title: Increasing Avermectin Production in Streptomyces avermitilis by Manipulating the Expression of a Novel TetR-Family Regulator and Its Target Gene Product.
abstract: Avermectins produced by Streptomyces avermitilis are commercially important anthelmintic agents. The detailed regulatory mechanisms of avermectin biosynthesis remain unclear. Here, we identified SAV3619, a TetR-family transcriptional regulator designated AveT, to be an activator for both avermectin production and morphological differentiation in S. avermitilis. AveT was shown to indirectly stimulate avermectin production by affecting transcription of the cluster-situated activator gene aveR. AveT directly repressed transcription of its own gene (aveT), adjacent gene pepD2 (sav_3620), sav_7490 (designated aveM), and sav_7491 by binding to an 18-bp perfect palindromic sequence (CGAAACGKTKYCGTTTCG, where K is T or G and Y is T or C and where the underlining indicates inverted repeats) within their promoter regions. aveM (which encodes a putative transmembrane efflux protein belonging to the major facilitator superfamily [MFS]), the important target gene of AveT, had a striking negative effect on avermectin production and morphological differentiation. Overexpression of aveT and deletion of aveM in wild-type and industrial strains of S. avermitilis led to clear increases in the levels of avermectin production. In vitro gel-shift assays suggested that C-5-O-B1, the late pathway precursor of avermectin B1, acts as an AveT ligand. Taken together, our findings indicate positive-feedback regulation of aveT expression and avermectin production by a late pathway intermediate and provide the basis for an efficient strategy to increase avermectin production in S. avermitilis by manipulation of AveT and its target gene product, AveM.
authors.affiliation: State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Wenshuai
authors.initials: W
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Qinling
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Jilun
authors.initials: J
authors.lastname: Li
authors.affiliation: State Key Laboratory of Agro-Biotechnology and MOA Key Laboratory of Soil Microbiology, College of Biological Sciences, China Agricultural University, Beijing, China wen@cau.edu.cn.
authors.forename: Ying
authors.initials: Y
authors.lastname: Wen
mesh_terms: D000871:Anthelmintics / Q000378:metabolism*; D004269:DNA, Bacterial / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D002141:Encephalitis Virus, California; D017353:Gene Deletion; D015870:Gene Expression; D015964:Gene Expression Regulation, Bacterial; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000378:metabolism; D060847:Metabolic Engineering; D011485:Protein Binding; D013302:Streptomyces / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D000871:Anthelmintics; D004269:DNA, Bacterial; D014157:Transcription Factors; D007559:Ivermectin; C019264:avermectin