Identification by gene deletion analysis of barB as a negative regulator controlling an early process of virginiamycin biosynthesis in Streptomyces virginiae

Abstract

The Streptomyces virginiae gamma-butyrolactone autoregulator virginiae butanolide is a low-molecular-weight Streptomyces hormone eliciting virginiamycin biosynthesis through its binding to the specific receptor protein, BarA. Immediately downstream of barA lies barB, the transcription of which is tightly repressed by BarA in the absence of virginiae butanolide and derepressed in its presence. Thus, BarB is next to BarA on the virginiae butanolide-BarA signaling cascade. An in-frame 279-bp deletion was introduced into the barB allele, which rendered it inactive by eliminating the majority of the coding region, including the helix-turn-helix DNA-binding motif. No significant change was observed with the Delta barB mutant with respect to the timing or amount of virginiae butanolide production, or the morphological differentiation on solid media, indicating that barB neither participates in virginiae butanolide biosynthesis nor in cytodifferentiation. In contrast, analysis of virginiamycin production in the Delta barB mutant revealed that production of both virginiamycin M(1) and virginiamycin S occurred immediately after virginiae butanolide production, 2-3 h earlier than in the wild-type strain, indicating that BarB participates in the temporal retardation of virginiamycin production after virginiae butanolide inactivates the repressor function of BarA. RT-PCR analysis of the transcription of several genes surrounding barA-barB by the Delta barB mutant indicated that BarB plays a negative regulatory role, directly or indirectly, in the transcription of barZ, vmsR, and orf5 located upstream of barB.

The role of the TetR-family transcriptional regulator Aur1R in negative regulation of the auricin gene cluster in Streptomyces aureofaciens CCM 3239

“…The highest similarity of the Aur1R DNA-binding domain was to members of the subfamily of c-butyrolactone autoregulator pseudo-receptors, e.g. JadR2 (Yang et al, 1995), TylQ , BarB (Matsuno et al, 2004) and AlpW (Bunet et al, 2008), which all constitute an independent branch in the phylogenetic tree of c-butyrolactone autoregulator receptors and likely do not bind c-butyrolactone autoregulators (Nishida et al, 2007). Like Aur1R, almost all the pseudoreceptors act as negative regulators of antibiotic production and play a role in the specific repression of pathwayspecific transcription activator genes of the particular secondary metabolite gene cluster.…”

“…c-butyrolactone autoregulator receptors (Matsuno et al, 2004;. Therefore, it seems likely that pseudo-receptor genes play a common role in the negative regulation of secondary metabolite biosynthesis as target genes of autoregulator receptors in the autoregulator signalling cascade.…”

γ-Butyrolactone autoregulator-receptor system involved in lankacidin and lankamycin production and morphological differentiation in Streptomyces rochei

“…SrrB is similar to TylQ (49 % identity) involved in tylosin production in Streptomyces fradiae and BarB (42 %) involved in virginiamycin synthesis in S. virginiae (Matsuno et al, 2004) (Fig. 3b).…”

Involvement of AlpV, a New Member of the Streptomyces Antibiotic Regulatory Protein Family, in Regulation of the Duplicated Type II Polyketide Synthase alp Gene Cluster in Streptomyces ambofaciens

“…In most cases, the pathway-specific regulators play a positive role in the transcription of the biosynthetic genes, although some act as transcriptional repressors (28,38,47).…”