Production of Useful Terpenoids by Higher-Fungus Cell Factory and Synthetic Biology Approaches

Ganoderma tuberculosum Liquid Culture With Vineyard Pruning Extracts for Bioactive Composite Production With Antiproliferative Activity

Ganoderma species have been studied for their pharmacological approaches, such as anticancer, antitumor, antiproliferative, and antioxidant activity. Elicitors are used to increase Ganoderma bioactive composite production. This study aims to evaluate the antiproliferative activity of ethanolic extracts from mycelium of Ganoderma tuberculosum (G. tuberculosum) grown in a liquid medium with vineyard pruning waste (VPW) extracts as elicitors. Ethanolic and aqueous VPW extracts contain resveratrol dimer 4, resveratrol tetramer 1, and naringenin, while toluene and chloroform extracts contain tetradecanoic acid, hexadecanoic acid, and octadecanoic acid. Polar and nonpolar extracts could be promising elicitors for increasing bioactive molecules. Catechin gallate showed the highest correlation (r = 0.66) with biomass. Mycelial ethanolic extracts of G. tuberculosum (native strain from the Sonoran Desert) and Ganoderma lucidum (G. lucidum) (control) were analyzed by ESI-IT-MS, and 27 molecules were identified for the two species. They showed antiproliferative activity against the A549 and C-33 A cell lines but not for ARPE-19. G. tuberculosum culture with VPW had quinic acid, ganodermenonol, ganoderic acid I (GA-I), C2 (GA-C2), and 20-hydroxylucidenic acid P, among others. Molecular docking of ganodermenonol, GA-I, and GA-C2 demonstrates significant interaction with tumor necrotic factor (TNF-α). These ethanolic extracts of Ganoderma are promising sources of bioactive triterpenoids. Their antiproliferative activity did not change between species or treatment. Likewise, the G. tuberculosum and G. lucidum extracts only affected cancer cell lines. This property seems promising for pharmacological applications of these fungal extracts.

Comparative Analysis of Viromes Identified in Multiple Macrofungi

Macrofungi play important roles in the soil elemental cycle of terrestrial ecosystems. Fungal viruses are common in filamentous fungi, and some of them can affect the growth and development of hosts. However, the composition and evolution of macrofungal viruses are understudied. In this study, ninety strains of Trametes versicolor, Coprinellus micaceus, Amanita strobiliformis, and Trametes hirsuta were collected in China. Four mixed pools were generated by combining equal quantities of total RNA from each strain, according to the fungal species, and then subjected to RNA sequencing. The sequences were assembled, annotated, and then used for phylogenetic analysis. Twenty novel viruses or viral fragments were characterized from the four species of macrofungi. Based on the phylogenetic analysis, most of the viral contigs were classified into ten viral families or orders: Barnaviridae, Benyviridae, Botourmiaviridae, Deltaflexiviridae, Fusariviridae, Hypoviridae, Totiviridae, Mitoviridae, Mymonaviridae, and Bunyavirales. Of these, ambi-like viruses with circular genomes were widely distributed among the studied species. Furthermore, the number and overall abundance of viruses in these four species of macrofungi (Basidiomycota) were found to be much lower than those in broad-host phytopathogenic fungi (Ascomycota: Sclerotinia sclerotiorum, and Botrytis cinerea). By employing metatranscriptomic analysis in this study, for the first time, we demonstrated the presence of multiple mycoviruses in Amanita strobiliformis, Coprinellus micaceus, Trametes hirsute, and Trametes versicolor, significantly contributing to research on mycoviruses in macrofungi.

Syncytial Assembly Lines: Consequences of Multinucleate Cellular Compartments for Fungal Protein Synthesis

Fast growth and prodigious cellular outputs make fungi powerful tools in biotechnology. Recent modeling work has exposed efficiency gains associated with dividing the labor of transcription over multiple nuclei, and experimental innovations are opening new windows on the capacities and adaptations that allow nuclei to behave autonomously or in coordination while sharing a single, common cytoplasm. Although the motivation of our review is to motivate and connect recent work toward a greater understanding of fungal factories, we use the analogy of the assembly line as an organizing idea for studying coordinated gene expression, generally.

Biotransformation of triterpenoid ganoderic acids from exogenous diterpene dihydrotanshinone I in the cultures of Ganoderma sessile

BACKGROUND

Triterpenoids have shown a wide range of biological activities including antitumor and antiviral effects. Typically, triterpenes are synthesized through the mevalonate pathway and are extracted from natural plants and fungi. In this work, triterpenoids, ganoderic acids (GAs) were discovered to be produced via biotransformation of a diterpene, 15,16-dihydrotanshinone I (DHT) in the liquid cultured Ganoderma sessile mycelium.

RESULTS

Firstly, the biotransformation products, two rare GAs were isolated and purified by column chromatography, and characterized using HR-ESI-MS spectrometry and NMR spectrometry. The two compounds were Lanosta-7,9(11),24-trien-15α,22,β-diacetoxy-3β-hydroxy-26-oic acid (LTHA) and Lanosta-7,9(11),24-trien-15α,22,β-diacetoxy-3β-carbonyl-26-oic acid (LTCA). Then, transcriptome and proteome technologies were employed to measure the expression of mRNA and protein, which further confirmed that triterpenoid GAs could be transformed from exogenous diterpenoid DHT. At the molecular level, we proposed a hypothesis of the mechanism by which DHT converted to GAs in G. sessile mycelium, and the possible genes involved in biotransformation were verified by RT-qPCR.

CONCLUSIONS

Two rare GAs were obtained and characterized. A biosynthetic pathway of GAs from DHT was proposed. Although the synthetic route was not confirmed, this study provided important insights into omics resources and candidate genes for studying the biotransformation of diterpenes into triterpenes.

Application progress of CRISPR/Cas9 genome-editing technology in edible fungi

Edible fungi are not only delicious but are also rich in nutritional and medicinal value, which is highly sought after by consumers. As the edible fungi industry continues to rapidly advance worldwide, particularly in China, the cultivation of superior and innovative edible fungi strains has become increasingly pivotal. Nevertheless, conventional breeding techniques for edible fungi can be arduous and time-consuming. CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9) is a powerful tool for molecular breeding due to its ability to mediate high-efficiency and high-precision genome modification, which has been successfully applied to many kinds of edible fungi. In this review, we briefly summarized the working mechanism of the CRISPR/Cas9 system and highlighted the application progress of CRISPR/Cas9-mediated genome-editing technology in edible fungi, including Agaricus bisporus, Ganoderma lucidum, Flammulina filiformis, Ustilago maydis, Pleurotus eryngii, Pleurotus ostreatus, Coprinopsis cinerea, Schizophyllum commune, Cordyceps militaris, and Shiraia bambusicola. Additionally, we discussed the limitations and challenges encountered using CRISPR/Cas9 technology in edible fungi and provided potential solutions. Finally, the applications of CRISPR/Cas9 system for molecular breeding of edible fungi in the future are explored.

Unlocking the magic in mycelium: Using synthetic biology to optimize filamentous fungi for biomanufacturing and sustainability

Filamentous fungi drive carbon and nutrient cycling across our global ecosystems, through its interactions with growing and decaying flora and their constituent microbiomes. The remarkable metabolic diversity, secretion ability, and fiber-like mycelial structure that have evolved in filamentous fungi have been increasingly exploited in commercial operations. The industrial potential of mycelial fermentation ranges from the discovery and bioproduction of enzymes and bioactive compounds, the decarbonization of food and material production, to environmental remediation and enhanced agricultural production. Despite its fundamental impact in ecology and biotechnology, molds and mushrooms have not, to-date, significantly intersected with synthetic biology in ways comparable to other industrial cell factories (e.g. Escherichia coli,Saccharomyces cerevisiae, and Komagataella phaffii). In this review, we summarize a suite of synthetic biology and computational tools for the mining, engineering and optimization of filamentous fungi as a bioproduction chassis. A combination of methods across genetic engineering, mutagenesis, experimental evolution, and computational modeling can be used to address strain development bottlenecks in established and emerging industries. These include slow mycelium growth rate, low production yields, non-optimal growth in alternative feedstocks, and difficulties in downstream purification. In the scope of biomanufacturing, we then detail previous efforts in improving key bottlenecks by targeting protein processing and secretion pathways, hyphae morphogenesis, and transcriptional control. Bringing synthetic biology practices into the hidden world of molds and mushrooms will serve to expand the limited panel of host organisms that allow for commercially-feasible and environmentally-sustainable bioproduction of enzymes, chemicals, therapeutics, foods, and materials of the future.

Genome, transcriptome, and metabolome analyses provide new insights into the resource development in an edible fungus Dictyophora indusiata

Dictyophora indusiata (Vent. Ex Pers.) Fisch. (DI) is an edible and medicinal fungus widely used in East Asian countries. However, during DI cultivation, the formation of fruiting bodies cannot be regulated, which leads to yield and quality losses. The present study performed a combined genome, transcriptome, and metabolome analysis of DI. Using Nanopore and Illumina sequencing approaches, we created the DI reference genome, which was 67.32 Mb long with 323 contigs. We identified 19,909 coding genes on this genome, of which 46 gene clusters were related to terpenoid synthesis. Subsequent transcriptome sequencing using five DI tissues (cap, indusia, mycelia, stipe, and volva) showed high expression levels of genes in the cap, indicating the tissue's importance in regulating the fruiting body formation. Meanwhile, the metabolome analysis identified 728 metabolites from the five tissues. Mycelium was rich in choline, while volva was rich in dendronobilin; stipe had monosaccharides as the primary component, and the cap was the main source of indole acetic acid (IAA) synthesis. We confirmed the importance of tryptophan metabolism for DI fruiting body differentiation based on KEGG pathway analysis. Finally, the combined multiomics analysis identified three new genes related to IAA synthesis of the tryptophan metabolic pathway in the cap, which may regulate DI fruiting body synthesis and improve DI quality. Thus, the study's findings expand our understanding of resource development and the molecular mechanisms underlying DI development and differentiation. However, the current genome is still a rough draft that needs to be strengthened.

Engineering fungal terpene biosynthesis

Covering: 2015 to 2022Fungal terpenoids are of large structural diversity and often exhibit interesting biological activities. Recent work has focused on two main aspects: (1) the discovery and understanding of unknown biosynthetic genes and pathways, and (2) the usage of already known biosynthetic genes in the construction of high yielding production strains. Both aspects will be covered in this review article that aims to summarise the most important work of the past few years.

Increasing the production of the bioactive compounds in medicinal mushrooms: an omics perspective

Macroscopic fungi, mainly higher basidiomycetes and some ascomycetes, are considered medicinal mushrooms and have long been used in different areas due to their pharmaceutically/nutritionally valuable bioactive compounds. However, the low production of these bioactive metabolites considerably limits the utilization of medicinal mushrooms both in commerce and clinical trials. As a result, many attempts, ranging from conventional methods to novel approaches, have been made to improve their production. The novel strategies include conducting omics investigations, constructing genome-scale metabolic models, and metabolic engineering. So far, genomics and the combined use of different omics studies are the most utilized omics analyses in medicinal mushroom research (both with 31% contribution), while metabolomics (with 4% contribution) is the least. This article is the first attempt for reviewing omics investigations in medicinal mushrooms with the ultimate aim of bioactive compound overproduction. In this regard, the role of these studies and systems biology in elucidating biosynthetic pathways of bioactive compounds and their contribution to metabolic engineering will be highlighted. Also, limitations of omics investigations and strategies for overcoming them will be provided in order to facilitate the overproduction of valuable bioactive metabolites in these valuable organisms.

Biosynthesis of mushroom-derived type II ganoderic acids by engineered yeast

Type II ganoderic acids (GAs) produced by the traditional medicinal mushroom Ganoderma are a group of triterpenoids with superior biological activities. However, challenges in the genetic manipulation of the native producer, low level of accumulation in the farmed mushroom, the vulnerabilities of the farming-based supply chain, and the elusive biosynthetic pathway have hindered the efficient production of type II GAs. Here, we assemble the genome of type II GAs accumulating G. lucidum accession, screen cytochrome P450 enzymes (CYPs) identified from G. lucidum in baker's yeast, identify key missing CYPs involved in type II GAs biosynthesis, and investigate the catalytic reaction sequence of a promiscuous CYP. Then, we engineer baker's yeast for bioproduciton of GA-Y (3) and GA-Jb (4) and achieve their production at higher level than those from the farmed mushroom. Our findings facilitate the further deconvolution of the complex GA biosynthetic network and the development of microbial cell factories for producing GAs at commercial scale.

The Aspartic Protease Yps3p and Cell Wall Glucanase Scw10p Are Novel Determinants That Enhance the Secretion of the Antitumor Triterpenoid GA-HLDOA in Saccharomyces cerevisiae

Efficient bioproduction of triterpenoids is gaining increasing interest because of their significant biological applications; however, the secretion and bioproduction of triterpenoids are hindered by untapped genetic determinants. In our previous study, we observed that different engineered Saccharomyces cerevisiae strains exhibit different abilities for secreting the antitumor triterpenoid ganoderic acid 3-hydroxy-lanosta-8,24-dien-26-oic acid (GA-HLDOA). In the present study, we performed comparative proteomics analyses of the engineered strains and identified two genes, encoding an aspartic protease, YPS3, and a cell wall glucanase, SCW10, as the most effective determinants that enhance the secretion of GA-HLDOA. Compared with this control strain, strain BJ5464-r demonstrated an overexpression of YPS3 and SCW10 resulting in 3.9-fold and 4.7-fold higher secretion of GA-HLDOA, respectively, and these increases were accompanied by an increase in cell permeability. Moreover, compared with the YPS3-overexpressing strain, the SCW10-overexpressing strain had a thinner outer mannan layer. Our findings offer valuable insights into designing microbial cell factories for the efficient secretion of triterpenoids.

Optimization of the production process for the anticancer lead compound illudin M: process development in stirred tank bioreactors

BACKGROUND

The fungal natural products illudin S and M have been investigated as precursors for the development of semisynthetic anticancer agents such as Irofulven (illudin S derivative) which is currently in phase II clinical trials. Recently, illudin M derivatives have shown improved in vitro selectivity towards cancer cells encouraging further investigation. This requires a stable supply of the precursor which is produced by Basidiomycota of the genus Omphalotus. We have recently reported a robust shake flask process for the production of gram quantities of illudin M from Omphalotus nidiformis aiming to transfer that process into stirred tank bioreactors, which can be used in a commercial production set-up. However, process transfer across different systems is not straightforward and particularly challenging when the producer is morphologically complex. There are only a few reports that address the development of bioprocesses for the production of compounds from Basidiomycota as these organisms have not been extensively studied because of their complex life cycles and often are difficult to cultivate under laboratory conditions.

RESULTS

The recently developed shake flask process delivering stable titers of ~ 940 mg L-1 of illudin M was investigated using off-gas analysis to identify critical parameters which facilitated the transfer from shaken into stirred tank bioreactors. Comparable titers to the shake flask process were achieved in 2 L stirred tank bioreactors (1.5 L working volume) by controlling growth of biomass with a carefully timed pH-shift combined with an improved precursor-feeding strategy. A scale-up experiment in a 15 L bioreactor (10 L working volume), resembling the process at 1.5 L resulted in 523 mg L-1 and is the starting point for optimization of the identified parameters at that scale.

CONCLUSION

By identifying and controlling key process parameters, the production process for illudin M was transferred from shake flasks into 2 L stirred tank bioreactors reaching a comparable titer (> 900 mg L-1), which is significantly higher than any previously reported. The insights obtained from 10 L scale pave the way towards further scale-up studies that will enable a sustainable supply of illudin M to support preclinical and clinical development programs.

Effects of Oleic Acid Addition Methods on the Metabolic Flux Distribution of Ganoderic Acids R, S and T's Biosynthesis

The effects of oleic acid addition methods on the metabolic flux distribution of ganoderic acids R, S and T's biosynthesis from Ganoderma lucidum were investigated. The results showed that adding filter-sterilized oleic acid in the process of submerged fermentation and static culture is of benefit to the synthesis of ganoderic acids R, S and T. The metabolic fluxes were increased by 97.48%, 78.42% and 43.39%, respectively. The content of ganoderic acids R, S and T were 3.11 times, 5.19 times and 1.44 times higher, respectively, than they were in the control group, which was without additional oleic acid. Ganoderic acids R, S and T's synthesis pathways (GAP), tricarboxylic acid cycles (TCA), pentose phosphate pathways (PP) and glycolysis pathways (EMP) were all enhanced in the process. Therefore, additional oleic acid can strengthen the overall metabolic flux distribution of G. lucidum in a submerged fermentation-static culture and it can reduce the accumulation of the by-product mycosterol. This study has laid an important foundation for improving the production of triterpenes in the submerged fermentation of G. lucidum.

Progress in biological activities and biosynthesis of edible fungi terpenoids

The edible fungi have both edible and medicinal functions, in which terpenoids are one of the most important active ingredients. Terpenoids possess a wide range of biological activities and show great potential in the pharmaceutical and healthcare industries. In this review, the diverse biological activities of edible fungi terpenoids were summarized with emphasis on the mechanism of anti-cancer and anti-inflammation. Subsequently, this review focuses on advances in knowledge and understanding of the biosynthesis of terpenoids in edible fungi, especially in the generation of sesquiterpenes, diterpenes, and triterpenes. This paper is aim to provide an overview of biological functions and biosynthesis developed for utilizing the terpenoids in edible fungi.

Hybrid Assembly Improves Genome Quality and Completeness of Trametes villosa CCMB561 and Reveals a Huge Potential for Lignocellulose Breakdown

Trametes villosa is a wood-decaying fungus with great potential to be used in the bioconversion of agro-industrial residues and to obtain high-value-added products, such as biofuels. Nonetheless, the lack of high-quality genomic data hampers studies investigating genetic mechanisms and metabolic pathways in T. villosa, hindering its application in industry. Herein, applying a hybrid assembly pipeline using short reads (Illumina HiSeq) and long reads (Oxford Nanopore MinION), we obtained a high-quality genome for the T. villosa CCMB561 and investigated its genetic potential for lignocellulose breakdown. The new genome possesses 143 contigs, N50 of 1,009,271 bp, a total length of 46,748,415 bp, 14,540 protein-coding genes, 22 secondary metabolite gene clusters, and 426 genes encoding Carbohydrate-Active enzymes. Our CAZome annotation and comparative genomic analyses of nine Trametes spp. genomes revealed T. villosa CCMB561 as the species with the highest number of genes encoding lignin-modifying enzymes and a wide array of genes encoding proteins for the breakdown of cellulose, hemicellulose, and pectin. These results bring to light the potential of this isolate to be applied in the bioconversion of lignocellulose and will support future studies on the expression, regulation, and evolution of genes, proteins, and metabolic pathways regarding the bioconversion of lignocellulosic residues.

Biosynthesis of a novel ganoderic acid by expressing CYP genes from Ganoderma lucidum in Saccharomyces cerevisiae

Ganoderic acids (GAs), a group of highly oxygenated lanostane-type triterpenoids from the traditional Chinese medicinal mushroom Ganoderma lucidum, possessed significant pharmacological activities. Due to the difficulty in its genetic manipulation, low yield, and slow growth of G. lucidum, biosynthesis of GAs in a heterologous host is a promising alternative for their efficient production. Heterologous production of a GA, 3-hydroxy-lanosta-8,24-dien-26-oic acid (HLDOA), was recently achieved by expressing CYP5150L8 from Ganoderma lucidum in Saccharomyces cerevisiae, but post-modification of HLDOA to biosynthesize other GAs remains unclear. In this study, another P450 from G. lucidum, CYP5139G1, was identified to be responsible for C-28 oxidation of HLDOA, resulting in the formation of a new GA 3,28-dihydroxy-lanosta-8,24-dien-26-oic acid (DHLDOA) by the engineered yeast, whose chemical structure was confirmed by UPLC-APCI-HRMS and NMR. In vitro enzymatic experiments confirmed the oxidation of HLDOA to DHLDOA by CYP5139G1. As the DHLDOA production was low (0.27 mg/L), to improve it, the strategy of adjusting the dosage of hygromycin and geneticin G418 to respectively manipulate the copy number of plasmids pRS425-Hyg-CYP5150L8-iGLCPR (harboring CYP5150L8, iGLCPR, and hygromycin-resistant gene hygR) and pRS426-KanMx-CYP5139G1 (harboring CYP5139G1 and G418-resistant gene KanMx) was adopted. Finally, 2.2 mg/L of DHLDOA was obtained, which was 8.2 fold of the control (without antibiotics addition). The work enriches the GA biosynthetic enzyme library, and is helpful to construct heterologous cell factories for other GA production as well as to elucidate the authentic GA biosynthetic pathway in G. lucidum. KEY POINTS: • Another P450 gene responsible for GA's post-modification was discovered and identified. • One new GA, DHLDOA, was identified and produced via engineered yeast. • With the balance of the two CYP genes expression, DHLDOA production was significantly improved.

Biosynthesis and regulation of terpenoids from basidiomycetes: exploration of new research

Basidiomycetes, also known as club fungi, consist of a specific group of fungi. Basidiomycetes produce a large number of secondary metabolites, of which sesquiterpenoids, diterpenoids and triterpenoids are the primary components. However, these terpenoids tend to be present in low amounts, which makes it difficult to meet application requirements. Terpenoid biosynthesis improves the quantity of these secondary metabolites. However, current understanding of the biosynthetic mechanism of terpenoids in basidiomycetes is insufficient. Therefore, this article reviews the latest research on the biosynthesis of terpenoids in basidiomycetes and summarizes the CYP450 involved in the biosynthesis of terpenoids in basidiomycetes. We also propose opportunities and challenges for chassis microbial heterologous production of terpenoids in basidiomycetes and provide a reference basis for the better development of basidiomycete engineering.

Advances in production and structural derivatization of the promising molecule ursolic acid

Ursolic acid (UA) is a ursane-type pentacyclic triterpenoid compound, naturally produced in plants via specialized metabolism and exhibits vast range of remarkable physiological activities and pharmacological manifestations. Owing to significant safety and efficacy in different medical conditions, UA may serve as a backbone to produce its derivatives with novel therapeutic functions. This review aims to provide ideas for exploring more diverse structures to improve UA pharmacological activity and increasing its biological yield to meet the industrial requirements by systematically reviewing the current research progress of UA. We first provides an overview of the pharmacological activities, acquisition methods and structural modifications of UA. Among them, we focused on the synthetic modifications of UA to yield valuable derivatives with enhanced therapeutic potential. Furthermore, harnessing the essential advances for green synthesis of UA and its derivatives by advent of metabolic engineering and synthetic biology are of great concern. In this regard, all pivotal advances for enhancing the production of UA have been discussed. In combination with the advantages of UA biosynthesis and transformation strategy, large-scale microbial production of UA is a promising platform for further exploration.

Time-scale dynamics of proteome predicts the central carbon metabolism involved in triterpenoid accumulation responsive to nitrogen limitation in Ganoderma lucidum

Central carbon metabolism describes the integration of transport pathway of main carbon sources inside the cell. Nitrogen (N) limitation is a favorable approach to stimulate ganoderic triterpenoid (GT) accumulation in Ganoderma lucidum. In this study, the dynamic regulation of metabolism reassignment towards GT biosynthesis responsive to N limitation was investigated by iTRAQ-based proteome. Physiological data suggested that N limitation slightly affected cell growth but significantly enhanced GT contents in the initial 20 days. From day 10, the protein contents were halted by prolonged N limitation duration. Proteomics-based investigations revealed that the carbon skeletons integrated into GT precursors were regenerated by glycolysis and the tricarboxylic acid (TCA) cycle. Cells strategically reserved nitrogen by barely incorporating it into TCA cycle intermediates to form amino acids, and enzymes involved in protein degradation were up regulated. Furthermore, regulation of proteins in response to abiotic stress and oxidation- reduction processes played a critical role in maintaining cellular homeostasis. These findings indicated that the flux of carbon into GT following N deficiency was a consequence of the remodeling of intermediate metabolism in TCA cycle and glycolysis reactions. This study provides a rationale for genetic engineering of G. lucidum, which may enable synchronized biomass and GT synthesis.

Ustilago maydis Serves as a Novel Production Host for the Synthesis of Plant and Fungal Sesquiterpenoids

Sesquiterpenoids are important secondary metabolites with various pharma- and nutraceutical properties. In particular, higher basidiomycetes possess a versatile biosynthetic repertoire for these bioactive compounds. To date, only a few microbial production systems for fungal sesquiterpenoids have been established. Here, we introduce Ustilago maydis as a novel production host. This model fungus is a close relative of higher basidiomycetes. It offers the advantage of metabolic compatibility and potential tolerance for substances toxic to other microorganisms. We successfully implemented a heterologous pathway to produce the carotenoid lycopene that served as a straightforward read-out for precursor pathway engineering. Overexpressing genes encoding enzymes of the mevalonate pathway resulted in increased lycopene levels. Verifying the subcellular localization of the relevant enzymes revealed that initial metabolic reactions might take place in peroxisomes: despite the absence of a canonical peroxisomal targeting sequence, acetyl-CoA C-acetyltransferase Aat1 localized to peroxisomes. By expressing the plant (+)-valencene synthase CnVS and the basidiomycete sesquiterpenoid synthase Cop6, we succeeded in producing (+)-valencene and α-cuprenene, respectively. Importantly, the fungal compound yielded about tenfold higher titers in comparison to the plant substance. This proof of principle demonstrates that U. maydis can serve as promising novel chassis for the production of terpenoids.

Cyclodextrins facilitate the efficient secretion of an anti-tumor triterpenoid ganoderic acid HLDOA by Saccharomyces cerevisiae

As a large group of natural product with significant biological activities, triterpenoid secretion is of particular importance towards its bioproduction. Due to the lack of specific transporters, most triterpenoids are naturally accumulated inside the cells. In this study, by taking an antitumor triterpenoid ganoderic acid 3-hydroxy-lanosta-8,24-dien-26 oic acid (GA-HLDOA) as example, we discovered that addition of 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) or 2,6-dimethyl-β-cyclodextrin (DM-β-CD) enable the fast and sufficient secretion of GA-HLDOA by the recombinant Saccharomyces cerevisiae strain as constructed in our previous study. In addition, these cyclodextrins (CDs) could not enter into cells, while no significant change of the cell membrane fluidity was observed after CDs treatment. This discovery provides a potential generally applicable method for triterpenoid secretion.

CRISPR-Cas9 assisted functional gene editing in the mushroom Ganoderma lucidum

The genetic manipulation of basidiomycete mushrooms is notoriously difficult and immature, and there is a lack of research reports on clustered regularly interspaced short palindromic repeat (CRISPR) based gene editing of functional genes in mushrooms. In this work, Ganoderma lucidum, a famous traditional medicinal basidiomycete mushroom, which produces a type of unique triterpenoid-anti-tumor ganoderic acids (GAs), was used, and a CRISPR/CRISPR-associated protein-9 nuclease (Cas9) editing system for functional genes of GA biosynthesis was constructed in the mushroom. As proof of concept, the effect of different gRNA constructs with endogenous u6 promoter and self-cleaving ribozyme HDV on ura3 disruption efficiency was investigated at first. The established system was applied to edit a cytochrome P450 monooxygenase (CYP450) gene cyp5150l8, which is responsible for a three-step biotransformation of lanosterol at C-26 to ganoderic acid 3-hydroxy-lanosta-8, 24-dien-26 oic acid. As a result, precisely edited cyp5150l8 disruptants were obtained after sequencing confirmation. The fermentation products of the wild type (WT) and cyp5150l8 disruptant were analyzed, and a significant decrease in the titer of four identified GAs was found in the mutant compared to WT. Another CYP gene involved in the biosynthesis of squalene-type triterpenoid 2, 3; 22, 23-squalene dioxide, cyp505d13, was also disrupted using the established CRISPR-Cas9 based gene editing platform of G. lucidum. The work will be helpful to strain molecular breeding and biotechnological applications of G. lucidum and other basidiomycete mushrooms.

Combining transcriptomics and metabolomics to reveal the underlying molecular mechanism of ergosterol biosynthesis during the fruiting process of Flammulina velutipes

Background

Flammulina velutipes has been recognized as a useful basidiomycete with nutritional and medicinal values. Ergosterol, one of the main sterols of F. velutipes is an important precursor of novel anticancer and anti-HIV drugs. Therefore, many studies have focused on the biosynthesis of ergosterol and have attempted to upregulate its content in multiple organisms. Great progress has been made in understanding the regulation of ergosterol biosynthesis in Saccharomyces cerevisiae. However, this molecular mechanism in F. velutipes remains largely uncharacterized.

Results

In this study, nine cDNA libraries, prepared from mycelia, young fruiting bodies and mature fruiting bodies of F. velutipes (three replicate sets for each stage), were sequenced using the Illumina HiSeq™ 4000 platform, resulting in at least 6.63 Gb of clean reads from each library. We studied the changes in genes and metabolites in the ergosterol biosynthesis pathway of F. velutipes during the development of fruiting bodies. A total of 13 genes (6 upregulated and 7 downregulated) were differentially expressed during the development from mycelia to young fruiting bodies (T1), while only 1 gene (1 downregulated) was differentially expressed during the development from young fruiting bodies to mature fruiting bodies (T2). A total of 7 metabolites (3 increased and 4 reduced) were found to have changed in content during T1, and 4 metabolites (4 increased) were found to be different during T2. A conjoint analysis of the genome-wide connection network revealed that the metabolites that were more likely to be regulated were primarily in the post-squalene pathway.

Conclusions

This study provides useful information for understanding the regulation of ergosterol biosynthesis and the regulatory relationship between metabolites and genes in the ergosterol biosynthesis pathway during the development of fruiting bodies in F. velutipes.

Unusual and Highly Bioactive Sesterterpenes Synthesized by Pleurotus ostreatus during Coculture with Trametes robiniophila Murr

Candida albicans and Cryptococcus neoformans, human-pathogenic fungi found worldwide, are receiving increasing attention due to high morbidity and mortality in immunocompromised patients. In the present work, 110 fungus pairs were constructed by coculturing 16 wood-decaying basidiomycetes, among which coculture of Trametes robiniophila Murr and Pleurotus ostreatus was found to strongly inhibit pathogenic fungi through bioactivity-guided assays. A combination of metabolomics and molecular network analysis revealed that 44 features were either newly synthesized or produced at high levels in this coculture system and that 6 of the features that belonged to a family of novel and unusual linear sesterterpenes contributed to high activity with MICs of 1 to 32 μg/ml against pathogenic fungi. Furthermore, dynamic ¹³C-labeling analysis revealed an association between induced features and the corresponding fungi. Unusual sesterterpenes were ¹³C labeled only in P. ostreatus in a time course after stimulation by the coculture, suggesting that these sesterterpenes were synthesized by P. ostreatus instead of T. robiniophila Murr. Sesterterpene compounds 1 to 3 were renamed postrediene A to C. Real-time reverse transcription-quantitative PCR (RT-qPCR) analysis revealed that transcriptional levels of three genes encoding terpene synthase, farnesyl-diphosphate farnesyltransferase, and oxidase were found to be 8.2-fold, 88.7-fold, and 21.6-fold higher, respectively, in the coculture than in the monoculture, indicating that biosynthetic gene cluster 10 was most likely responsible for the synthesis of these sesterterpenes. A putative biosynthetic pathway of postrediene A to postrediene C was then proposed based on structures of sesterterpenes and molecular network analysis.IMPORTANCE A number of gene clusters involved in biosynthesis of secondary metabolites are presumably silent or expressed at low levels under conditions of standard laboratory cultivation, resulting in a large gap between the pool of discovered metabolites and genome capability. This work mimicked naturally occurring competition by construction of an artificial coculture of basidiomycete fungi for the identification of secondary metabolites with novel scaffolds and excellent bioactivity. Unusual linear sesterterpenes of postrediene A to C synthesized by P. ostreatus not only were promising lead drugs against human-pathogenic fungi but also highlighted a distinct pathway for sesterterpene biosynthesis in basidiomycetes. The current work provides an important basis for uncovering novel gene functions involved in sesterterpene synthesis and for gaining insights into the mechanism of silent gene activation in fungal defense.

Cell Factory Engineering

Rational approaches to modifying cells to make molecules of interest are of substantial economic and scientific interest. Most of these efforts aim at the production of native metabolites, expression of heterologous biosynthetic pathways, or protein expression. Reviews of these topics have largely focused on individual strategies or cell types, but collectively they fall under the broad umbrella of a growing field known as cell factory engineering. Here we condense >130 reviews and key studies in the art into a meta-review of cell factory engineering. We identified 33 generic strategies in the field, all applicable to multiple types of cells and products, and proven successful in multiple major cell types. These apply to three major categories: production of native metabolites and/or bioactives, heterologous expression of biosynthetic pathways, and protein expression. This meta-review provides general strategy guides for the broad range of applications of rational engineering of cell factories.

Increased production of ganoderic acids by overexpression of homologous farnesyl diphosphate synthase and kinetic modeling of ganoderic acid production in Ganoderma lucidum

Background

Ganoderic acids (GAs), derived from the medicinal mushroom Ganoderma lucidum, possess anticancer and other important pharmacological activities. To improve production of GAs, a homologous farnesyl diphosphate synthase (FPS) gene was overexpressed in G. lucidum. Moreover, the influence of FPS gene overexpression on GA production was investigated by developing the corresponding mathematical models.

Results

The maximum levels of total GAs and individual GAs (GA-T, GA-S, and GA-Me) in the transgenic strain were 2.76 mg/100 mg dry weight (DW), 41 ± 2, 21 ± 5, and 28 ± 1 μg/100 mg DW, respectively, which were increased by 2.28-, 2.27-, 2.62-, and 2.80-folds compared with those in the control. Transcription levels of squalene synthase (SQS) and lanosterol synthase (LS) genes during GA biosynthesis were upregulated by 2.28- and 1.73-folds, respectively, in the transgenic G. lucidum. In addition, the developed unstructured models had a satisfactory fit for the process of GA production in submerged cultures of G. lucidum. Analysis of the kinetic process showed that FPS gene overexpression had a stronger positive impact on GA production compared with its influence on cell growth. Also, FPS gene overexpression led to a higher non-growth-associated-constant β (1.151) over the growth-associated-constant α (0.026) in the developed models.

Conclusions

FPS gene overexpression is an effective strategy to improve the production of GAs in G. lucidum. The developed mathematical models are useful for developing a better GA production process in future large-scale bioreactors.

Electronic supplementary material

The online version of this article (10.1186/s12934-019-1164-3) contains supplementary material, which is available to authorized users.

Interdependent nitric oxide and hydrogen peroxide independently regulate the coix seed oil-induced triterpene acid accumulation in Ganoderma lingzhi

Recent progress has been made in adding exogenous vegetable oils in culture media to promote bioactive metabolite production in several medicinal mushrooms, but the mechanism is still unclear. In this study, we found that the vegetable oil coix seed oil (CSO) could induce the biosynthesis of triterpene acids (TAs) and also significantly increase cytoplasmic nitric oxide (NO) and hydrogen peroxide (H₂O₂) concentrations in the mycelium of Ganoderma lingzhi. The change in TA biosynthesis caused by CSO could be reversed by adding NO scavenger or H₂O₂ scavenger, and adding NO scavenger or H₂O₂ scavenger resulted in the reduction of the cytoplasmic H₂O₂ or NO concentration under CSO treatment, respectively. Moreover, adding NO scavenger or H₂O₂ scavenger reversed TA biosynthesis, which could be rescued by H₂O₂ or NO donor, respectively. Taken together, our study indicated that both NO and H₂O₂ were involved in the regulation of TA biosynthesis, and CSO-activated NO and H₂O₂ were interdependent but independently regulated the TA biosynthesis under CSO treatment in G. lingzhi.

Improving lupeol production in yeast by recruiting pathway genes from different organisms

Lupeol is a pentacyclic triterpene that shows a variety of pharmacological properties. Compared to engineering the production of sesquiterpenes and diterpenes, it is much more challenging to engineer the biosynthesis of triterpenes in microbial platforms. This study showed our efforts on engineering the triterpene pathway in Escherichia coli and Saccharomyces cerevisiae cells by recruiting the codon-optimized three lupeol pathway genes from different organisms. By comparing their activities with their respective counterparts, the squalene synthase from Thermosynechococcus elongates (tSQS), the squalene epoxidase from Rattus norvegicus (rSE) and the lupeol synthase from Olea europaea (OeLUP) were introduced into E. coli BL21(DE3), a break-through from zero was observed for lupeol biosynthesis in a prokaryotic host. We also assessed the lupeol pathway under two different yeast backgrounds-WAT11 and EPY300, and have found that the engineered strains based on EPY300, named ECHHOe, processed the best lupeol-producing ability with the maximum lupeol titer being 200.1 mg l⁻¹ at 30 °C in a 72 h-flask culture, which so far was the highest amount of lupeol obtained by a microbial system and provides a basis for further industrial application of lupeol in the future.

Biological and chemical diversity go hand in hand: Basidiomycota as source of new pharmaceuticals and agrochemicals

The Basidiomycota constitutes the second largest higher taxonomic group of the Fungi after the Ascomycota and comprises over 30.000 species. Mycelial cultures of Basidiomycota have already been studied since the 1950s for production of antibiotics and other beneficial secondary metabolites. Despite the fact that unique and selective compounds like pleuromutilin were obtained early on, it took several decades more until they were subjected to a systematic screening for antimicrobial and anticancer activities. These efforts led to the discovery of the strobilurins and several hundreds of further compounds that mainly constitute terpenoids. In parallel the traditional medicinal mushrooms of Asia were also studied intensively for metabolite production, aimed at finding new therapeutic agents for treatment of various diseases including metabolic disorders and the central nervous system. While the evaluation of this organism group has in general been more tedious as compared to the Ascomycota, the chances to discover new metabolites and to develop them further to candidates for drugs, agrochemicals and other products for the Life Science industry have substantially increased over the past decade. This is owing to the revolutionary developments in -OMICS techniques, bioinformatics, analytical chemistry and biotechnological process technology, which are steadily being developed further. On the other hand, the new developments in polythetic fungal taxonomy now also allow a more concise selection of previously untapped organisms. The current review is dedicated to summarize the state of the art and to give an outlook to further developments.

Biosynthesis of bioactive natural products from Basidiomycota

The club fungi, Basidioycota, produce a wide range of bioactive compounds. Here, we describe recent studies on the biosynthetic pathways and enzymes of bioactive natural products from these fungi.

Multi-omics data-driven investigations of metabolic diversity of plant triterpenoids

The vast majority of structurally diverse metabolites play essential roles in mediating the interactions between plant and environment, and constitute a valuable resource for industrial applications. Recent breakthroughs in sequencing technology have greatly accelerated metabolic studies of natural plant products, providing opportunities to investigate the molecular basis underlying the diversity of specialized plant metabolites through large-scale analysis. Here, we focus on the biosynthesis of plant triterpenoids, especially the three diversifying reactions (cyclization, oxidation and glycosylation) that largely contribute to the structural diversity of triterpenoids. Gene mining through large-scale omics data and functional characterization of metabolic genes including enzymes, transcription factors and transporters could provide important insights into the evolution of specialized plant metabolism and pave the way for the production of high-value metabolites or derivatives using synthetic biology approaches.

Discovery and Engineering of Cytochrome P450s for Terpenoid Biosynthesis

Terpenoids represent 60% of known natural products, including many drugs and drug candidates, and their biosynthesis is attracting great interest. However, the unknown cytochrome P450s (CYPs) in terpenoid biosynthetic pathways make the heterologous production of related terpenoids impossible, while the slow kinetics of some known CYPs greatly limit the efficiency of terpenoid biosynthesis. Thus, there is a compelling need to discover and engineer CYPs for terpenoid biosynthesis to fully realize their great potential for industrial application. This review article summarizes the current state of CYP discovery and engineering in terpenoid biosynthesis, focusing on recent synthetic biology approaches toward prototyping CYPs in heterologous hosts. We also propose several strategies for further accelerating CYP discovery and engineering.

Implication of Fusarium graminearum primary metabolism in its resistance to benzimidazole fungicides as revealed by 1H NMR metabolomics

Fungal metabolomics is a field of high potential but yet largely unexploited. Focusing on plant-pathogenic fungi, no metabolomics studies exist on their resistance to fungicides, which represents a major issue that the agrochemical and agricultural sectors are facing. Fungal infections cause quantitative, but also qualitative yield losses, especially in the case of mycotoxin-producing species. The aim of the study was to correlate metabolic changes in Fusarium graminearum strains' metabolomes with their carbendazim-resistant level and discover corresponding metabolites-biomarkers, with primary focus on its primary metabolism. For this purpose, comparative ¹H NMR metabolomics was applied to a wild-type and four carbendazim-resistant Fusarium graminearum strains following or not exposure to the fungicide. Results showed an excellent discrimination between the strains based on their carbendazim-resistance following exposure to low concentration of the fungicide (2 mg L^-1). Both genotype and fungicide treatments had a major impact on fungal metabolism. Among the signatory metabolites, a positive correlation was discovered between the content of F. graminearum strains in amino acids of the aromatic and pyruvate families, l-glutamate, l-proline, l-serine, pyroglutamate, and succinate and their carbendazim-resistance level. In contrary, their content in l-glutamine and l-threonine, had a negative correlation. Many of these metabolites play important roles in fungal physiology and responses to stresses. This work represents a proof-of-concept of the applicability of ¹H NMR metabolomics for high-throughput screening of fungal mutations leading to fungicide resistance, and the study of its biochemical basis, focusing on the involvement of primary metabolism. Results could be further exploited in programs of resistance monitoring, genetic engineering, and crop protection for combating fungal resistance to fungicides.

Comprehensive Secondary Metabolite Profiling Toward Delineating the Solid and Submerged-State Fermentation of Aspergillus oryzae KCCM 12698

Aspergillus oryzae has been commonly used to make koji, meju, and soy sauce in traditional food fermentation industries. However, the metabolic behaviors of A. oryzae during fermentation in various culture environments are largely uncharacterized. Thus, we performed time resolved (0, 4, 8, 12, 16 day) secondary metabolite profiling for A. oryzae KCCM 12698 cultivated on malt extract agar and broth (MEA and MEB) under solid-state fermentation (SSF) and submerged fermentation (SmF) conditions using the ultrahigh performance liquid chromatography-linear trap quadrupole-ion trap-mass spectrometry (UHPLC-LTQ-IT-MS/MS) followed by multivariate analyses. We observed the relatively higher proportions of coumarins and oxylipins in SSF, whereas the terpenoids were abundant in SmF. Moreover, we investigated the antimicrobial efficacy of metabolites that were extracted from SSF and SmF. The SSF extracts showed higher antimicrobial activities as compared to SmF, with higher production rates of bioactive secondary metabolites viz., ketone-citreoisocoumarin, pentahydroxy-anthraquinone, hexylitaconic acid, oxylipins, and saturated fatty acids. The current study provides the underpinnings of a metabolomic framework regarding the growth and bioactive compound production for A. oryzae under the primarily employed industrial cultivation states. Furthermore, the study holds the potentials for rapid screening and MS-characterization of metabolites helpful in determining the consumer safety implications of fermented foods involving Koji mold.

Engineering Mycorrhizal Symbioses to Alter Plant Metabolism and Improve Crop Health

Creating sustainable bioeconomies for the 21st century relies on optimizing the use of biological resources to improve agricultural productivity and create new products. Arbuscular mycorrhizae (phylum Glomeromycota) form symbiotic relationships with over 80% of vascular plants. In return for carbon, these fungi improve plant health and tolerance to environmental stress. This symbiosis is over 400 million years old and there are currently over 200 known arbuscular mycorrhizae, with dozens of new species described annually. Metagenomic sequencing of native soil communities, from species-rich meadows to mangroves, suggests biologically diverse habitats support a variety of mycorrhizal species with potential agricultural, medical, and biotechnological applications. This review looks at the effect of mycorrhizae on plant metabolism and how we can harness this symbiosis to improve crop health. I will first describe the mechanisms that underlie this symbiosis and what physiological, metabolic, and environmental factors trigger these plant-fungal relationships. These include mycorrhizal manipulation of host genetic expression, host mitochondrial and plastid proliferation, and increased production of terpenoids and jasmonic acid by the host plant. I will then discuss the effects of mycorrhizae on plant root and foliar secondary metabolism. I subsequently outline how mycorrhizae induce three key benefits in crops: defense against pathogen and herbivore attack, drought resistance, and heavy metal tolerance. I conclude with an overview of current efforts to harness mycorrhizal diversity to improve crop health through customized inoculum. I argue future research should embrace synthetic biology to create mycorrhizal chasses with improved symbiotic abilities and potentially novel functions to improve plant health. As the effects of climate change and anthropogenic disturbance increase, the global diversity of arbuscular mycorrhizal fungi should be monitored and protected to ensure this important agricultural and biotechnological resource for the future.

The Genome of Medicinal Plant Macleaya cordata Provides New Insights into Benzylisoquinoline Alkaloids Metabolism

The overuse of antibiotics in animal agriculture and medicine has caused a series of potential threats to public health. Macleaya cordata is a medicinal plant species from the Papaveraceae family, providing a safe resource for the manufacture of antimicrobial feed additive for livestock. The active constituents from M. cordata are known to include benzylisoquinoline alkaloids (BIAs) such as sanguinarine (SAN) and chelerythrine (CHE), but their metabolic pathways have yet to be studied in this non-model plant. The active biosynthesis of SAN and CHE in M. cordata was first examined and confirmed by feeding ¹³C-labeled tyrosine. To gain further insights, we de novo sequenced the whole genome of M. cordata, the first to be sequenced from the Papaveraceae family. The M. cordata genome covering 378 Mb encodes 22,328 predicted protein-coding genes with 43.5% being transposable elements. As a member of basal eudicot, M. cordata genome lacks the paleohexaploidy event that occurred in almost all eudicots. From the genomics data, a complete set of 16 metabolic genes for SAN and CHE biosynthesis was retrieved, and 14 of their biochemical activities were validated. These genomics and metabolic data show the conserved BIA metabolic pathways in M. cordata and provide the knowledge foundation for future productions of SAN and CHE by crop improvement or microbial pathway reconstruction.