expression of Wbl A,which is known to have a negative impact on ACT biosynthesis,was strongly down regulated in the Wbl I over-expressing strain.These data are consistent with the positive impact that Wbl I over-expression has on ACT biosynthesis.The latter might result from direct activation of ACT biosynthesis and export and from repression of the expression of Wbl A,a likely indirect,repressor of ACT biosynthesis.This study provided a better understanding to the specific role of Wbl I in the complex regulation of secondary metabolisms in the model Streptomyces strain,and more importantly,the reasons leading to the weak capabilities of Streptomyces lividans to produce antibiotic were addressed.This understanding should open the possibility,in the future,to transform each Streptomyces strain to over-producing strain by appropriate genetic engineering strategies and thus facilitate the discovery of most needed novel antibiotics.