Streptomyces can produce numerous antibiotics and many other bioactive compounds.Recently,the molecular mechanisms of transcriptional regulators in control of antibiotic production by influencing the expression of bio...Streptomyces can produce numerous antibiotics and many other bioactive compounds.Recently,the molecular mechanisms of transcriptional regulators in control of antibiotic production by influencing the expression of biosynthetic gene clusters(BGCs)have been extensively studied.However,for regulators that affect both antibiotic production and cell growth,the way to influence antibiotic production may be diverse,but related studies are limited.Here,based on time-course transcriptome analysis,a four-component system,SbrH1-R,consisting of the two-component system SbrKR(SBI_03479/3478)and two hypothetical proteins SbrH1(SBI_03481)and SbrH2(SBI_03480)potentially related with the biosynthesis of milbemycins was identified in Streptomyces bingchenggensis BC-101-4.Deletion of sbrH1-R resulted in weakened cell growth but a 110%increase of milbemycin production compared with that in BC-101-4.Comparative transcriptome analyses of the sbrH1-R mutant and BC-101-4 revealed that SbrH1-R not only indirectly represses milbemycin BGC expression,but also inhibits milbemycin production by modulating expression levels of genes related to precursor supply and antibiotic efflux.Further genetic experiments identified several new targets,including five precursor supply-associated reactions/pathways(e.g.,the reaction from pyruvate to acetyl-CoA,the reaction from acetyl-CoA to citrate,the fatty acidβ-oxidation process,and the branched chain amino acid and phenylalanine acid degradation pathways)and a milbemycin exporter system(MilEX2)that can be engineered for milbemycin overproduction.These results shed new light on the understanding of regulation of milbemycin biosynthesis and provide useful targets for future metabolic engineering of the native host to improve milbemycin production.展开更多
The TetR family of regulators are an important group of transcription regulators that regulate diverse cellular processes in prokaryotes.In this study,we found that XNR_0706,a TetR family regulator,controlled the expr...The TetR family of regulators are an important group of transcription regulators that regulate diverse cellular processes in prokaryotes.In this study,we found that XNR_0706,a TetR family regulator,controlled the expression of XNR_0345,XNR_0454,XNR_0513 and XNR_1438 putatively involved in fatty acidβ-oxidation by interacting with the promoter regions in Streptomyces albus B4.The transcription level of these four genes was downregulated in XNR_0706 deletion strain(ΔXNR_0706)and restored by XNR_0706 complementation inΔ0706/pIB-0706,demonstrating that XNR_0706 was a positive transcriptional regulator of the genes.With toxic long-chain fatty acids addition in TSB media,deletion of XNR_0706 caused significantly poor growth,whereas XNR_0706 complementation increased the utilization of additional fatty acids,resulting in restored growth.Fatty acidβ-oxidation is one source of acetyl-and malonyl-CoA precursors for polyketides biosynthesis in actino-bacteria.Overexpression of XNR_0706 in B4/spnNEW,a spinosad heterologous expression strain derived from S.albus B4,increased spinosad yield by 20.6%.Additionally,supplement of 0.3 g/L fatty acids resulted in a further 42.4%increase in spinosad yield.Our study reveals a regulatory mechanism in long-chain fatty acids metabolism in S.albus and these insights into the molecular regulation ofβ-oxidation by XNR_0706 are instrumental for increasing secondary metabolites in actinobacteria.展开更多
基金This work was financially supported by National Natural Science Foundation of China(31872936,31972291,and 31972348).
文摘Streptomyces can produce numerous antibiotics and many other bioactive compounds.Recently,the molecular mechanisms of transcriptional regulators in control of antibiotic production by influencing the expression of biosynthetic gene clusters(BGCs)have been extensively studied.However,for regulators that affect both antibiotic production and cell growth,the way to influence antibiotic production may be diverse,but related studies are limited.Here,based on time-course transcriptome analysis,a four-component system,SbrH1-R,consisting of the two-component system SbrKR(SBI_03479/3478)and two hypothetical proteins SbrH1(SBI_03481)and SbrH2(SBI_03480)potentially related with the biosynthesis of milbemycins was identified in Streptomyces bingchenggensis BC-101-4.Deletion of sbrH1-R resulted in weakened cell growth but a 110%increase of milbemycin production compared with that in BC-101-4.Comparative transcriptome analyses of the sbrH1-R mutant and BC-101-4 revealed that SbrH1-R not only indirectly represses milbemycin BGC expression,but also inhibits milbemycin production by modulating expression levels of genes related to precursor supply and antibiotic efflux.Further genetic experiments identified several new targets,including five precursor supply-associated reactions/pathways(e.g.,the reaction from pyruvate to acetyl-CoA,the reaction from acetyl-CoA to citrate,the fatty acidβ-oxidation process,and the branched chain amino acid and phenylalanine acid degradation pathways)and a milbemycin exporter system(MilEX2)that can be engineered for milbemycin overproduction.These results shed new light on the understanding of regulation of milbemycin biosynthesis and provide useful targets for future metabolic engineering of the native host to improve milbemycin production.
基金support from the National Key Research and Development Program of China(No.2018YFA0900404).
文摘The TetR family of regulators are an important group of transcription regulators that regulate diverse cellular processes in prokaryotes.In this study,we found that XNR_0706,a TetR family regulator,controlled the expression of XNR_0345,XNR_0454,XNR_0513 and XNR_1438 putatively involved in fatty acidβ-oxidation by interacting with the promoter regions in Streptomyces albus B4.The transcription level of these four genes was downregulated in XNR_0706 deletion strain(ΔXNR_0706)and restored by XNR_0706 complementation inΔ0706/pIB-0706,demonstrating that XNR_0706 was a positive transcriptional regulator of the genes.With toxic long-chain fatty acids addition in TSB media,deletion of XNR_0706 caused significantly poor growth,whereas XNR_0706 complementation increased the utilization of additional fatty acids,resulting in restored growth.Fatty acidβ-oxidation is one source of acetyl-and malonyl-CoA precursors for polyketides biosynthesis in actino-bacteria.Overexpression of XNR_0706 in B4/spnNEW,a spinosad heterologous expression strain derived from S.albus B4,increased spinosad yield by 20.6%.Additionally,supplement of 0.3 g/L fatty acids resulted in a further 42.4%increase in spinosad yield.Our study reveals a regulatory mechanism in long-chain fatty acids metabolism in S.albus and these insights into the molecular regulation ofβ-oxidation by XNR_0706 are instrumental for increasing secondary metabolites in actinobacteria.
