Transcription Factor Engineering in Leads to the Discovery of an Orsellinaldehyde Derivative Produced via an Unlinked Polyketide Synthase Gene.

Secondary metabolites are generally produced by enzymes encoded by genes within a biosynthetic gene cluster. Transcription factor genes are frequently located within these gene clusters. These transcription factors often drive expression of the other genes of the biosynthetic gene cluster, and overexpression of the transcription factor provides a facile approach to express all genes within a gene cluster, resulting in production of downstream metabolite(s).

A heterologous expression platform in for the elucidation of cryptic secondary metabolism biosynthetic gene clusters: discovery of the sartorypyrone biosynthetic pathway.

is a serious human pathogen causing life-threatening Aspergillosis in immunocompromised patients. Secondary metabolites (SMs) play an important role in pathogenesis, but the products of many SM biosynthetic gene clusters (BGCs) remain unknown. In this study, we have developed a heterologous expression platform in , using a newly created genetic dereplication strain, to express a previously unknown BGC from and determine its products.

Polystyrene Upcycling into Fungal Natural Products and a Biocontrol Agent.

Polystyrene (PS) is one of the most used yet infrequently recycled plastics. Although manufactured on the scale of 300 million tons per year globally, current approaches toward PS degradation are energy- and carbon-inefficient, slow, and/or limited in the value that they reclaim. We recently reported a scalable process to degrade post-consumer polyethylene-containing waste streams into carboxylic diacids.

Conversion of Polyethylenes into Fungal Secondary Metabolites.

Waste plastics represent major environmental and economic burdens due to their ubiquity, slow breakdown rates, and inadequacy of current recycling routes. Polyethylenes are particularly problematic, because they lack robust recycling approaches despite being the most abundant plastics in use today. We report a novel chemical and biological approach for the rapid conversion of polyethylenes into structurally complex and pharmacologically active compounds.

Total Heterologous Biosynthesis of Fungal Natural Products in .

Fungal natural products comprise a wide range of bioactive compounds including important drugs and agrochemicals. Intriguingly, bioinformatic analyses of fungal genomes have revealed that fungi have the potential to produce significantly more natural products than what have been discovered so far. It has thus become widely accepted that most biosynthesis pathways of fungal natural products are silent or expressed at very low levels under laboratory cultivation conditions.

Characterization of a silent azaphilone biosynthesis gene cluster in Aspergillus terreus NIH 2624.

Filamentous fungal secondary metabolites are an important source of bioactive components. Genome sequencing ofAspergillus terreusrevealed many silent secondary metabolite biosynthetic gene clusters presumed to be involved in producing secondary metabolites. Activation of silent gene clusters through overexpressing a pathway-specific regulator is an effective avenue for discovering novel fungal secondary metabolites.

The sexual spore pigment asperthecin is required for normal ascospore production and protection from UV light in Aspergillus nidulans.

Many fungi develop both asexual and sexual spores that serve as propagules for dissemination and/or recombination of genetic traits. Asexual spores are often heavily pigmented and this pigmentation provides protection from UV light. However, little is known about any purpose pigmentation that may serve for sexual spores.

Identification of the pigment and its role in UV resistance in Paecilomyces variotii, a Chernobyl isolate, using genetic manipulation strategies.

Fungi produce secondary metabolites that are not directly involved in their growth, but often contribute to their adaptation to extreme environmental stimuli and enable their survival. Conidial pigment or melanin is one of the secondary metabolites produced naturally by a polyketide synthesis (PKS) gene cluster in several filamentous fungi and is known to protect these fungi from extreme radiation conditions. Several pigmented or melanized fungi have been shown to grow under extreme radiation conditions at the Chernobyl nuclear accident site.

An Platform for the Complete Cluster Refactoring and Total Biosynthesis of Fungal Natural Products.

Fungal natural products (NPs) comprise a vast number of bioactive molecules with diverse activities, and among them are many important drugs. However, the yields of fungal NPs from native producers are usually low, and total synthesis of structurally complex NPs is challenging. As such, downstream derivatization and optimization of lead fungal NPs can be impeded by the high cost of obtaining sufficient starting material.

Metabolomic Analysis of Isolated From the International Space Station Reveals Enhanced Production Levels of the Antioxidant Pyranonigrin A.

Secondary metabolite (SM) production in JSC-093350089, isolated from the International Space Station (ISS), is reported, along with a comparison to the experimentally established strain ATCC 1015. The analysis revealed enhanced production levels of naphtho-γ-pyrones and therapeutically relevant SMs, including bicoumanigrin A, aurasperones A and B, and the antioxidant pyranonigrin A. Genetic variants that may be responsible for increased SM production levels in JSC-093350089 were identified.

International Space Station conditions alter genomics, proteomics, and metabolomics in Aspergillus nidulans.

The first global genomic, proteomic, and secondary metabolomic characterization of the filamentous fungus Aspergillus nidulans following growth onboard the International Space Station (ISS) is reported. The investigation included the A. nidulans wild-type and three mutant strains, two of which were genetically engineered to enhance secondary metabolite production.

Hybrid Transcription Factor Engineering Activates the Silent Secondary Metabolite Gene Cluster for (+)-Asperlin in Aspergillus nidulans.

Fungi are a major source of valuable bioactive secondary metabolites (SMs). These compounds are synthesized by enzymes encoded by genes that are clustered in the genome. The vast majority of SM biosynthetic gene clusters are not expressed under normal growth conditions, and their products are unknown.

Discovery and Elucidation of the Biosynthesis of Aspernidgulenes: Novel Polyenes from Aspergillus Nidulans by Using Serial Promoter Replacement.

Through serial promoter exchanges, we isolated several novel polyenes, the aspernidgulenes, from Aspergillus nidulans and uncovered their succinct biosynthetic pathway involving only four enzymes. An enoyl reductase (ER)-less highly reducing polyketide synthase (HR-PKS) putatively produces a 5,6-dihydro-α-pyrone polyene, which undergoes bisepoxidation, epoxide ring opening, cyclization, and hydrolytic cleavage by three tailoring enzymes to generate aspernidgulene A1 and A2. Our findings demonstrate the prowess of fungal-tailoring enzymes to transform a polyketide scaffold concisely and efficiently into complex structures.

Baicalein Targets GTPase-Mediated Autophagy to Eliminate Liver Tumor-Initiating Stem Cell-Like Cells Resistant to mTORC1 Inhibition.

Drug resistance is a major problem in the treatment of liver cancer. Mammalian Target of Rapamycin 1 (mTORC1) inhibitors have been tested for the treatment of liver cancer based on hyperactive mTOR in this malignancy. However, their clinical trials showed poor outcome, most likely due to their ability to upregulate CD133 and promote chemoresistance.

Butyrate influences intracellular levels of adenine and adenine derivatives in the fungus Penicillium restrictum.

Butyrate, a small fatty acid, has an important role in the colon of ruminants and mammalians including the inhibition of inflammation and the regulation of cell proliferation. There is also growing evidence that butyrate is influencing the histone structure in mammalian cells by inhibition of histone deacetylation. Butyrate shows furthermore an antimicrobial activity against fungi, yeast and bacteria, which is linked to its toxicity at a high concentration.

Overexpression of a three-gene conidial pigment biosynthetic pathway in Aspergillus nidulans reveals the first NRPS known to acetylate tryptophan.

Fungal nonribosomal peptide synthetases (NRPSs) are megasynthetases that produce cyclic and acyclic peptides. In Aspergillus nidulans, the NRPS ivoA (AN10576) has been associated with the biosynthesis of grey-brown conidiophore pigments. Another gene, ivoB (AN0231), has been demonstrated to be an N-acetyl-6-hydroxytryptophan oxidase that putatively acts downstream of IvoA.

Discovery of McrA, a master regulator of Aspergillus secondary metabolism.

Fungal secondary metabolites (SMs) are extremely important in medicine and agriculture, but regulation of their biosynthesis is incompletely understood. We have developed a genetic screen in Aspergillus nidulans for negative regulators of fungal SM gene clusters and we have used this screen to isolate mutations that upregulate transcription of the non-ribosomal peptide synthetase gene required for nidulanin A biosynthesis. Several of these mutations are allelic and we have identified the mutant gene by genome sequencing.

Resistance Gene-Guided Genome Mining: Serial Promoter Exchanges in Aspergillus nidulans Reveal the Biosynthetic Pathway for Fellutamide B, a Proteasome Inhibitor.

Fungal genome projects are revealing thousands of cryptic secondary metabolism (SM) biosynthetic gene clusters that encode pathways that potentially produce valuable compounds. Heterologous expression systems should allow these clusters to be expressed and their products obtained, but approaches are needed to identify the most valuable target clusters. The inp cluster of Aspergillus nidulans contains a gene, inpE, that encodes a proteasome subunit, leading us to hypothesize that the inp cluster produces a proteasome inhibitor and inpE confers resistance to this compound.

Biosynthetic Pathway of the Reduced Polyketide Product Citreoviridin in Aspergillus terreus var. aureus Revealed by Heterologous Expression in Aspergillus nidulans.

Citreoviridin (1) belongs to a class of F1-ATPase β-subunit inhibitors that are synthesized by highly reducing polyketide synthases. These potent mycotoxins share an α-pyrone polyene structure, and they include aurovertin, verrucosidin, and asteltoxin. The identification of the citreoviridin biosynthetic gene cluster in Aspergillus terreus var.

Correction: Genome mining and molecular characterization of the biosynthetic gene cluster of a diterpenic meroterpenoid, 15-deoxyoxalicine B, in .

[This corrects the article DOI: 10.1039/C5SC01965F.].

Development of Genetic Dereplication Strains in Aspergillus nidulans Results in the Discovery of Aspercryptin.

To reduce the secondary metabolite background in Aspergillus nidulans and minimize the rediscovery of compounds and pathway intermediates, we created a "genetic dereplication" strain in which we deleted eight of the most highly expressed secondary metabolite gene clusters (more than 244,000 base pairs deleted in total). This strain allowed us to discover a novel compound that we designate aspercryptin and to propose a biosynthetic pathway for the compound. Interestingly, aspercryptin is formed from compounds produced by two separate gene clusters, one of which makes the well-known product cichorine.

Rational domain swaps reveal insights about chain length control by ketosynthase domains in fungal nonreducing polyketide synthases.

A facile genetic methodology in the filamentous fungus Aspergillus nidulans allowed exchange of the starter unit ACP transacylase (SAT) domain in the nonreduced polyketide synthase (NR-PKS) AfoE of the asperfuranone pathway with the SAT domains from 10 other NR-PKSs. The newly created hybrid with the NR-PKS AN3386 is able to accept a longer starter unit in place of the native substrate to create a novel aromatic polyketide in vivo.

Inhibition of Tau aggregation by three Aspergillus nidulans secondary metabolites: 2,ω-dihydroxyemodin, asperthecin, and asperbenzaldehyde.

The aggregation of the microtubule-associated protein tau is a significant event in many neurodegenerative diseases including Alzheimer's disease. The inhibition or reversal of tau aggregation is therefore a potential therapeutic strategy for these diseases. Fungal natural products have proven to be a rich source of useful compounds having wide varieties of biological activity.