Metabolism of ganoderic acids by a Ganoderma lucidum cytochrome P450 and the 3-keto sterol reductase ERG27 from yeast

Identification of Key Post‐modification Enzymes Involved in the Biosynthesis of Lanostane‐type Triterpenoids in the Medicinal Mushroom Antrodia camphorata

Through different gene mining strategies, three key enzymes (AcCYP4, AcSDR6, AcSMT1) involved in the downstream biosynthesis of major lanostane-type triterpenoids were discovered and identified from Antrodia camphorata. The catalytic mechanisms of AcSDR6 were elucidated by crystal structure analysis. These post-modification enzymes could be used to synthesize at least 11 major Antrodia lanostanoids.

Integrated Transcriptomic and Targeted Metabolomic Analysis Reveals the Key Genes Involved in Triterpenoid Biosynthesis of Ganoderma lucidum

Ganoderma lucidum is a traditional Chinese medicinal fungus, and ganoderma triterpenoids (GTs) are one of the main bioactive compounds. These compounds have various pharmacological functions, including anti-tumor, antioxidant, anti-inflammatory, liver-protective, and immune-regulating effects. However, the manner in which they accumulate, and their biosynthesis mechanisms remain unclear. To screen for the genes that are involved in the biosynthetic pathway of GTs, this study analyzed the differential metabolites and differentially expressed genes (DEGs) among different growth stages of G. lucidum, including the primordia (P), the matured fruiting body (FM), and the post-spore fruiting bodies (FP) using targeted metabolomics and transcriptomics analysis, respectively. The results showed that a total of 699 components were detected, including lignans, terpenoids, amino acids and derivatives, and phenolic acids, among others. Among them, a total of 112 types of triterpenes were detected. Compared with the primordia, there were eight differential metabolites of triterpenoids, with three decreasing and five increasing in the FM stage. A comparison between the FM stage and the FP stage revealed that there were 13 differential metabolites of triterpenoids. A transcriptomics analysis showed that there were 371 DEGs in the P_vs_FM group, including 171 down-regulated genes and 200 up-regulated genes. In the FM_vs_FP group, 2567 DEGs were identified, with 1278 down-regulated genes and 1289 up-regulated genes. Through targeted metabolomics and transcriptome correlation analysis, six TFs and two CYP450s were significantly associated with four triterpenoid components. The results showed that these TFs and CYP450s were positively or negatively correlated with the four triterpenoid components. In addition, interestingly, some flavonoids and phenolic compounds, which have been reported in plants, were also detected in G. lucidum, indicating that it has the potential to be engineered into a strain capable of synthesizing flavonoid compounds. This study provides useful information about key genes involved in GT biosynthesis, but further exploration and in-depth research are needed to better understand the functions of these genes.

Mushroom-Mediated Redox Reactions

The application of biocatalysts in organic synthesis has grown significantly in recent years, and both academia and industry are continuously searching for novel biocatalysts capable of performing challenging chemical reactions. Mushrooms are a rich source of ligninolytic and secondary metabolite biosynthetic enzymes, and therefore were considered promising biocatalysts for organic synthesis. This review focuses on the broad utilization potential of mushroom-based biocatalysts and highlights key advances in mushroom-mediated redox reactions. It mainly includes the reduction of ketones and carboxylic acids, hydroxylation of aromatic and aliphatic compounds, epoxidation of olefins, oxidative cleavage of alkenes, and other uncommon reactions catalyzed by the whole cells or purified enzymes of mushroom origin. Overall, a comprehensive overview of the applications of mushrooms as biocatalysts in organic synthesis is provided, which puts this versatile microorganism in the spotlight of further research.

Whole-Genome Sequence Analysis of Flammulina filiformis and Functional Validation of Gad, a Key Gene for γ-Aminobutyric Acid Synthesis

Flammulina filiformis is one of the widely produced edible fungi worldwide. It is rich in γ-aminobutyric acid (GABA), a non-protein amino acid with important physiological functions in humans. To investigate the functions of key genes in the GABA metabolic pathway of F. filiformis, we isolated the monokaryon Fv-HL23-1 from the factory-cultivated F. filiformis strain Fv-HL23 and then sequenced and assembled the genome using the PacBio Sequel and Illumina NovaSeq sequencing platforms. The results showed that the genome comprised 140 scaffolds with a total length of 40.96 Mb, a GC content of 49.62%, an N50 of 917,125 bp, and 14,256 protein-coding genes. Phylogenetic analysis based on the whole genome revealed a close evolutionary relationship of Fv-HL23-1 with Armillaria mellea, Lentinula edodes, and Schizophyllum commune. A total of 589 carbohydrate-active enzymes were identified in the genome of Fv-HL23-1, suggesting its strong lignocellulose degradation ability, and 108 CYP450 gene family members were identified, suggesting important functions such as resistance to stress, secondary metabolite synthesis, and growth and development. The F. filiformis proteins glutamate decarboxylase 1 (Ff-GAD1) and glutamate decarboxylase 2 (Ff-GAD2), which may be responsible for GABA synthesis, were identified by protein alignment. Molecular docking analysis showed that Ff-GAD2 may have better catalytic activity than Ff-GAD1. To verify the function of Ff-gad2, its heterologous expression in the mycelia of the mononuclear Hypsizigus marmoreus was analyzed. Compared with wild type, the GABA content of mycelia was increased by 85.40-283.90%, the growth rate was increased by 9.39 ± 2.35%, and the fresh weight was increased by 18.44 ± 7.57%. Ff-GAD2 may play a catalytic role in GABA synthesis. In addition, the expression of the full-length Ff-gad2 gene was increased by 7.96 ± 1.39 times compared with the exon expression level in H. marmoreus mycelia, suggesting that the intron may contribute to the heterologous expression of Ff-GAD2. Based on whole-genome sequencing, we analyzed the enzyme system related to the important life activities of F. filiformis, focusing on the function of Ff-GAD, a key enzyme in the GABA synthesis pathway. The results lay a foundation for elucidating the GABA metabolism pathway of edible fungi and developing targeted breeding strategies for GABA-producing edible fungi.

Fungal degradation of phenylacetate focusing on CRISPR/Cas9-assisted characterization of two oxidative enzyme genes of Akanthomyces muscarius AM1091

The degradation of phenylacetate (PA) was investigated as a model to explore aromatic compound breakdown in the fungal system. Fungal strains capable of utilizing PA as their sole carbon source were isolated using a minimal solid medium supplemented with 0.5 % PA. Subsequent cultivation in minimum liquid medium revealed that selected fungal strains, including Trametes versicolor TV0876 and TV3295, Paecilomyces hepiali PH4477, and Akanthomyces muscarius AM1091, efficiently removed PA within 24 h. HPLC analysis of culture supernatants from various fungal strains revealed a time-dependent accumulation of 2-hydroxyphenylacetate (2-HPA) and 4-hydroxyphenylacetate (4-HPA), two key major metabolic products primarily found in ascomycetes and basidiomycetes, respectively. This suggests that the first hydroxylation of PA is catalyzed by two distinct hydroxylases, one for each fungal group. Furthermore, fungal species that make 4-HPA also produce phenylethanol (PE), indicating a distinct catabolic mechanism to remove PA by direct reduction of PA to PE. A. muscarius AM1091, identified as the most efficient PA degrader in this study, was studied further to determine the biochemical pathway of PA degradation. RNA-Seq and RT-PCR analyses of AM1091 revealed two oxidative enzyme genes, CYP1 and DIO4, upregulated in the presence of PA. Targeted disruption utilizing preassembled Cas9-gRNA ribonucleoprotein complexes and homologous DNAs harboring the URA3 gene as an auxotrophic marker resulted in the cyp1 and dio4 mutant strains. The cyp1 mutant was incapable of converting PA to 2-HPA, indicating its involvement in the C2 hydroxylation, whereas the dio4 mutant was unable to degrade 2,5-dihydroxyphenylacetate (2,5-DHPA), resulting in the accumulation of 2,5-DHPA. Our findings indicate that A. muscarius AM1091 degrades PA through the activities of CYP1 and DIO4 for the C2 hydroxylation and subsequent ring-opening reactions, respectively.

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.

Chemodiversity, pharmacological activity, and biosynthesis of specialized metabolites from medicinal model fungi Ganoderma lucidum

Ganoderma lucidum is a precious fungus, particularly valued for its dual use as both medicine and food. Ganoderic acids (GAs), the distinctive triterpenoids found in the Ganoderma genus, exhibit a wide range of pharmacological activities. However, the limited resources of GAs restrict their clinic usage and drug discovery. In this review, we presented a comprehensive summary focusing on the diverse structures and pharmacological activity of GAs in G. lucidum. Additionally, we discussed the latest advancements in the elucidation of GA biosynthesis, as well as the progress in heterosynthesis and liquid fermentation methods aimed at further increasing GA production. Furthermore, we summarized the omics data, genetic transformation system, and cultivation techniques of G. lucidum, described as medicinal model fungi. The understanding of Ganoderic acids chemodiversity and biosynthesis in medicinal model fungi Ganoderma lucidum will provide important insights into the exploration and utilization of natural products in medicinal fungi.

Combinatorial optimization and spatial remodeling of CYPs to control product profile

Activating inert substrates is a challenge in nature and synthetic chemistry, but essential for creating functionally active molecules. In this work, we used a combinatorial optimization approach to assemble cytochrome P450 monooxygenases (CYPs) and reductases (CPRs) to achieve a target product profile. By creating 110 CYP-CPR pairs and iteratively screening different pairing libraries, we demonstrated a framework for establishing a CYP network that catalyzes six oxidation reactions at three different positions of a chemical scaffold. Target product titer was improved by remodeling endoplasmic reticulum (ER) size and spatially controlling the CYPs' configuration on the ER. Out of 47 potential products that could be synthesized, 86% of the products synthesized by the optimized network was our target compound quillaic acid (QA), the aglycone backbone of many pharmaceutically important saponins, and fermentation achieved QA titer 2.23 g/L.

Development of a Transformation System for the Medicinal Fungus Sanghuangporus baumii and Acquisition of High-Value Strain

To further explore the molecular mechanism of triterpenoid biosynthesis and acquire high-value strain of Sanghuangporus baumii, the Agrobacterium tumefaciens-mediated transformation (ATMT) system was studied. The key triterpenoid biosynthesis-associated gene isopentenyl diphosphate isomerase (IDI) was transformed into S. baumii by ATMT system. Then, the qRT-PCR technique was used to analyze gene transcript level, and the widely targeted metabolomics was used to investigate individual triterpenoid content. Total triterpenoid content and anti-oxidant activity were determined by spectrophotometer. In this study, we for the first time established an efficient ATMT system and transferred the IDI gene into S. baumii. Relative to the wild-type (WT) strain, the IDI-transformant (IT) strain showed significantly higher transcript levels of IDI and total triterpenoid content. We then investigated individual triterpenoids in S. baumii, which led to the identification of 10 distinct triterpenoids. The contents of individual triterpenoids produced by the IT2 strain were 1.76-10.03 times higher than those produced by the WT strain. The triterpenoid production showed a significant positive correlation with the IDI gene expression. Besides, IT2 strain showed better anti-oxidant activity. The findings provide valuable information about the biosynthetic pathway of triterpenoids and provide a strategy for cultivating high-value S. baumii strains.

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.

Massive genome investigations reveal insights of prevalent introgression for environmental adaptation and triterpene biosynthesis in Ganoderma

Genome introgression is one of the driving forces that can increase species and genetic diversity and facilitate the adaptive evolution of organisms and biodiversity conservation. However, the genomic introgression and its contribution to biodiversity of macrofungi are still unclear. The genus Ganoderma is a typical macrofungal group that plays crucial roles in forest ecosystem as saprophytic organisms and plant pathogens, and is also involved in human health as medicinal mushrooms. Most public Ganoderma genomes are fragmented, and reference genomes and whole-genome information of diverse germplasm resources for many Ganoderma species are lacking, thus hindering functional and evolutionary genomic investigations among Ganoderma species. In this study, we provide high-quality genomes of 10 Ganoderma species and whole-genome variants data of 224 individuals from various ecoregions, enabling us to infer the phylogeny of Ganoderma species and their historical population dynamics. Based on whole-genome variants, widespread and genome-wide introgression among Ganoderma species is revealed. Genes with significant introgression signals were related to stress response, digestive absorption, and secondary metabolite synthesis, factors that may contribute to environmental adaptation and important biocomponent metabolism. CYP512U6, an essential functional gene in the CYP450 family related to Ganoderma triterpene synthesis, was detected with significant introgression and selection signals combined with Ganoderma metabolomic analysis, indicating that both ancient gene exchange and recent domestication have contributed to the categories and content of secondary metabolites of Ganoderma. The reference genomes, whole-genome variants, and metabolite profiles could serve as abundant and valuable genetic resources for evolution, ecology, and conservation investigations of Ganoderma species and other macrofungi.

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.

Evolution and enrichment of CYP5035 in Polyporales: functionality of an understudied P450 family

Abstract

Bioprospecting for innovative basidiomycete cytochrome P450 enzymes (P450s) is highly desirable due to the fungi’s enormous enzymatic repertoire and outstanding ability to degrade lignin and detoxify various xenobiotics. While fungal metagenomics is progressing rapidly, the biocatalytic potential of the majority of these annotated P450 sequences usually remains concealed, although functional profiling identified several P450 families with versatile substrate scopes towards various natural products. Functional knowledge about the CYP5035 family, for example, is largely insufficient. In this study, the families of the putative P450 sequences of the four white-rot fungi Polyporus arcularius, Polyporus brumalis, Polyporus squamosus and Lentinus tigrinus were assigned, and the CYPomes revealed an unusual enrichment of CYP5035, CYP5136 and CYP5150. By computational analysis of the phylogeny of the former two P450 families, the evolution of their enrichment could be traced back to the Ganoderma macrofungus, indicating their evolutionary benefit. In order to address the knowledge gap on CYP5035 functionality, a representative subgroup of this P450 family of P. arcularius was expressed and screened against a test set of substrates. Thereby, the multifunctional enzyme CYP5035S7 converting several plant natural product classes was discovered. Aligning CYP5035S7 to 102,000 putative P450 sequences of 36 fungal species from Joint Genome Institute-provided genomes located hundreds of further CYP5035 family members, which subfamilies were classified if possible. Exemplified by these specific enzyme analyses, this study gives valuable hints for future bioprospecting of such xenobiotic-detoxifying P450s and for the identification of their biocatalytic potential.

Graphical abstract

Key points

• The P450 families CYP5035 and CYP5136 are unusually enriched in P. arcularius.

• Functional screening shows CYP5035 assisting in the fungal detoxification mechanism.

• Some Polyporales encompass an unusually large repertoire of detoxification P450s.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00253-021-11444-2.

Integrative Analysis of Selected Metabolites and the Fungal Transcriptome during the Developmental Cycle of Ganoderma lucidum Strain G0119 Correlates Lignocellulose Degradation with Carbohydrate and Triterpenoid Metabolism

To systemically understand the biosynthetic pathways of bioactive substances, including triterpenoids and polysaccharides, in Ganoderma lucidum, the correlation between substrate degradation and carbohydrate and triterpenoid metabolism during growth was analyzed by combining changes in metabolite content and changes in related enzyme expression in G. lucidum over 5 growth phases. Changes in low-polarity triterpenoid content were correlated with changes in glucose and mannitol contents in fruiting bodies. Additionally, changes in medium-polarity triterpenoid content were correlated with changes in the lignocellulose content of the substrate and with the glucose, trehalose, and mannitol contents of fruiting bodies. Weighted gene coexpression network analysis (WGCNA) indicated that changes in trehalose and polyol contents were related to carbohydrate catabolism and polysaccharide synthesis. Changes in triterpenoid content were related to expression of the carbohydrate catabolic enzymes laccase, cellulase, hemicellulase, and polysaccharide synthase and to the expression of several cytochrome P450 monooxygenases (CYPs). It was concluded that the products of cellulose and hemicellulose degradation participate in polyol, trehalose, and polysaccharide synthesis during initial fruiting body formation. These carbohydrates accumulate in the early phase of fruiting body formation and are utilized when the fruiting bodies mature and a large number of spores are ejected. An increase in carbohydrate metabolism provides additional precursors for the synthesis of triterpenoids. IMPORTANCE Most studies of G. lucidum have focused on its medicinal function and on the mechanism of its activity, whereas the physiological metabolism and synthesis of bioactive substances during the growth of this species have been less studied. Therefore, theoretical guidance for cultivation methods to increase the production of bioactive compounds remains lacking. This study integrated changes in the lignocellulose, carbohydrate, and triterpenoid contents of G. lucidum with enzyme expression from transcriptomics data using WGCNA. The findings helped us better understand the connections between substrate utilization and the synthesis of polysaccharides and triterpenoids during the cultivation cycle of G. lucidum. The results of WGCNA suggest that the synthesis of triterpenoids can be enhanced not only through regulating the expression of enzymes in the triterpenoid pathway, but also through regulating carbohydrate metabolism and substrate degradation. This study provides a potential approach and identifies enzymes that can be targeted to regulate lignocellulose degradation and accelerate the accumulation of bioactive substances by regulating substrate degradation in G. lucidum.

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.

Cytochrome P450 enzymes in fungal natural product biosynthesis

Covering: 2015 to the end of 2020 Fungal-derived polyketides, non-ribosomal peptides, terpenoids and their hybrids contribute significantly to the chemical space of total natural products. Cytochrome P450 enzymes play essential roles in fungal natural product biosynthesis with their broad substrate scope, great catalytic versatility and high frequency of involvement. Due to the membrane-bound nature, the functional and mechanistic understandings for fungal P450s have been limited for quite a long time. However, recent technical advances, such as the efficient and precise genome editing techniques and the development of several filamentous fungal strains as heterologous P450 expression hosts, have led to remarkable achievements in fungal P450 studies. Here, we provide a comprehensive review to cover the most recent progresses from 2015 to 2020 on catalytic functions and mechanisms, research methodologies and remaining challenges in the fast-growing field of fungal natural product biosynthetic P450s.

Transcriptome dynamics and metabolite analysis revealed the candidate genes and regulatory mechanism of ganoderic acid biosynthesis during liquid superficial-static culture of Ganoderma lucidum

Ganoderic acid (GA), an important secondary metabolite of Ganoderma lucidum, exhibited many significant pharmacological activities. In this study, the biosynthetic mechanism of GAs was investigated by comparing metabolites and transcriptome dynamics during liquid superficial‐static culture (LSSC) and submerged culture (SC). LSSC was a better method to produce GA because thirteen GAs were identified from mycelia by UPLC‐QTOF‐MS, and the content of all GAs was higher in LSSC than in SC. Ergosterol was accumulated during the SC process in G. lucidum. Transcriptome dynamics analysis revealed CYP5150L8 was the key gene regulating lanosterol flux into GA biosynthesis. Other sixteen CYP450 genes were significantly higher expressed during the culture time in LSSC and could be potential candidate genes associated with the biosynthesis of different GAs. In addition, six of the ten expressed genes in ergosterol biosynthetic pathway shown upregulated at some time points in SC. These results not only provide a fundamental information of the key genes in ergosterol and GA biosynthetic pathway, but also provide directions for future elucidating the regulatory mechanisms of GAs in G. lucidum and enabling us to promote the development and utilization of LSSC at the industrial level.

Function of ceramide synthases on growth, ganoderic acid biosynthesis and sphingolipid homeostasis in Ganoderma lucidum

Ceramide synthases (CERSs) catalyse an N-acyltransferase reaction using long-chain base (LCB) and fatty acyl-coenzyme A (CoA) as substrates to synthesize ceramide (Cer), which is the backbone of all complex sphingolipids. In the present study, three CERSs (LAG1, LAG2 and LAG3) form Ganoderma lucidum were analysed. The silencing of lag1 by RNA interference reduced ganoderic acid biosynthesis and Cer and complex sphingolipids contents, which contain long-chain-fatty-acids (LCFAs, including C16 and C18). In contrast, the silencing of lag2 or lag3 did not result in obvious phenotypic and sphingolipid homeostasis changes, although the lag2/lag3 double-silenced mutants exhibited increased ganoderic acid biosynthesis as well as reduced growth, reduced Cer and complex sphingolipids contents, which contain very-long-chain fatty acids (VLCFAs, including C22, C24 and C26). The results of the present study indicate that the three assayed CERSs have distinct physiological functions and substrate specificities in G. lucidum.

Enhanced production of individual ganoderic acids by integrating Vitreoscilla haemoglobin expression and calcium ion induction in liquid static cultures of Ganoderma lingzhi

Ganoderic acids produced by Ganoderma exhibit anticancer and antimetastatic activities. A novel approach by combining Vitreoscilla haemoglobin (VHb) expression and calcium ion induction was developed to enhance ganoderic acid (GA) production in liquid static cultures of G. lingzhi. The maximum contents of GA-O, GA-S and GA-Me were 1451.33 ± 67.50, 1431.23 ± 79.74 and 1283.81 ± 85.13 μg per 100 mg cell weight, respectively under the integrated approach, which are the highest contents as ever reported in Ganoderma. The contents of squalene and lanosterol were increased by 2.0- and 3.0-fold in this case compared with those in the control. The transcription levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase, farnesyl-diphosphate synthase, squalene synthase and cytochrome P450 CYP5150L8 were upregulated by 2.56-, 3.31-, 2.59- and 6.12-fold respectively. Additionally, the expression of VHb improved the ratio of type I to type II GA in liquid static cultivation of G. lingzhi. The transcription levels of cyp512a2, cyp512v2 and cyp512a13, candidate cytochrome P450 genes involved in oxidative modification of the lanostane skeleton in GA biosynthesis, were also increased by 2.28-, 2.65- and 3.54-fold in the VHb-expressing strain respectively. Our results illustrated that the approach described here efficiently improved GA production in G. lingzhi fermentation.

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.