Identification and Characterization of a δ-Cadinol Synthase Potentially Involved in the Formation of Boreovibrins in Boreostereum vibrans of Basidiomycota

Mutations in Aristolochene Synthase Promote Hydroxylation of Aristolochene in Aspergillus oryzae

A terpene synthase gene (mtas) from Menisporopsis theobromae BCC 4162 was heterologously expressed in Aspergillus oryzae NSAR1, resulting in the production of (+)-aristolochene. Mutations were introduced in MtAS at aromatic residues (Y83, F103, F169 and W323) surrounding the active site, which are critical for precursor cyclisation and intermediate stabilisation during aristolochene biosynthesis. Transformants harbouring mutated mtas, specifically F103W, F169A and F169W, produced (2R,4S,5R,7S)-2-hydroxyaristolochene as the major product, along with aristolochene and other tentative metabolites, including germacrene A and sesquiterpenoids. Feeding experiments with (+)-aristolochene in A. oryzae NSAR1 revealed that 2-hydroxyaristolochene was only detected in trace amounts. This suggests that the oxidation products observed in this study are predominantly catalysed or facilitated by the mutated MtAS, differing from in vitro studies of other mutated aristolochene synthases. These findings highlight the impact of enzyme mutations on sesquiterpene production and suggest potential strategies for enhancing the diversity of sesquiterpenoids.

Biosynthesis of fungal terpenoids

Covering: up to August 2023Terpenoids, which are widely distributed in animals, plants, and microorganisms, are a large group of natural products with diverse structures and various biological activities. They have made great contributions to human health as therapeutic agents, such as the anti-cancer drug paclitaxel and anti-malarial agent artemisinin. Accordingly, the biosynthesis of this important class of natural products has been extensively studied, which generally involves two major steps: hydrocarbon skeleton construction by terpenoid cyclases and skeleton modification by tailoring enzymes. Additionally, fungi (Ascomycota and Basidiomycota) serve as an important source for the discovery of terpenoids. With the rapid development of sequencing technology and bioinformatics approaches, genome mining has emerged as one of the most effective strategies to discover novel terpenoids from fungi. To date, numerous terpenoid cyclases, including typical class I and class II terpenoid cyclases as well as emerging UbiA-type terpenoid cyclases, have been identified, together with a variety of tailoring enzymes, including cytochrome P450 enzymes, flavin-dependent monooxygenases, and acyltransferases. In this review, our aim is to comprehensively present all fungal terpenoid cyclases identified up to August 2023, with a focus on newly discovered terpenoid cyclases, especially the emerging UbiA-type terpenoid cyclases, and their related tailoring enzymes from 2015 to August 2023.

Telomere-to-Telomere Genome Assembly of Tibetan Medicinal Mushroom Ganoderma leucocontextum and the First Copia Centromeric Retrotransposon in Macro-Fungi Genome

A complete telomere-to-telomere (T2T) genome has been a longstanding goal in the field of genomic research. By integrating high-coverage and precise long-read sequencing data using multiple assembly strategies, we present here the first T2T gap-free genome assembly of Ganoderma leucocontextum strain GL72, a Tibetan medicinal mushroom. The T2T genome, with a size of 46.69 Mb, consists 13 complete nuclear chromosomes and typical telomeric repeats (CCCTAA)n were detected at both ends of 13 chromosomes. The high mapping rate, uniform genome coverage, a complete BUSCOs of 99.7%, and base accuracy exceeding 99.999% indicate that this assembly represents the highest level of completeness and quality. Regions characterized by distinct structural attributes, including highest Hi-C interaction intensity, high repeat content, decreased gene density, low GC content, and minimal or no transcription levels across all chromosomes may represent potential centromeres. Sequence analysis revealed the first Copia centromeric retrotransposon in macro-fungi genome. Phylogenomic analysis identified that G. leucocontextum and G. tsugae diverged from the other Ganoderma species approximately 9.8-17.9 MYA. The prediction of secondary metabolic clusters confirmed the capability of this fungus to produce a substantial quantity of metabolites. This T2T gap-free genome will contribute to the genomic 'dark matter' elucidation and server as a great reference for genetics, genomics, and evolutionary studies of G. leucocontextum.

Molecular and Functional Analyses of Characterized Sesquiterpene Synthases in Mushroom-Forming Fungi

Sesquiterpenes are a type of abundant natural product with widespread applications in several industries. They are biosynthesized by sesquiterpene synthases (STSs). As valuable and abundant biological resources, mushroom-forming fungi are rich in new sesquiterpenes and STSs, which remain largely unexploited. In the present study, we collected information on 172 STSs from mushroom-forming fungi with experimentally characterized products from the literature and sorted them to develop a dataset. Furthermore, we analyzed and discussed the phylogenetic tree, catalytic products, and conserved motifs of STSs. Phylogenetic analysis revealed that the STSs were clustered into four clades. Furthermore, their cyclization reaction mechanism was divided into four corresponding categories. This database was used to predict 12 putative STS genes from the edible fungi Flammulina velutipes. Finally, three FvSTSs were selected to experimentally characterize their functions. FvSTS03 predominantly produced Δ-cadinol and FvSTS08 synthesized β-barbatene as the main product; these findings were consistent with those of the functional prediction analysis. A product titer of 78.8 mg/L β-barbatene was achieved in Saccharomyces cerevisiae via metabolic engineering. Our study findings will help screen or design STSs from fungi with specific product profiles as functional elements for applications in synthetic biology.

Phytotoxicity of Rich Oxygenated Terpenes Essential Oil of Prosopis farcta against the Weed Dactyloctenium aegyptium

Weeds are considered the main reason for crop yield loss in the world. Weed control and management include various treatments such as cultural, physical, chemical, and biological methods. Chemical control of weeds is the most common method; however, the application of commercial synthetic herbicides caused several dangerous hazards in the environment including the appearance of resistant weed biotypes. Prosopis farcta (Banks & Sol.) J.F.Macbr. (Family: Fabaceae), is a common weed plant in the Middle East, where it is hard to eliminate due to its deep and overlapped roots. On the other side, it has many traditional uses around the world. Herein, the essential oil (EO) of P. farcta above-ground parts was extracted via hydrodistillation techniques and then analyzed using gas chromatography-mass spectroscopy (GC-MS). From the GC-MS analysis, 47 compounds were identified with a relative concentration of 98.02%, including terpenes as the main components (95.08%). From overall identified compounds, cubenol (19.07%), trans-chrysanthenyl acetate (17.69%), torreyol (8.28%), davana ether (3.50%), camphor (3.35%), and farnesyl acetone (3.13%) represented the abundant constituents. Furthermore, the phytotoxic activity of the P. farcta EO was assessed against the weed Dactyloctenium aegyptium (L.) Willd. The EO of P. farcta, at a concentration of 100 µL L−1, significantly inhibited the germination, seedling shoot growth, and seedling root growth by 64.1, 64.0, and 73.4%, respectively. The results exhibited that the seedling root growth is the most affected followed by the seed germination and seedling shoot growth with respective IC50 at 64.5, 80.5, and 92.9 µL L−1. It can be concluded that weeds are not absolutely harmful, but they may have beneficial uses, such as, for example as a source of phytochemicals with application in weed control practices (bioherbicides). It is advised to conduct additional research to characterize the allelopathic action of the major chemicals in their pure form, either alone or in combination, against a variety of weeds.

Biosynthesis of Sesquiterpenes in Basidiomycetes: A Review

Sesquiterpenes are common small-molecule natural products with a wide range of promising applications and are biosynthesized by sesquiterpene synthase (STS). Basidiomycetes are valuable and important biological resources. To date, hundreds of related sesquiterpenoids have been discovered in basidiomycetes, and the biosynthetic pathways of some of these compounds have been elucidated. This review summarizes 122 STSs and 2 fusion enzymes STSs identified from 26 species of basidiomycetes over the past 20 years. The biological functions of enzymes and compound structures are described, and related research is discussed.

Biotechnological potential and initial characterization of two novel sesquiterpene synthases from Basidiomycota Coniophora puteana for heterologous production of δ-cadinol

Background

Terpene synthases are versatile catalysts in all domains of life, catalyzing the formation of an enormous variety of different terpenoid secondary metabolites. Due to their diverse bioactive properties, terpenoids are of great interest as innovative ingredients in pharmaceutical and cosmetic applications. Recent advances in genome sequencing have led to the discovery of numerous terpene synthases, in particular in Basidiomycota like the wood rotting fungus Coniophora puteana, which further enhances the scope for the manufacture of terpenes for industrial purposes.

Results

In this study we describe the identification of two novel (+)-δ-cadinol synthases from C. puteana, Copu5 and Copu9. The sesquiterpene (+)-δ-cadinol was previously shown to exhibit cytotoxic activity therefore having an application as possible, new, and sustainably sourced anti-tumor agent. In an Escherichia coli strain, optimized for sesquiterpene production, titers of 225 mg l⁻¹ and 395 mg l⁻¹, respectively, could be achieved. Remarkably, both enzymes share the same product profile thereby representing the first two terpene synthases from Basidiomycota with identical product profiles. We solved the crystal structure of Copu9 in its closed conformation, for the first time providing molecular details of sesquiterpene synthase from Basidiomycota. Based on the Copu9 structure, we conducted structure-based mutagenesis of amino acid residues lining the active site, thereby altering the product profile. Interestingly, the mutagenesis study also revealed that despite the conserved product profiles of Copu5 and Copu9 different conformational changes may accompany the catalytic cycle of the two enzymes. This observation suggests that the involvement of tertiary structure elements in the reaction mechanism(s) employed by terpene synthases may be more complex than commonly expected.

Conclusion

The presented product selectivity and titers of Copu5 and Copu9 may pave the way towards a sustainable, biotechnological production of the potentially new bioactive (+)-δ-cadinol. Furthermore, Copu5 and Copu9 may serve as model systems for further mechanistic studies of terpenoid catalysis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12934-022-01791-8.

Sesquiterpene Cyclases from the Basidiomycete Cerrena unicolor

Hundreds of terpenoids have been isolated from Basidiomycota, among them are volatile mono- and sesquiterpenes with amazing sensory qualities, representing a promising alternative to essential oils from endangered plant species. Sesquiterpene synthases (STS) appear to be an abundant class of enzymes in these fungi. The basidiomycete Cerrena unicolor, a known sesquiterpene producer, was in silico screened for sesquiterpene cyclases via homology Basic Local Alignment Search Tool searches. Cyclase genes identified were cloned and heterologously expressed in Escherichia coli Bl21 using pCOLD I as the expression vector. Ten cyclases were successfully produced and purified, and their identity was confirmed using amino acid sequencing of tryptic peptides by nano-liquid chromatography-high resolution-electrospray ionization-tandem mass spectrometry. Gas chromatography/mass spectrometry analysis was applied to characterize these cyclases according to the formation of sesquiterpene hydrocarbons and oxidized terpenoids. Bioinformatic characterization and phylogenetic determination allowed for the classification of these diverse fungal enzymes. A representative single and a multi-product STS, respectively, were further analyzed for their dependency from divalent metal cations as a cofactor for the catalytic activity.

Mind the mushroom: natural product biosynthetic genes and enzymes of Basidiomycota

Covering: up to September 2020 Mushroom-forming fungi of the division Basidiomycota have traditionally been recognised as prolific producers of structurally diverse and often bioactive secondary metabolites, using the methods of chemistry for research. Over the past decade, -omics technologies were applied on these fungi, and sophisticated heterologous gene expression platforms emerged, which have boosted research into the genetic and biochemical basis of the biosyntheses. This review provides an overview on experimentally confirmed natural product biosyntheses of basidiomycete polyketides, amino acid-derived products, terpenoids, and volatiles. We also present challenges and solutions particular to natural product research with these fungi. 222 references are cited.

Sesquiterpenes in grapes and wines: Occurrence, biosynthesis, functionality, and influence of winemaking processes

Grapes are an important global horticultural product, and are mainly used for winemaking. Typically, grapes and wines are rich in various phytochemicals, including phenolics, terpenes, pyrazines, and benzenoids, with different compounds responsible for different nutritional and sensory properties. Among these compounds, sesquiterpenes, a subcategory of the terpenes, are attracting increasing interest as they affect aroma and have potential health benefits. The characteristics of sesquiterpenes in grapes and wines in terms of classification, biosynthesis pathway, and active functions have not been extensively reviewed. This paper summarizes 97 different sesquiterpenes reported in grapes and wines and reviews their biosynthesis pathways and relevant bio-regulation mechanisms. This review further discusses the functionalities of these sesquiterpenes including their aroma contribution to grapes and wines and potential health benefits, as well as how winemaking processes affect sesquiterpene concentrations.

Identification of sesquiterpene synthases from the Basidiomycota Coniophora puteana for the efficient and highly selective β-copaene and cubebol production in E. coli

Background

Terpenes are an important and extremely versatile class of secondary metabolites that are commercially used in the pharmaceutical, food and cosmetics sectors. Genome mining of different fungal collections has revealed the genetic basis for a steadily increasing number of putative terpene synthases without any detailed knowledge about their biochemical properties. The analysis and research of this rich genetic source provides a precious basis for the advancing biotechnological production of an almost endless number of valuable natural metabolites.

Results

Three annotated terpene synthases from the little investigated Basidiomycota Coniophora puteana were studied in this work. For biochemical characterization, the heterologous expression in E. coli was conducted leading to the identification of two sesquiterpene synthases capable of the highly selective generation of β-copaene and cubebol. These compounds are commercially used as food and flavor additives. The new enzymes show the highest reported product selectivity for their main compounds and therefore represent the first exclusive synthases for β-copaene (62% product selectivity) and cubebol (75% product selectivity) generation. In combination with an optimized heterologous microbial production system, we obtained product titers of 215 mg/L β-copaene and 497 mg/L cubebol.

Conclusion

The reported product selectivity and our generated terpene titers exceed all published biotechnological data regarding the production of β-copaene and cubebol. This represents a promising and economic alternative to extraction from natural plant sources and the associated complex product purification.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-1010-z) contains supplementary material, which is available to authorized users.

15-Hydroxygermacranolides as Sources of Structural Diversity: Synthesis of Sesquiterpene Lactones by Cyclization and Rearrangement Reactions. Experimental and DFT Study

A study on the electrophile-induced rearrangement of two 15-hydroxygermacranolides, salonitenolide and artemisiifolin, was carried out. These compounds underwent electrophilic intramolecular cyclizations or acid-mediated rearrangements to give sesquiterpene lactones with different skeletons such as eudesmanolides, guaianolides, amorphanolides, or other germacranolides. The cyclization that gives guaianolides can be considered a biomimetic route to this type of sesquiterpene lactones. The use of acetone as a solvent changes the reactivity of the two starting germacranolides to the acid catalysts, with a 4,15-diol acetonide being the main product obtained. The δ-amorphenolide obtained by intramolecular cyclization of this acetonide is a valuable intermediate for accessing the antimalarials artemisinin and its derivatives. Mechanistic proposals for the transformations are raised, and to provide support them, quantum chemical calculations [DFT B3LYP/6-31+G(d,p) level] were undertaken.