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Microbial communication has attracted notable attention as an indicator of microbial interactions that lead to marked alterations of secondary metabolites (SMs) in varied environments. However, the mechanisms responsible for SM regulation are not fully understood, especially in fungal-fungal interactions. Here, cocultivation of an endophytic fungus Epicoccum dendrobii with the model fungus Aspergillus nidulans and several other filamentous fungi triggered widespread alteration of SMs. Multiple silent biosynthetic gene clusters in A. nidulans were activated by transcriptome and metabolome analysis. Unprecedentedly, gene deletion and replacement proved that a partial loss-of-function VeA1 protein, but not VeA, was associated with the widespread SM changes in both A. nidulans and A. fumigatus during cocultivation. VeA1 regulation required the transcription factor SclB and the velvet complex members LaeA and VelB for producing aspernidines as representative formation of SMs in A. nidulans . This study provides new insights into the mechanism that trigger metabolic changes during fungal-fungal interactions.

The strategies of genetic dereplication and manipulation of epigenetic regulators to activate the cryptic gene clusters are effective to discover natural products with novel structure in filamentous fungi. In this study, a combination of genetic dereplication (deletion of pesthetic acid biosynthetic gene, PfptaA) and manipulation of epigenetic regulators (deletion of histone methyltransferase gene PfcclA and histone deacetylase gene PfhdaA) was developed in plant endophytic fungus Pestalotiopsis fici. The deletion of PfptaA with PfcclA and/or PfhdaA led to isolation of 1 novel compound, pestaloficiol X (1), as well as another 11 known compounds with obvious yield changes. The proposed biosynthesis pathway of pestaloficiol X was speculated using comparative analysis of homologous biosynthetic gene clusters. Moreover, phenotypic effects on the conidial development and response to oxidative stressors in the mutants were explored. Our results revealed that the new strain with deletion of PfcclA or PfhdaA in ΔPfptaA background host can neutralise the hyperformation of conidia in the PfptaA mutant, and that the ΔPfptaA ΔPfhdaA mutant was generally not sensitive to oxidative stressors as much as the ΔPfptaA ΔcclA mutant in comparison with the single mutant ΔPfptaA or the parental strains. This combinatorial approach can be applied to discover new natural products in filamentous fungi.

The attachment of a dimethylallyl moiety to C4 of 1,3-dihydroxynaphthalene led to spontaneous oxidative cyclisations, resulting in the formation of two tetrahydrobenzofuran and one bicyclo[3.3.1]nonane derivatives. Incubation under an 18O-rich atmosphere proved that both the incorporated oxygen atoms originated from O2. A radical-involved mechanism is proposed for these cyclisations.

The biosynthetic pathway of the prenylated salicylaldehyde flavoglaucin and congeners in Aspergillus ruber was elucidated by genome mining, heterologous expression, precursor feeding, and biochemical characterization. The polyketide skeleton was released as alkylated salicyl alcohols, which is a prerequisite for consecutive hydroxylation and prenylation, before reoxidation to the final aldehyde products. Our results provide an excellent example for a highly programmed machinery in natural product biosynthesis.

Prenylation of cyclodipeptides contributes largely to the structure diversification and biological activity. The prenylated products can be further metabolized by modifications like hydroxylation with cytochrome P450 enzymes or nonheme FeII/2-oxoglutarate-dependent oxygenases. Herein, we cloned and overexpressed NFIA_045530 from Neosartorya fischeri, which shares high sequence similarity with the nonheme FeII/2-oxoglutarate-dependent oxygenase FtmOx1Af from Aspergillus fumigatus on the amino acid level. FtmOx1Af is a member of the biosynthetic enzymes for fumitremorgin-type mycotoxins and catalyzes the conversion of fumitremorgin B to verruculogen by insertion of an oxygen molecule into the two prenyl moieties. The recombinant protein EAW25734 encoded by NFIA_045530 was purified to apparent homogeneity and then was used for incubation with intermediates of the fumitremorgin biosynthetic pathway. LC-MS analysis revealed no consumption of fumitremorgin B but good conversion with its biosynthetic precursor t...

Prenylation of cyclodipeptides contributes largely to the structure diversification and biological activity. The prenylated products can be further metabolized by modifications like hydroxylation with cytochrome P450 enzymes or nonheme Fe

A phylogeny-guided approach was applied to screen endophytic fungi containing type I polyketide synthase (PKS I) biosynthetic gene sequences and aimed to correlate genotype to chemotype for the discovery of novel bioactive polyketides. Salicorn 58, which was identified as Talaromyces funiculosus based on its internal transcribed spacer (ITS) and ribosomal large-subunit (LSU) DNA sequences, showed significant target bands. A chemical investigation of the culture of Salicorn 58 was allowed for the isolation of a new polyketide, Talafun (1), and a new natural product, N-(2'-hydroxy-3'-octadecenoyl)-9-methyl-4,8-sphingadienin (2), together with six known compounds, including chrodrimanin A (3), chrodrimanin B (4), N-(4-hydroxy-2-methoxyphenyl) acetamide (5), butyl β-glucose (6), 3β,15β-dihydroxyl-(22E, 24R)-ergosta-5,8(14),22-trien-7-dione (7), and (3β,5a,8a,22E)-5,8-epidioxyergosta-6,22-dien-3-ol (8). Their chemical structures were elucidated by extensive spectroscopic analysis and electro circular dichroism (ECD) spectrum calculations. Antioxidant experiments revealed that compound 5 showed strong ABTS(+) radical scavenging activity with an IC50 value of 11.43 ± 1.61 μM and potent ferric reducing activity (FRAP assay) with FRAP value of 187.52 ± 2.97. Antimicrobial assays revealed that compounds 1 and 4 showed high levels of selectivity toward Escherichia coli with MIC values of 18 ± 0.40 and 43 ± 0.52 μM, respectively. Compounds 2 and 3 exhibited broad-spectrum antimicrobial activity against Staphylococcus aureus, Mycobacterium smegmatis, Micrococcus tetragenus, Mycobacterium phlei, and E. coli, respectively. The results from the current research highlight the advantage of phylogeny-guided pipeline for the screening of new polyketides from endophytic fungi containing PKS I genes.