An intricate regulation of Wbl A controlling production of silent tylosin analogues and abolishment of expressible nikkomycin

Genome sequencing has revealed that actinomycetes possess the potential to produce many more secondary metabolites than previously thought.The existing challenge is to devise efficient methods to activate these silent biosynthetic gene clusters(BGCs).In Streptomyces ansochromogenes,disruption of wbl A,a pleiotropic regulatory gene,activated the expression of cryptic tylosin analogues and abolished nikkomycin production simultaneously.Overexpressing pathway-specific regulatory genes tylR1 and tylR2 can also trigger the biosynthesis of silent tylosin analogues,in which TylR1 exerted its function via enhancing tylR2 expression.Bacterial one-hybrid system experiments unveiled that Wbl A directly inhibits the transcription of tylR1 and tylR2 to result in the silence of tylosin analogues BGC.Furthermore,Wbl A can activate the nikkomycin production through up-regulating the transcription of pleiotropic regulatory gene adp A.More interestingly,Adp A can activate san G(an activator gene in nikkomycin BGC)but repress wbl A.Our studies provide a valuable insight into the complex functions of pleiotropic regulators.

Multi-omics Data Reveal the Effect of Sodium Butyrate on Gene Expression and Protein Modification in Streptomyces

Streptomycetes possess numerous gene clusters and the potential to produce a large amount of natural products.Histone deacetylase(HDAC)inhibitors play an important role in the regulation of histone modifications in fungi,but their roles in prokaryotes remain poorly understood.Here,we investigated the global effects of the HDAC inhibitor,sodium butyrate(SB),on marine-derived Streptomyces olivaceus FXJ 8.021,particularly focusing on the activation of secondary metabolite biosynthesis.The antiSMASH analysis revealed 33 secondary metabolite biosynthetic gene clusters(BGCs)in strain FXJ 8.021,among which the silent lobophorin BGC was activated by SB.Transcriptomic data showed that the expression of genes involved in lobophorin biosynthesis(ge00097–ge00139)and CoA-ester formation(e.g.,ge02824),as well as the glycolysis/gluconeogenesis pathway(e.g.,ge01661),was significantly up-regulated in the presence of SB.Intracellular CoA-ester analysis confirmed that SB triggered the biosynthesis of CoA-ester,thereby increasing the precursor supply for lobophorin biosynthesis.Further acetylomic analysis revealed that the acetylation levels on 218 sites of 190 proteins were up-regulated and those on 411 sites of 310 proteins were down-regulated.These acetylated proteins were particularly enriched in transcriptional and translational machinery components(e.g.,elongation factor GE04399),and their correlations with the proteins involved in lobophorin biosynthesis were established by protein–protein interaction network analysis,suggesting that SB might function via a complex hierarchical.

Quantitative characterization of filamentous fungal promoters on a single-cell resolution to discover cryptic natural products

Characterization of filamentous fungal regulatory elements remains challenging because of time-consuming transformation technologies and limited quantitative methods.Here we established a method for quantitative assessment of filamentous fungal promoters based on flow cytometry detection of the superfolder green fluorescent protein at single-cell resolution.Using this quantitative method,we acquired a library of 93 native promoter elements from Aspergillus nidulans in a high-throughput format.The strengths of identified promoters covered a 37-fold range by flow cytometry.P_(zipA) and P_(sltA)were identified as the strongest promoters,which were 2.9-and 1.5-fold higher than that of the commonly used constitutive promoter P_(gpdA).Thus,we applied P_(zipA)and P_(sltA)to activate the silent nonribosomal peptide synthetase gene Afpes1 from Aspergillus fumigatus in its native host and the heterologous host A.nidulans.The metabolic products of Afpes1 were identified as new cyclic tetrapeptide derivatives,namely,fumiganins A and B.Our method provides an innovative strategy for natural product discovery in fungi.

Genome mining combined metabolic shunting and OSMAC strategy of an endophytic fungus leads to the production of diverse natural products

Endophytic fungi are promising producers of bioactive small molecules.Bioinformatic analysis of the genome of an endophytic fungus Penicillium dangeardii revealed 43 biosynthetic gene clusters,exhibited its strong ability to produce numbers of secondary metabolites.However,this strain mainly produce rubratoxins alone with high yield in varied culture conditions,suggested most gene clusters are silent.Efforts for mining the cryptic gene clusters in P.dangeardii,including epigenetic regulation and one-strain-many-compounds(OSMAC)approach were failed probably due to the high yield of rubratoxins.A metabolic shunting strategy by deleting the key gene for rubratoxins biosynthesis combining with optimization of culture condition successfully activated multiple silent genes encoding for other polyketide synthases(PKSs),and led to the trace compounds detectable.As a result,a total of 23 new compounds including azaphilone monomers,dimers,turimers with unprecedented polycyclic bridged heterocycle and spiral structures,as well as siderophores were identified.Some compounds showed significant cytotoxicities,anti-inflammatory or antioxidant activities.The attractive dual PKS s gene clusters for azaphilones biosynthesis were mined by bioinformatic analysis and overexpression of a pathway specific transcription factor.Our work therefor provides an efficient approach to mine the chemical diversity of endophytic fungi.