AvaR2, a pseudo γ‐butyrolactone receptor homologue from Streptomyces avermitilis, is a pleiotropic repressor of avermectin and avenolide biosynthesis and cell growth

Abstract

Avermectins produced by Streptomyces avermitilis are effective anthelmintic agents. The autoregulatory signalling molecule that triggers avermectin biosynthesis is a novel butenolide-type molecule, avenolide, rather than common γ-butyrolactones (GBLs). We identified AvaR2, a pseudo GBL receptor homologue, as an important repressor of avermectin and avenolide biosynthesis and cell growth. AvaR2 directly repressed transcription of aveR (the ave cluster-situated activator gene), aco (a key gene for avenolide biosynthesis), its own gene (avaR2) and two other GBL receptor homologous genes (avaR1 and avaR3) by binding to their promoter regions. The aveR promoter had the highest affinity for AvaR2. A consensus 18 bp ARE (autoregulatory element)-like sequence was found in the AvaR2-binding regions of these five target genes. Eleven novel AvaR2 targets were identified, including genes involved in primary metabolism, ribosomal protein synthesis, and stress responses. AvaR2 bound and responded to endogenous avenolide and exogenous antibiotics jadomycin B (JadB) and aminoglycosides to modulate its DNA-binding activity. Our findings help to clarify the roles of pseudo GBL receptors as pleiotropic regulators and as receptors for new type autoregulator and exogenous antibiotic signal. A pseudo GBL receptor-mediated antibiotic signalling transduction system may be a common strategy that facilitates Streptomyces interspecies communication and survival in complex environments.

wblA , a pleiotropic regulatory gene modulating morphogenesis and daptomycin production in Streptomyces roseosporus

“…The cell pellet was washed with distilled water, collected by centrifugation and dried to constant weight (Zhu et al . ).…”

An Alternative σ Factor, σ8, Controls Avermectin Production and Multiple Stress Responses in Streptomyces avermitilis

“…The finding that σ 8 indirectly represses ave genes suggested that σ 8 initiates transcription of direct repressor(s) of aveR or aveA1 . We recently characterized PhoP (Yang et al, 2015) and AvaR2 (Zhu et al, 2016) as direct repressors of aveR . We also found that SAV742 directly represses transcription of several ave structural genes including aveA1 , but not aveR (Sun et al, 2016).…”

“…The observation that σ 8 has an indirect effect on aveR expression suggests that it regulates aveR through a “cascade” mechanism. However, our search for aveR upstream regulator(s) that mediate the repression of σ 8 on aveR showed that the two known aveR direct repressor genes, phoP (Yang et al, 2015) and avaR2 (Zhu et al, 2016), are not targets of σ 8 . Future studies will identify such direct regulator(s) of aveR and clarify the mechanisms underlying σ 8 function in avermectin production.…”

Sodium Lactate Negatively Regulates Shewanella putrefaciens CN32 Biofilm Formation via a Three-Component Regulatory System (LrbS-LrbA-LrbR)

“…Two single mutants of Sputcn32_0304 and Sputcn32_0305, Δ0304 and Δ0305, were constructed. The deletion mutant of Sputcn32_0304 was constructed according to previous studies (39)(40)(41), which can avoid the polar effect on expression of the downstream gene Sputcn32_0303 and facilitate the investigation on its own expression changes. The biofilm biomasses of both single mutants were significantly increased compared to that of the WT strain, and biofilms of both complementation strains C-0304 and C-0305 were restored to the WT level ( Fig.…”

“…All other deletion mutants were constructed according to previous studies (39)(40)(41). To construct the Δ0304 mutant, PCR was used to generate a 1,587-bp DNA fragment upstream (positions Ϫ1443 to 144 relative to the Sputcn32_0304 start codon) and a 1,529-bp DNA fragment downstream (positions 565 to 2094 relative to the Sputcn32_0304 start codon) of the Sputcn32_0304 gene (reserving 144 bp after the start codon for real-time RT-PCR analysis) using primers 0304-5F/0304-5R and 0304-3F/0304-3R, respectively.…”