SAV742, a Novel AraC-Family Regulator from Streptomyces avermitilis, Controls Avermectin Biosynthesis, Cell Growth and Development

Abstract

Avermectins are useful anthelmintic antibiotics produced by Streptomyces avermitilis. We demonstrated that a novel AraC-family transcriptional regulator in this species, SAV742, is a global regulator that negatively controls avermectin biosynthesis and cell growth, but positively controls morphological differentiation. Deletion of its gene, sav_742, increased avermectin production and dry cell weight, but caused delayed formation of aerial hyphae and spores. SAV742 directly inhibited avermectin production by repressing transcription of ave structural genes, and also directly regulated its own gene (sav_742) and adjacent gene sig8 (sav_741). The precise SAV742-binding site on its own promoter region was determined by DNase I footprinting assay coupled with site-directed DNA mutagenesis, and 5-nt inverted repeats (GCCGA-n10/n12-TCGGC) were found to be essential for SAV742 binding. Similar 5-nt inverted repeats separated by 3, 10 or 15 nt were found in the promoter regions of target ave genes and sig8. The SAV742 regulon was predicted based on bioinformatic analysis. Twenty-six new SAV742 targets were identified and experimentally confirmed, including genes involved in primary metabolism, secondary metabolism and development. Our findings indicate that SAV742 plays crucial roles in not only avermectin biosynthesis but also coordination of complex physiological processes in S. avermitilis.

A Novel AdpA Homologue Negatively Regulates Morphological Differentiation in Streptomyces xiamenensis 318

“…To elucidate the negative effect of AdpA Sx on morphological differentiation in S. xiamenensis 318, a multiple sequence alignment of AdpA homologues was performed. The result revealed that the amino acid sequence of AdpA Sx was highly similar to that of the well-studied AdpA (approximately 73%) except SVA742 (16%), which regulates secondary metabolite biosynthesis and morphological differentiation in S. avermitilis (25). Two conserved domains were detected in the alignment, a type 1 glutamine amidotransferase (GATase1) domain in the N terminus and a helix-turn-helix (HTH) DNA-binding domain, of the AraC family regulators, in the C terminus ( Fig.…”

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.…”

BldD, a master developmental repressor, activates antibiotic production in two Streptomyces species

“…Therefore, spores and mycelia of S. roseosporus strains grown on DA1 plates for 2, 4, or 6 days were observed by SEM. Preparation and examination of samples were performed as described previously (Sun et al , ).…”