Comparative genomic and transcriptomic analyses of the Fuzhuan brick tea-fermentation fungus Aspergillus cristatus

Morphological variation and expressed sequence tags-simple sequence repeats-based genetic diversity of Aspergillus cristatus in Chinese dark tea

Introduction

Aspergillus cristatus is a homothallic fungus that is used in the natural fermentation process of Chinese Fuzhuan tea and has been linked to the production of bioactive components. However, not much is known about the variations present in the fungus. To understand the variation of the dominant microorganism, A. cristatus, within dark tea, the present study investigated the genetic and morphological diversity of 70 A. cristatus collected across six provinces of China.

Methods

Expressed sequence tags-simple sequence repeats (EST-SSR) loci for A. cristatus were identified and corresponding primers were developed. Subsequently, 15 specimens were selected for PCR amplification.

Results

The phylogenetic tree obtained revealed four distinct clusters with a genetic similarity coefficient of 0.983, corresponding to previously identified morphological groups. Five strains (A1, A11, B1, D1, and JH1805) with considerable differences in EST-SSR results were selected for further physiological variation investigation. Microstructural examinations revealed no apparent differentiation among the representative strains. However, colony morphology under a range of culture media varied substantially between strains, as did the extracellular enzymatic activity (cellulase, pectinase, protease, and polyphenol oxidase); the data indicate that there are differences in physiological metabolic capacity among A. cristatus strains.

Discussion

Notably, JH1805, B1, and A11 exhibited higher enzymatic activity, indicating their potential application in the production of genetically improved strains. The findings provide valuable insights into species identification, genetic diversity determination, and marker-assisted breeding strategies for A. cristatus.

Material Composition Characteristics of Aspergillus cristatus under High Salt Stress through LC-MS Metabolomics

Aspergillus cristatus is a crucial edible fungus used in tea fermentation. In the industrial fermentation process, the fungus experiences a low to high osmotic pressure environment. To explore the law of material metabolism changes during osmotic pressure changes, NaCl was used here to construct different osmotic pressure environments. Liquid chromatography-mass spectrometry (LC-MS) combined with multivariate analysis was performed to analyze the distribution and composition of A. cristatus under different salt concentrations. At the same time, the in vitro antioxidant activity was evaluated. The LC-MS metabolomics analysis revealed significant differences between three A. cristatus mycelium samples grown on media with and without NaCl concentrations of 8% and 18%. The contents of gibberellin A3, A124, and prostaglandin A2 related to mycelial growth and those of arabitol and fructose-1,6-diphosphate related to osmotic pressure regulation were significantly reduced at high NaCl concentrations. The biosynthesis of energy-related pantothenol and pantothenic acid and antagonism-related fluvastatin, aflatoxin, and alternariol significantly increased at high NaCl concentrations. Several antioxidant capacities of A. cristatus mycelia were directly related to osmotic pressure and exhibited a significant downward trend with an increase in environmental osmotic pressure. The aforementioned results indicate that A. cristatus adapts to changes in salt concentration by adjusting their metabolite synthesis. At the same time, a unique set of strategies was developed to cope with high salt stress, including growth restriction, osmotic pressure balance, oxidative stress response, antioxidant defense, and survival competition.

Reexamination of Aspergillus cristatus phylogeny in dark tea: Characteristics of the mitochondrial genome

To enhance our understanding of Aspergillus cristatus, an important functional microorganism, the characteristics of its mitochondrial genome were analyzed and compared with related species. The mitochondrial genome of A. cristatus was determined to be 77,649 bp in length, with 15 protein-coding regions. Notably, its length surpassed that of the other species, primarily attributable to the intron length. Gene order exhibited significant variations, with greater conservation observed in the genus Penicillium compared to Aspergillus. Phylogenetic tree analyses indicated that the genera Aspergillus and Penicillium are closely related but monophyletic. Furthermore, the phylogenetic tree constructed based on protein-coding genes effectively distinguished all strains with high branching confidence. This approach provides a robust reflection of the evolutionary relationship between A. cristatus and its related species, offering potential for the development of molecular markers suitable for Aspergillus and Penicillium.

Role of Pmk1, Mpk1, or Hog1 in the mitogen-activated protein kinase pathway of Aspergillus cristatus

Aspergillus cristatus is a probiotic fungus known for its safety and abundant secondary metabolites, making it a promising candidate for various applications. However, limited progress has been made in researching A. cristatus due to challenges in genetic manipulation. The mitogen-activated protein kinase (MAPK) signaling pathway is involved in numerous physiological processes, but its specific role in A. cristatus remains unclear. In this study, we successfully developed an efficient polyethylene glycol (PEG)-mediated protoplast transformation method for A. cristatus, enabling us to investigate the function of Pmk1, Mpk1, and Hog1 in the MAPK signaling pathway. Our findings revealed that Pmk1, Mpk1, and Hog1 are crucial for sexual reproduction, melanin synthesis, and response to external stress in A. cristatus. Notably, the deletion of Pmk1, Mpk1, or Hog1 resulted in the loss of sexual reproduction capability in A. cristatus. Overall, this research on MAPK will contribute to the continued understanding of the reproductive strategy and melanin synthesis mechanism of A. cristatus.

Characteristic volatiles of Fu brick tea formed primarily by extracellular enzymes during Aspergillus cristatus fermentation

Fu brick tea (FBT) has unique "fungal flower" aroma traits, but its source of crucial aroma compounds is still controversial. Aspergillus cristatus is the dominant fungus that participated in the fermentation of FBT. In this study, volatiles of Aspergillus cristatus and corresponding fermented FBT were examined using GC × GC-Q-TOFMS. A total of 59 volatiles were shared by three strains of Aspergillus cristatus isolated from representative FBT. Among them, 1-octen-3-ol and 3-octanone were the most abundant. A total of 133 volatiles were screened as typical FBT volatiles from three FBTs fermented by the corresponding fungi. Aspergillus cristatus and FBT had only 29 coexisting volatiles, indicating that the volatiles of Aspergillus cristatus could not directly contribute to the aroma of FBT. The results of no significant correlation between volatile content in FBT and volatile content in Aspergillus cristatus suggested that intracellular metabolism of Aspergillus cristatus was not a direct driver of FBT aroma formation. Metabolic pathway analysis and proteomic analysis showed that the aroma in FBT was mainly formed by the enzymatic reaction of extracellular enzymes from Aspergillus cristatus. This study enriched our understanding of Aspergillus cristatus in the aroma formation process of FBT.

Metabolomic and transcriptomic analyses reveal comparisons against liquid-state fermentation of primary dark tea, green tea and white tea by Aspergillus cristatus

Liquid-state fermentation (LSF) of tea leaves is a promising way to obtain tea-based nutraceutical products rich in various bioactive compounds. In the study, the changes of bioactive compounds, tea pigments and complex metabolites from LSF of primary dark tea, green tea and white tea infusions with Aspergillus cristatus were determined. Chemical analyses revealed that soluble sugars, monosaccharide composition, total polyphenols, total flavonoids, free amino acids, soluble proteins and tea pigments were changed in different ways. An untargeted metabolomic analysis and ribonucleic acid sequencing (RNA-seq) based transcriptomic analysis were performed to investigate the metabolic differentiation and clarify the key differentially expressed genes (DEGs, fold change >2 and p < 0.05), showing that amino acid metabolism, carbohydrate metabolism and lipid metabolism were the most enriched pathways during A. cristatus fermentation of primary dark tea, green tea and white tea infusions. In addition, glycerophospholipid metabolism, linoleic acid metabolism and phenylalanine metabolism were greatly accumulated in the fermentation of primary dark tea and white tea infusions; Pyruvate metabolism, glycolysis/gluconeogenesis, fatty acid degradation, tyrosine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis and valine and leucine, isoleucine degradation were greatly accumulated in the fermentation of primary dark tea and green tea infusions; Starch and sucrose metabolism was greatly accumulated in the fermentation of green tea and white tea infusions; Galactose metabolism was significantly enhanced in the fermentation of primary dark tea infusion; Amino sugar and nucleotide sugar metabolism, sphingolipid metabolism and alanine, aspartate and glutamate metabolism were significantly enhanced in the fermentation of green tea infusion. Besides, some other pathways involving aminobenzoate degradation, biosynthesis of cofactors, pyrimidine metabolism, benzoxazinoid biosynthesis and phenazine biosynthesis, tropane, piperidine and pyridine alkaloid biosynthesis and flavone and flavonol biosynthesis also differed from each other. These findings support that A. cristatus plays a vital role in the biochemical and genetic regulation of metabolite profile, and could be considered a potential prospect for better use of A. cristatus on different kinds of tea materials.

Changes in the volatile compounds and characteristic aroma during liquid-state fermentation of instant dark tea by Eurotium cristatum

Instant dark tea (IDT) was prepared by liquid-state fermentation inoculating Eurotium cristatum. The changes in the volatile compounds and characteristic aroma of IDT during fermentation were analyzed using gas chromatography-mass spectrometry by collecting fermented samples after 0, 1, 3, 5, 7, and 9 days of fermentation. Components with high odor activity (log₂^FD ≥ 5) were verified by gas chromatography-olfactometry. A total of 107 compounds showed dynamic changes during fermentation over 9 days, including 17 alcohols, 7 acids, 10 ketones, 11 esters, 8 aldehydes, 37 hydrocarbons, 4 phenols, and 13 other compounds. The variety of flavor compounds increased gradually with time within the early stage and achieved a maximum of 79 compounds on day 7 of fermentation. β-Damascenone showed the highest odor activity (log₂^FD = 9) in the day 7 sample, followed by linalool and geraniol. These results indicate that fungal fermentation is critical to the formation of these aromas of IDT.

Eurotium cristatum reduces obesity by alleviating gut microbiota dysbiosis and modulating lipid and energy metabolism

BACKGROUND

Fuzhuan brick tea (FBT) has been shown to prevent obesity, but little is known about the effect of Eurotium cristatum, a critical fungus from FBT. This study examined the effects of live E. cristatum on lipid metabolism and gut microbiota composition in high-fat (HF) diet-induced obese mice.

RESULTS

Male HF diet-fed mice were treated with E. cristatum for 12 weeks. The results showed that E. cristatum administration caused strong inhibition against HF-induced body weight gain, dyslipidemia and liver oxidative stress damage. Additionally, Firmicutes and Bacteroidetes in phylum level and six types of bacterial including short-chain fatty acids (SCFAs) producing bacteria in genus level were found to be significantly changed in E. cristatum treated mice as compared to HF fed mice. As expected, E. cristatum could increase total SCFAs levels in feces. Interestingly, E. cristatum markedly increased the proportion of Akkermansia to resist obesity. Functional prediction analysis indicated that E. cristatum changed lipid and energy metabolism. Furthermore, E. cristatum ingestion can modulate hepatic acetyl-coa carboxylase (ACC), fatty acid synthase (FAS), sterol-regulatory element binding protein-1 (SREBP-1) and adipose uncoupling protein-1 (UCP-1) expression.

CONCLUSION

Conclusively, these findings suggest that E. cristatum can prevent the HF-induced lipid accumulation and other complications by modulating gut microbiota, lipid and energy metabolism. © 2022 Society of Chemical Industry.

Achog1 is required for the asexual sporulation, stress responses and pigmentation of Aspergillus cristatus

Aspergillus cristatus is the dominant fungus during the fermentation of Fuzhuan brick tea; hypotonic conditions only induce its sexual development to produce ascospores, while hypertonic conditions only induce its asexual development to produce conidia, indicating that osmotic stress can regulate spore production in A. cristatus. However, the underlying regulatory mechanism is unclear. In this study, the role of Achog1, which is homologous to hog1 from Saccharomyces cerevisiae, in sporulation, different kinds of stress responses and pigment production was investigated. Deletion mutants of Achog1 were obtained by homologous recombination. Phenotypic observations showed that the time required to produce conidia was delayed, and the number of conidia produced was significantly reduced in the deletion mutants of Achog1 in hypertonic media, indicating that Achog1 plays a positive role in asexual development. Stress sensitivity tests showed that ΔAchog1 strains were sensitive to hyperosmolarity, and the order of the sensitivity of ΔAchog1 to different osmotic regulators was 3 M sucrose >3 M NaCl >3 M sorbitol. Moreover, the deletion mutants were sensitive to high oxidative stress. pH sensitivity tests indicated that Achog1 inhibited the growth of A. cristatus under alkaline stress. Additionally, pigmentation was decreased in the Achog1 deletion mutants compared with the WT. All the above developmental defects were reversed by the reintroduction of the Achog1 gene in ΔAchog1. Pull-down and LC-MS/MS analysis showed that the expression levels of proteins interacting with Achog1 were significantly different under low and high osmotic stress, and proteins related to conidial development were present only in the cultures treated with hyperosmotic stress. Transcription profiling data showed that Achog1 suppressed the expression of several genes related to asexual development, osmotic and oxidative stress resistance. On the basis of gene knockout, pull-down mass spectrometry and RNA-seq analyses, a regulatory pathway for Achog1 was roughly identified in A. cristatus.

The role of Acpbs2 in the asexual sporulation, stress response and carbon metabolism of Aspergillus cristatus

Aspergillus cristatus is the dominant fungus during the fermentation of Fuzhuan brick tea, hypotonic conditions only induced its sexual development to produce ascospores, while hypertonic conditions only induced its asexual development to produce conidia, indicating that osmotic stress can regulate spore production in A. cristatus. However, the underlying regulatory mechanism is unclear. In this study, the roles of Acpbs2, which is homologous to pbs2 from Saccharomyces cerevisiae, in sporulation, stress responses, the color of colonies, and carbon metabolism were explored in A. cristatus. Deletion mutants of Acpbs2 were obtained by homologous recombination. The time required to produce conidia was delayed, and the number of conidia produced was significantly reduced in hypertonic media in ΔAcpbs2 by phenotypic observations, indicating that Acpbs2 plays a positive role in asexual development. Stress sensitivity tests showed that the order of the sensitivity of ΔAcpbs2 to different osmotic regulators was 3 M NaCl > 3 M sucrose > 3 M sorbitol. Moreover, the deletion mutants were sensitive to high oxidative stress. The growth of the Acpbs2 deletion mutant was inhibited under alkaline-pH stress, indicating that Acpbs2 is involved in high pH stress tolerance. Additionally, compared with the wild type, the colony color of the Acpbs2 deletion mutant became lighter. All the above developmental defects were reversed by the reintroduction of the Acpbs2 gene in ΔAcpbs2. Transcriptome data showed that Acpbs2 regulated the expression of several genes related to conidial development, osmotic stress, oxidative stress, and carbon metabolism. More importantly, the interaction between Acpbs2 and its downstream gene Achog1 was verified by yeast two-hybrid assays. We speculated that this interaction might regulate the osmotic stress response, the oxidative stress response, and asexual sporulation in A. cristatus, which will be one of the focuses of our future research.

Anti-aging efficacy of solid-state fermented ginseng with Aspergillus cristatus and its active metabolites

Aspergillus cristatus is a beneficial fungus of microbial fermented teas such as China’s Fuzhuan brick tea and Pu-erh tea, and is commonly called golden flower fungus (GFF) because its cleistothecium has a yellow millet or sand grain shape. Since natural materials fermented with GFF exhibit various physiological activities, a new active cosmeceutical ingredient was developed by solid-state fermentation of ginseng, a famous active material for healthy skin, with GFF. The extract of solid-state fermented ginseng with GFF (GFFG) exhibited potent anti-aging efficacy on the skin such as the increase of hyaluronic acid synthesis, aquaporin expression, and mRNA level of filaggrin in HaCaT keratinocyte. GFFG also inhibited the expression of MMP-1 increased by TNF-α in human dermal fibroblast. Sophisticated chromatographic and spectroscopic studies have elucidated isodihydroauroglaucin and flavoglaucin as the metabolites which were not present in ginseng extract nor GFF extract alone. Bioassay of these metabolites revealed that these compounds were part of active principles of GFFG. These results suggest that GFFG would be a potential active ingredient in anti-aging cosmeceutical products.

Overexpression of llm1 Affects the Synthesis of Secondary Metabolites of Aspergillus cristatus

Putative methyltransferases are thought to be involved in the regulation of secondary metabolites in filamentous fungi. Here, we report the effects of overexpression of a predicted LaeA-like methyltransferase gene llm1 on the synthesis of secondary metabolites in Aspergillus cristatus. Our results revealed that overexpression of the gene llm1 in A. cristatus significantly hindered the production of conidia and enhanced sexual development, and reduced oxidative tolerance to hydrogen peroxide. Compared with the wild-type, the metabolic profile of the overexpression transformant was distinct, and the contents of multiple secondary metabolites were markedly increased, mainly including terpenoids and flavonoids, such as (S)-olEuropeic acid, gibberellin A62, gibberellin A95, ovalitenone, PD 98059, and 1-isomangostin. A total of 600 significantly differentially expressed genes (DEGs) were identified utilizing transcriptome sequencing, and the DEGs were predominantly enriched in transmembrane transport and secondary metabolism-related biological processes. In summary, the strategy of overexpressing global secondary metabolite regulators successfully activated the expression of secondary metabolite gene clusters, and the numerous secondary metabolites were greatly strengthened in A. cristatus. This study provides new insights into the in-depth exploitation and utilization of novel secondary metabolites of A. cristatus.

Multiplex PCR Identification of Aspergillus cristatus and Aspergillus chevalieri in Liupao Tea Based on Orphan Genes

“Golden flower” fungi in dark tea are beneficial to human health. The rapid identification method of “golden flower” fungi can verify the quality of dark tea products and ensure food safety. In this study, 6 strains were isolated from Liupao tea. They were respectively identified as A. cristatus, A. chevalieri, and A. pseudoglaucus. A. pseudoglaucus was reported as Liupao tea “golden flower” fungus for the first time. It was found that the ITS and BenA sequences of A. cristatus and A. chevalieri were highly conserved. It is difficult to clearly distinguish these closely related species by ITS sequencing. To rapidly identify species, multiplex PCR species-specific primers were designed based on orphan genes screened by comparative genomics analysis. Multiplex PCR results showed that orphan genes were specific and effective for the identification of A. cristatus and A. chevalieri isolated from Liupao tea and Fu brick tea. We confirmed that orphan genes can be used for identification of closely related Aspergillus species. Validation showed that the method is convenient, rapid, robust, sequencing-free, and economical. This promising method will be greatly beneficial to the dark tea processing industry and consumers.

Genome Mining and Analysis of PKS Genes in Eurotium cristatum E1 Isolated from Fuzhuan Brick Tea

Eurotium cristatum as the dominant fungi species of Fuzhuan brick tea in China, can produce multitudinous secondary metabolites (SMs) with various bioactivities. Polyketides are a very important class of SMs found in E. cristatum and have gained extensive attention in recent years due to their remarkable diversity of structures and multiple functions. Therefore, it is necessary to explore the polyketides produced by E. cristatum at the genomic level to enhance its application value. In this paper, 12 polyketide synthase (PKS) genes were found in the whole genome of E. cristatum E1 isolated from Fuzhuan brick tea. In addition, the qRT-PCR results further demonstrated that these genes were expressed. Moreover, metabolic analysis demonstrated E. cristatum E1 can produce a variety of polyketides, including citreorosein, emodin, physcion, isoaspergin, dihydroauroglaucin, iso-dihydroauroglaucin, aspergin, flavoglaucin and auroglaucin. Furthermore, based on genomic analysis, the putative secondary metabolites clusters for emodin and flavoglaucin were proposed. The results reported here will lay a good basis for systematically mining SMs resources of E. cristatum and broadening its application fields.

Solid-State Fermentation With Aspergillus cristatus Enhances the Protopanaxadiol- and Protopanaxatriol-Associated Skin Anti-aging Activity of Panax notoginseng

A metabolomics approach was used to profile metabolites of Panax notoginseng fermented with Aspergillus cristatus in two ways, liquid-state fermentation (LF-P) and solid-state fermentation (SSF-P) and examine metabolite markers representing antioxidant activity and skin anti-aging. Protopanaxadiol (PPD) and protopanaxatriol (PPT) contents were higher in SSF-P than in LF-P and showed a multiplicative increase over the fermentation period of four days. PPD and PPT levels also correlated with antioxidant and anti-aging effects in skin, based on the mRNA expression of dermal extracellular matrix components. In the bioactivity validation assays, PPD and PPT significantly improved the expression of type-I collagen, fibrillin-1, and elastin in human dermal fibroblasts from both young and old subjects; these were comparable with the effects of the SSF-P extracts. Overall, our results suggest that changes in the metabolites of P. notoginseng fermented with A. cristatus enhance the quality and availability of bioactive compounds associated with skin anti-aging.

A critical review of Fuzhuan brick tea: processing, chemical constituents, health benefits and potential risk

Fuzhuan brick tea (FBT) is a traditional popular beverage in the border regions of China. Nowadays, FBT has been attracted great attention due to its uniquely flavor and various health-promoting functions. An increasing number of efforts have been devoted to the studies on health benefits and chemistry of FBT over the last decades. However, FBT was still received much less attention than green tea, oolong tea and black tea. Therefore, it is necessary to review the current encouraging findings about processing, microorganisms, chemical constituents, health benefits and potential risk of FBT. The fungus fermentation is the key stage for processing of FBT, which is involved in a complex and unique microbial fermentation process. The fungal community in FBT is mainly dominated by "golden flower" fungi, which is identified as Aspergillus cristatus. A great diversity of novel compounds is formed and identified after a series of biochemical reactions during the fermentation process of FBT. FBT shows various biological activities, such as antioxidant, anti-inflammatory, anti-obesity, anti-bacterial, and anti-tumor activities. Furthermore, the potential risk of FBT was also discussed. It is expected that this review could be useful for stimulating further research of FBT.

Role of AcndtA in cleistothecium formation, osmotic stress response, pigmentation and carbon metabolism of Aspergillus cristatus

As the dominant fungus during the fermentation of Fuzhuan brick tea, Aspergillus cristatus is easily induced to undergo a sexual cycle under low-salt stress. However, the underlying regulatory mechanism of sexual reproduction is unclear. Here, we report a P53-like transcription factor AcndtA, which encodes an NDT80 DNA binding protein and regulates fungal reproduction, pigmentation and the stress response. Both insertion and deletion mutants of AcndtA exhibited a complete blockade of cleistothecium formation, and overexpressing AcndtA strains (OE: AcndtA) exhibited significantly reduced cleistothecium production, indicating that AcndtA plays a vital role in sexual development. Osmotic stress tests showed that overexpression of AcndtA had a negative impact on growth and conidia production. Additionally, AcndtA insertion, deletion and overexpression mutants exhibited reduced pigment formation. All the above developmental defects were reversed by the re-introduction of the AcndtA gene in ΔAcndtA. Moreover, the growth of AcndtA mutants in carbon-limited medium was better than that of the WT and OE: AcndtA strains, indicating that AcndtA is involved in carbon metabolism. Transcriptional profiling data showed that AcndtA regulated the expression of several genes related to development, osmotic stress and carbon metabolism.

Analysis of the Fungal Diversity and Community Structure in Sichuan Dark Tea During Pile-Fermentation

The fungi present during pile-fermentation of Sichuan dark tea play a pivotal role in the development of its aroma and physical characteristics. Samples of tea leaves were collected on days 0 (YC-raw material), 8 (W1-first turn), 16 (W2-second turn), 24 (W3-third turn), and 32 (W4-out of pile) during pile-fermentation. High-throughput sequencing revealed seven phyla, 22 classes, 41 orders, 85 families, 128 genera, and 184 species of fungi. During fermentation, the fungal diversity index declined from the W1 to W3 stages and then increased exponentially at the W4 stage. A bar plot and heatmap revealed that Aspergillus, Thermomyces, Candida, Debaryomyces, Rasamsonia, Rhizomucor, and Thermoascus were abundant during piling, of which Aspergillus was the most abundant. Cluster analysis revealed that the W4 stage of fermentation is critical for fungal growth, diversity, and the community structure in Sichuan dark tea. This study revealed the role of fungi during pile-fermentation in the development of the essence and physical characteristics of Sichuan dark tea. This study comes under one of the Sustainable Development Goals of United Nations Organization (UNO) to "Establish Good Health and Well-Being."

Distribution of methionine sulfoxide reductases in fungi and conservation of the free-methionine-R-sulfoxide reductase in multicellular eukaryotes

Methionine, either as a free amino acid or included in proteins, can be oxidized into methionine sulfoxide (MetO), which exists as R and S diastereomers. Almost all characterized organisms possess thiol-oxidoreductases named methionine sulfoxide reductase (Msr) enzymes to reduce MetO back to Met. MsrA and MsrB reduce the S and R diastereomers of MetO, respectively, with strict stereospecificity and are found in almost all organisms. Another type of thiol-oxidoreductase, the free-methionine-R-sulfoxide reductase (fRMsr), identified so far in prokaryotes and a few unicellular eukaryotes, reduces the R MetO diastereomer of the free amino acid. Moreover, some bacteria possess molybdenum-containing enzymes that reduce MetO, either in the free or protein-bound forms. All these Msrs play important roles in the protection of organisms against oxidative stress. Fungi are heterotrophic eukaryotes that colonize all niches on Earth and play fundamental functions, in organic matter recycling, as symbionts, or as pathogens of numerous organisms. However, our knowledge on fungal Msrs is still limited. Here, we performed a survey of msr genes in almost 700 genomes across the fungal kingdom. We show that most fungi possess one gene coding for each type of methionine sulfoxide reductase: MsrA, MsrB, and fRMsr. However, several fungi living in anaerobic environments or as obligate intracellular parasites were devoid of msr genes. Sequence inspection and phylogenetic analyses allowed us to identify non-canonical sequences with potentially novel enzymatic properties. Finaly, we identified several ocurences of msr horizontal gene transfer from bacteria to fungi.

Influence of Eurotium cristatum and Aspergillus niger individual and collaborative inoculation on volatile profile in liquid-state fermentation of instant dark teas

The three instant dark teas were produced from instant green tea (IGT) by liquid-state fermentations using the microorganisms Eurotium cristatum (EFT), Aspergillus niger (AFT), and sequential inoculation of E. cristatum/A. niger (EAFT), respectively. The volatile compounds of four tea samples were extracted by headspace-solid phase microextraction (HS-SPME) and analyzed using gas chromatography-mass spectrometry (GC-MS) coupled with chemometrics. A total of 97 volatile compounds were tentatively identified to distinguish three fermented instant dark from IGT. Alcohols, acids, esters, ketones, aldehydes, and heterocyclics could be clearly distinguished by principal component analysis (PCA), venn diagram, heatmap analysis and hierarchical cluster analysis (HCA). Descriptive sensory analysis revealed that AFT had a moldy, woody and herbal aroma; EFT showed woody and herbal aroma; and EAFT smelled an herbal, sweet, minty and floral aroma. This study indicates that fermentation using different microorganisms is critical in forming unique aroma characteristics of instant dark teas.

Microbial communities and gene contributions in smokeless tobacco products

Smokeless tobacco products (STP) contain bacteria, mold, and fungi due to exposure from surrounding environments and tobacco processing. This has been a cause for concern since the presence of microorganisms has been linked to the formation of highly carcinogenic tobacco-specific nitrosamines. These communities have also been reported to produce toxins and other pro-inflammatory molecules that can cause mouth lesions and elicit inflammatory responses in STP users. Moreover, microbial species in these products could transfer to the mouth and gastrointestinal tract, potentially altering the established respective microbiotas of the consumer. Here, we present the first metagenomic analysis of select smokeless tobacco products, specifically US domestic moist and dry snuff. Bacterial, eukaryotic, and viral species were found in all tobacco products where 68% of the total species was comprised of Bacteria with 3 dominant phyla but also included 32% Eukarya and 1% share abundance for Archaea and Viruses. Furthermore, 693,318 genes were found to be present and included nitrate and nitrite reduction and transport enzymes, antibiotic resistance genes associated with resistance to vancomycin, β-lactamases, their derivatives, and other antibiotics, as well as genes encoding multi-drug transporters and efflux pumps. Additional analyses showed the presence of endo- and exotoxin genes in addition to other molecules associated with inflammatory responses. Our results present a novel aspect of the smokeless tobacco microbiome and provide a better understanding of these products' microbiology. KEY POINTS: • The findings presented will help understand microbial contributions to overall STP chemistries. • Gene function categorization reveals harmful constituents outside canonical forms. • Pathway genes for TSNA precursor activity may occur at early stages of production. • Bacteria in STPs carry antibiotic resistance genes and gene transfer mechanisms.

Modulation of gut homeostasis by exopolysaccharides from Aspergillus cristatus (MK346334), a strain of fungus isolated from Fuzhuan brick tea, contributes to immunomodulatory activity in cyclophosphamide-treated mice

In this study, the crude exopolysaccharides (CEPSs) from fungus Aspergillus cristatus (MK346334, NCBI) isolated from Fuzhuan brick tea and its main purified fraction (EPSs-2) were investigated. Using the RAW264.7 cell model, EPSs-2 exhibited an excellent immunomodulatory effect in vitro. Then, the regulating effects of EPSs on immune function and gut microbiota were evaluated using a cyclophosphamide (Cy)-induced mice model. It was found that both CEPSs and EPSs-2 improved the body weight loss, immune organ indexes as well as the levels of TNF-α, IL-1β, IFN-γ and IgA, exhibiting potent immunoregulatory activity. Moreover, CEPSs and EPSs-2 not only attenuated the intestinal tissue damage, but also promoted the production of short-chain fatty acids and modulated the microbial composition by increasing the growth of Muribaculaceae, Prevotellaceae_UCG-001, Bacteroides, Parabacteroides and Tidjanibacter, while decreasing the relative abundances of Helicobacter, Bilophila, Mucispirillum, Lachnospiraceae, Ruminococcaceae and Clostridiales. These results indicated that the EPSs, especially EPSs-2, exhibited immunomodulatory activity associated with the modulation of gut microbiota to maintain gut homeostasis, which provided evidence for the development of novel potential prebiotics and immunomodulators.

Insight into effects of isolated Eurotium cristatum from Pingwu Fuzhuan brick tea on the fermentation process and quality characteristics of Fuzhuan brick tea

BACKGROUND

Pingwu Fuzhuan brick tea is a type of post-fermented tea manufactured from leaves of the tea plant, Camellia sinensis var. sinensis, the quality of which is influenced by numerous factors, especially microorganisms. Currently, there is little research on the effect of microorganisms on the fermentation and quality characteristics of Pingwu Fuzhuan brick tea. Investigation of the main fungus in this tea and its effect on the fermentation process and tea quality can provide insights into the manufacturing of 'western road' border-selling tea and could lay the foundation for the popularization of Pingwu Fuzhuan brick tea.

RESULTS

The main 'golden flower fungus' in Pingwu Fuzhuan brick tea was isolated and identified as Eurotium cristatum (GenBank accession number: MF800948.1; strain PW-1). Compared with natural fermentation, PW-1 inoculated fermentation accelerated biotransformation of phenolic compounds, which provided tea samples with better taste and tea infusion color. The proportions of velvety and sweet-tasting amino acids increased after 16-day fermentation with PW-1. Alcohols were the most abundant volatiles, with 40.13% and 39.43% content in NF16d and IF16d tea samples, respectively. Orthogonal partial least-squares discriminant analysis (OPLS-DA) and hierarchical clustering analysis (HCA) further revealed that naturally fermented and PW-1 fermented teas were significantly different.

CONCLUSION

Strain PW-1 plays an important role in the fermentation process of Fuzhuan brick tea. Considering fermentation efficiency and tea quality, fermentation inoculated with E. cristatum PW-1 can be applied in the manufacturing of 'western road' border-selling tea. © 2020 Society of Chemical Industry.

Sequencing and phylogenetic analysis of mitochondrial genome of Aspergillus cristatus

Aspergillus cristatus are the dominantly present microorganisms in dark tea. The whole mitochondrial genome sequence of A. cristatus was sequenced and reported in this study. The mitochondrial genome in A. cristatushas a full length of 77,649 bp, which is reported to be the longest among the mitochondrial genomes of Aspergillus species. The basesincluding A (34.14％), T (37.64％), C (15.61％) and G (12.61％) are found in their genome. A total of 42 genes (15 protein-coding genes, lrRNA/srRNA and 25 tRNAs) are encoded by the mitochondrial genome of this fungus. Phylogenetic analysis showed a closest relationship betweenA. pseudoglaucusand the taxonomic status of A. cristatus.

Correlation analysis between filamentous fungi and chemical compositions in a pu-erh type tea after a long-term storage

Storage environment caused the difference between Jinhua Pu-erh tea (JPT) and General Pu-erh tea. In this study, fungal flora and chemical compositions were analyzed. The results showed that storage environment caused significant (p < .05) differences of theaflavins (TF), theabrownins (TB), tea polyphenols (TP), and water-soluble sugars (WSS), and a highly significant (p < .01) difference of thearubigins (TR). Aspergillus niger, Aspergillus pallidofulvus, Aspergillus sesamicola, Penicillium manginii, and Aspergillus tamarii were isolated from Pu-erh teas and identified based on colony characteristics and ITS, β-tubulin, and calmodulin gene sequences, respectively. A. pallidofulvus, A. sesamicola, and P. manginii were dominant fungi in JPT and generated macroscopic yellow cleistothecia after a long-term storage. Correlation analysis showed that dominant fungi exhibited significantly (p < .05 or p < .01) positive or negative corrections with TF, TB, TP, WSS, TR, and gallic acid. This study revealed dominant fungi including A. pallidofulvus, A. sesamicola, and P. manginii and their effects on given chemical compositions.

Purified fraction of polysaccharides from Fuzhuan brick tea modulates the composition and metabolism of gut microbiota in anaerobic fermentation in vitro

One purified fraction from crude Fuzhuan brick tea polysaccharides (FBTPS), FBTPS-3, was obtained through column chromatography of DEAE Sepharose Fast Flow. The chemical properties and probiotic effects of FBTPS-3 were evaluated by fermentation in vitro. Moreover, the effects of FBTPS-3 on the function and metabolic pathway of gut microbiota were investigated by metagenomic sequencing. The results showed that FBTPS-3 was an heteropolysaccharide with molecular weight of 741 kDa, which was mainly composed of Man, Rha, GalA, Gal and Ara in molar ratio of 8.7:15.5:42.2:19.7:13.9. The contents of carbohydrates and uronic acid in FBTPS-3 were 44.78 ± 2.85% and 40.4 ± 2.11%, respectively. After fermentation, the molecular weight of FBTPS-3 and content of carbohydrates were significantly decreased, indicating that FBTPS-3 could be utilized by gut microbiota. Furthermore, the relative abundances of Bacteroides, Megasphaera and Prevotella were significantly increased by FBTPS-3. FBTPS-3 also significantly promoted the production of acetic, propionic and n-butyric acids. Based on the metagenomic sequencing, it was found that FBTPS-3 significantly enriched the metabolic pathway of starch and sucrose. All the results suggest that FBTPS-3 is expected to be developed as functional ingredients or foods to improve the host health through regulating the gut microbiota and physiological metabolic functions.

Eurotium cristatum, a potential probiotic fungus from Fuzhuan brick tea, alleviated obesity in mice by modulating gut microbiota

Obesity is one of the major public health problems worldwide, mainly resulting from unhealthy lifestyles and diet. Gut microbiota dysbiosis may lead to obese humans and animals. Modulating gut bacteria through probiotics or certain dietary supplements could normalize gut microbiota and subsequently alleviate obesity. The daily consumption of Fuzhuan brick tea (FBT) or its extracts has been observed to alleviate obesity in humans and experimental animals. In this study, high-fat diet (HFD)-induced obesity in mice, such as body weight gain and fat accumulation, was prevented by the consumption of Eurotium cristatum, the dominant fungus during the manufacturing and storage of FBT. The dysbiosis of gut microbiota in C57BL/6J mice was also partially normalized. E. cristatum was able to modulate both gut fungal and bacterial compositions, based on the analysis of the microbiota composition of mice fecal samples (n = 5). E. cristatum increased acetate and butyrate-producing bacteria in mouse gut. There was five times more butyrate in the fecal samples from mice fed with E. cristatum than that from untreated HFD mice. Our results suggest that E. cristatum may be used as a probiotic fungus to alleviate obesity and to modulate gut microbiota in humans beneficially.

Complete mitochondrial genome sequence of a xerophilic fungus, Aspergillus pseudoglaucus

Aspergillus pseudoglaucus is a xerophilic filamentous fungus which can produce various secondary metabolites. Here, we reported the complete mitochondrial genome sequence of A. pseudoglaucus isolated from Meju, a soybean brick in Korea. Its mitochondrial genome was successfully assembled from raw reads sequenced using MiSeq by Velvet and SOAPGapCloser. Total length of the mitochondrial genome is 53,882 bp, which is third longest among known Aspergillus mitochondrial genomes and encoded 58 genes (30 protein-coding genes including hypothetical ORFs, two rRNAs, and 26 tRNAs). Nucleotide sequence of coding regions takes over 66.6% and overall GC content is 27.8%. Phylogenetic trees present that A. pseudoglaucus is located outside of section Nidulantes. Additional researches will be required for clarifying phylogenetic position of section Aspergillus.

Recycling of Chinese herb residues by endophytic and probiotic fungus Aspergillus cristatus CB10002 for the production of medicinal valuable anthraquinones

Background

The global prevalence of traditional Chinese medicine stimulates the prosperous development of herb medicines, but the annual generation of massive herb residues becomes big issues about environmental pollution and waste of resources. Microbes play important roles in the circulation of substances in nature, and endophytes represent an underexplored microbial resource possessing the unique symbiotic relationship with plants, not only for discovery of secondary metabolites, but also for potential green recycling of herb residues.

Results

The recycling capacities of several endophytic strains were respectively evaluated via solid state fermentation with herb residues of commercial Huazhenghuisheng oral-liquid (HOL). Among them, Aspergillus cristatus CB10002, a probiotic fungus isolated from Chinese Fu-brick tea, was competent to recycle HOL residues for the production of medicinal valuable anthraquinones, in which four of them, especially citreorosein with significant anti-obesity activity, were first discovered in A. cristatus. Subsequent quantitative analysis showed that about 2.0 mg/g citreorosein and 7.5 mg/g total anthraquinones could be obtained after 35-day fermentation, which was very competitive and economically beneficial. Further nutritional comparisons also revealed that the recycling process indeed ameliorated the nutrients of HOL residues, and thus proposed a possibility to directly dispose the final leftovers as a compost organic fertilizer.

Conclusions

The endophytic and probiotic fungus A. cristatus CB10002 isolated from Chinese Fu-brick tea was screened out to effectively reutilize HOL residues for the production of nine medicinal valuable anthraquinones, whose biosynthesis may be regulated by the induction of HOL residues. The competitive yields of these anthraquinones, as well as the certain composting properties of final leftovers, have made the microbial recycling of HOL residues economically beneficial. Our work demonstrated a promising applied potential of A. cristatus in reutilization of herb residues, and provided a practical strategy for sustainable and value-added microbial recycling of herb residues.

Electronic supplementary material

The online version of this article (10.1186/s12934-019-1150-9) contains supplementary material, which is available to authorized users.

Comparative proteomic analysis reveals the regulatory network of the veA gene during asexual and sexual spore development of Aspergillus cristatus

Aspergillus cristatus is the predominant fungal population during fermentation of Chinese Fuzhuan brick tea, and belongs to the homothallic fungal group that undergoes a sexual stage without asexual conidiation under hypotonic conditions, while hypertonic medium induces initiation of the asexual stage and completely blocks sexual development. However, the veA deletion mutant only produces conidia in hypotonic medium after a 24-h culture, but both asexual and sexual spores are observed after 72 h. The veA gene is one of the key genes that positively regulates sexual and negatively regulates asexual development in A. cristatus. To elucidate the molecular mechanism of how VeA regulates asexual and sexual spore development in A. cristatus, 2D electrophoresis (2-DE) combined with MALDI-tandem ToF MS analysis were applied to identify 173 differentially expressed proteins (DEPs) by comparing the agamotype (24 h) and teleomorph (72 h) with wild-type (WT) A. cristatus strains. Further analysis revealed that the changed expression pattern of Pmk1-MAPK and Ser/Thr phosphatase signaling, heat shock protein (Hsp) 90 (HSP90), protein degradation associated, sulphur-containing amino acid biosynthesis associated, valine, leucine, isoleucine, and arginine biosynthesis involved, CYP450 and cytoskeletal formation associated proteins were involved in the production of conidia in agamotype of A. cristatus. Furthermore, the deletion of veA in A. cristatus resulted in disturbed process of transcription, translation, protein folding, amino acid metabolism, and secondary metabolism. The carbohydrate and energy metabolism were also greatly changed, which lied in the suppression of anabolism through pentose phosphate pathway (PPP) but promotion of catabolism through glycolysis and tricarboxylic acid (TCA) cycle. The energy compounds produced in the agamotype were mainly ATP and NADH, whereas they were NADPH and FAD in the teleomorph. These results will contribute to the existing knowledge on the complex role of VeA in the regulation of spore development in Aspergillus and provide a framework for functional investigations on the identified proteins.

Biochemical Components Associated With Microbial Community Shift During the Pile-Fermentation of Primary Dark Tea

Primary dark tea is used as raw material for compressed dark tea, such as Fu brick tea, Hei brick tea, Hua brick tea, and Qianliang tea. Pile-fermentation is the key process for the formation of the characteristic properties of primary dark tea, during which the microorganism plays an important role. In this study, the changes of major chemical compounds, enzyme activities, microbial diversity, and their correlations were explored during the pile-fermentation process. Our chemical and enzymatic analysis showed that the contents of the major compounds were decreased, while the activities of polyphenol oxidase, cellulase, and pectinase were increased during this process, except peroxidase activity that could not be generated from microbial communities in primary dark tea. The genera Cyberlindnera, Aspergillus, Uwebraunia, and Unclassified Pleosporales of fungus and Klebsiella, Lactobacillus of bacteria were predominant in the early stage of the process, but only Cyberlindnera and Klebsiella were still dominated in the late stage and maintained a relatively constant until the end of the process. The amino acid was identified as the important abiotic factor in shaping the microbial community structure of primary dark tea ecosystem. Network analysis revealed that the microbial taxa were grouped into five modules and seven keystone taxa were identified. Most of the dominant genera were mainly distributed into module III, which indicated that this module was important for the pile-fermentation process of primary dark tea. In addition, bidirectional orthogonal partial least squares (O2PLS) analysis revealed that the fungi made more contributions to the formation of the characteristic properties of primary dark tea than bacteria during the pile-fermentation process. Furthermore, 10 microbial genera including Cyberlindnera, Aspergillus, Eurotium, Uwebraunia, Debaryomyces, Lophiostoma, Peltaster, Klebsiella, Aurantimonas, and Methylobacterium were identified as core functional genera for the pile-fermentation of primary dark tea. This study provides useful information for improving our understanding on the formation mechanism of the characteristic properties of primary dark tea during the pile-fermentation process.

The role of the veA gene in adjusting developmental balance and environmental stress response in Aspergillus cristatus

veA belongs to the velvet regulatory system that regulates the development and secondary metabolism of many fungi. To identify the function of veA in Aspergillus cristatus, veA deletion mutants were constructed by homologous recombination via Agrobacterium tumefaciens-mediated transformation. Deletion of veA led to increased conidial production and reduced sexual sporulation. The regulatory role of veA in A. cristatus was not light-dependent, and this differed from its role in other Aspergilli. Furthermore, veA deletion mutants were more sensitive to environmental stressors, including salt, osmotic pressure, temperature and pH. In contrast, deletion of veA resulted in increased resistance to oxidative stress. veA also affected aerial vegetative growth. Transcriptomic analysis of the veA-null mutant and wild type indicated that most asexual and sexual development genes were upregulated and downregulated, respectively. These findings confirmed that veA has a positive effect on sexual development but represses conidial formation. Overall, these results suggested that the veA gene plays a critical role in maintaining a developmental balance between asexual and sexual sporulation and is involved in vegetative growth and environmental stress response in A. cristatus.

Comparative transcriptome analysis of the calcium signaling and expression analysis of sodium/calcium exchanger in Aspergillus cristatus

Aspergillus cristatus develops into various stages under different Na concentrations: the sexual stage in 0.5 M NaCl and asexual development stage in 3 M NaCl. In order to explore whether the Ca²⁺ signaling pathway in A. cristatus responded to the changes in the salt stress, we analyzed the gene expression levels in A. cristatus respectively cultured in 0.5 M NaCl and 3 M NaCl. According to the BLAST analysis results, we identified 25 Ca²⁺ -signaling proteins in A. cristatus. The expression levels of most genes involved in the Ca²⁺ -signaling pathway in A. cristatus cultured in different salt concentrations showed significant differences, indicating that the Ca²⁺ signaling pathway was involved in the response to the changes in the salt stress. In yeasts, only calcium ion influx proteins were reported to be involved in the response to the changes in the salt stress. So far, the protein for the exchanger of calcium/sodium ions has not been reported. Therefore, we obtained the sodium/calcium exchanger (termed NCX) proteins from the KEGG Database. The ncx gene of A. cristatus was cloned and characterized. The full length of ncx gene is 3055 bp, including a 2994-bp open reading frame encoding 994 amino acids. The expression levels of ncx in the sexual development stage and asexual development stage were respectively ∼8.94 times and ∼2.57 times of that in the hyphal formation stage. Therefore, we suggested that ncx gene was up-regulated to resist the sodium stress. The study results provide the basis for further exploring the Ca²⁺ -signaling mechanism and ion exchanger mechanism.

Evidence-based gene models for structural and functional annotations of the oil palm genome

Background

Oil palm is an important source of edible oil. The importance of the crop, as well as its long breeding cycle (10-12 years) has led to the sequencing of its genome in 2013 to pave the way for genomics-guided breeding. Nevertheless, the first set of gene predictions, although useful, had many fragmented genes. Classification and characterization of genes associated with traits of interest, such as those for fatty acid biosynthesis and disease resistance, were also limited. Lipid-, especially fatty acid (FA)-related genes are of particular interest for the oil palm as they specify oil yields and quality. This paper presents the characterization of the oil palm genome using different gene prediction methods and comparative genomics analysis, identification of FA biosynthesis and disease resistance genes, and the development of an annotation database and bioinformatics tools.

Results

Using two independent gene-prediction pipelines, Fgenesh++ and Seqping, 26,059 oil palm genes with transcriptome and RefSeq support were identified from the oil palm genome. These coding regions of the genome have a characteristic broad distribution of GC₃ (fraction of cytosine and guanine in the third position of a codon) with over half the GC₃-rich genes (GC₃ ≥ 0.75286) being intronless. In comparison, only one-seventh of the oil palm genes identified are intronless. Using comparative genomics analysis, characterization of conserved domains and active sites, and expression analysis, 42 key genes involved in FA biosynthesis in oil palm were identified. For three of them, namely EgFABF, EgFABH and EgFAD3, segmental duplication events were detected. Our analysis also identified 210 candidate resistance genes in six classes, grouped by their protein domain structures.

Conclusions

We present an accurate and comprehensive annotation of the oil palm genome, focusing on analysis of important categories of genes (GC₃-rich and intronless), as well as those associated with important functions, such as FA biosynthesis and disease resistance. The study demonstrated the advantages of having an integrated approach to gene prediction and developed a computational framework for combining multiple genome annotations. These results, available in the oil palm annotation database (http://palmxplore.mpob.gov.my), will provide important resources for studies on the genomes of oil palm and related crops.

Reviewers

This article was reviewed by Alexander Kel, Igor Rogozin, and Vladimir A. Kuznetsov.

Electronic supplementary material

The online version of this article (doi:10.1186/s13062-017-0191-4) contains supplementary material, which is available to authorized users.

Fungal community succession and major components change during manufacturing process of Fu brick tea

Fu brick tea is a unique post-fermented tea product which is fermented with microorganism during the manufacturing process. Metabolic analysis showed that most metabolites content were decreased during the manufacturing process of Fu brick tea, except GA (gallic acid). Illumina MiSeq sequencing of ITS gene amplicons was applied to analyze the fungal community succession. The genera Aspergillus, Cyberlindnera and Candida were predominant at the early stage of manufacturing process (from "primary dark tea" to "fermentation for 3 days"), but after the stage of "fermentation for 3 days" only Aspergillus was still dominated, and maintain a relatively constant until to the end of manufacturing process. The effects of metabolites on the structure of the fungal community were analyzed by redundancy analysis (RDA) and variation partitioning analysis (VPA). The results indicated that GCG (gallocatechin gallate), EGCG (epigallocatechin gallate) and GA as well as the interactions among them were the most probably ones to influence, or be influenced by the fungal communities during the fermentation process of Fu brick tea. This study revealed fungal succession, metabolite changes and their relationships, provided new insights into the mechanisms for manufacturing process of Fu brick tea.

Comparative Transcriptome Sequence Analysis of Sporulation-Related Genes of Aspergillus cristatus in Response to Low and High Osmolarity

Aspergillus cristatus undergoes sexual and asexual development under conditions of low and high osmotic pressure, respectively. In this study, the expression levels of 107 genes associated with sexual and asexual development were analysed under conditions of low and high osmotic pressure by RNA sequencing. The results showed that 37 genes were up-regulated and other genes were down-regulated under conditions of high osmotic pressure, with most of the up-regulated genes associated with asexual development and most down-regulated genes associated with sexual development. These results suggest that osmotic pressure regulated sexual and asexual development of A. cristatus by controlling the expression levels of key genes. Meanwhile, there were differences in the expression levels of key genes associated with the regulation of sexual and asexual development between A. cristatus and Aspergillus nidulans. Moreover, we verified the reliability of the results by quantitative real-time polymerase chain reaction analysis of some key genes. In this study, the relationship between sporulation-related genes and osmotic pressure at the transcriptome level were analysed, which indicated that A. cristatus was a useful model organism for the study of osmotic pressure regulation on sexual and asexual development.