A Beauveria phylogeny inferred from nuclear ITS and EF1- sequences: evidence for cryptic diversification and links to Cordyceps teleomorphs

Beauveria is a globally distributed genus of soil-borne entomopathogenic hyphomycetes of interest as a model system for the study of entomopathogenesis and the biological control of pest insects. Species recognition in Beauveria is difficult due to a lack of taxonomically informative morphology. This has impeded assessment of species diversity in this genus and investigation of their natural history. A gene-genealogical approach was used to investigate molecular phylogenetic diversity of Beauveria and several presumptively related Cordyceps species. Analyses were based on nuclear ribosomal internal transcribed spacer (ITS) and elongation factor 1-alpha (EF1-alpha) sequences for 86 exemplar isolates from diverse geographic origins, habitats and insect hosts. Phylogenetic trees were inferred using maximum parsimony and Bayesian likelihood methods. Six well supported clades within Beauveria, provisionally designated A-F, were resolved in the EF1-alpha and combined gene phylogenies. Beauveria bassiana, a ubiquitous species that is characterized morphologically by globose to subglobose conidia, was determined to be non-monophyletic and consists of two unrelated lineages, clades A and C. Clade A is globally distributed and includes the Asian teleomorph Cordyceps staphylinidaecola and its probable synonym C. bassiana. All isolates contained in Clade C are anamorphic and originate from Europe and North America. Clade B includes isolates of B. brongniartii, a Eurasian species complex characterized by ellipsoidal conidia. Clade D includes B. caledonica and B. vermiconia, which produce cylindrical and comma-shaped conidia, respectively. Clade E, from Asia, includes Beauveria anamorphs and a Cordyceps teleomorph that both produce ellipsoidal conidia. Clade F, the basal branch in the Beauveria phylogeny includes the South American species B. amorpha, which produces cylindrical conidia. Lineage diversity detected within clades A, B and C suggests that prevailing morphological species concepts underestimate species diversity within these groups. Continental endemism of lineages in B. bassiana s.l. (clades A and C) indicates that isolation by distance has been an important factor in the evolutionary diversification of these clades. Permutation tests indicate that host association is essentially random in both B. bassiana s.l. clades A and C, supporting past assumptions that this species is not host specific. In contrast, isolates in clades B and D occurred primarily on coleopteran hosts, although sampling in these clades was insufficient to assess host affliation at lower taxonomic ranks. The phylogenetic placement of Cordyceps staphylinidaecola/bassiana, and C. scarabaeicola within Beauveria corroborates prior reports of these anamorph-teleomorph connections. These results establish a phylogenetic framework for further taxonomic, phylogenetic and comparative biological investigations of Beauveria and their corresponding Cordyceps teleomorphs.

On the relationships of Paecilomyces sect. Isarioidea species

Phylogenetic relationships of Paecilomyces sect. Isarioidea species were analysed using the beta-tubulin gene and ITS rDNA. Maximum parsimony analyses showed that the section does not form a natural taxonomic group and is polyphyletic within the Hypocreales. However, a group was recognized, designated as the Isaria clade, to be monophyletic comprising of the following Paecilomyces species: P. amoeneroseus, P. cateniannulatus, P. cateniobliquus, P. cicadae, P. coleopterorus, P. farinosus, P. fumosoroseus, P. ghanensis, P. javanicus and P. tenuipes. Some of these species have teleomorphs in Cordyceps.

Novel blastospore-based transformation system for integration of phosphinothricin resistance and green fluorescence protein genes into Beauveria bassiana

A novel system was developed for efficient transformation of the fungal biocontrol agent Beauveria bassiana. Competent blastospores were prepared and stored in LiAc- and glycerol-inclusive suspension at -76 degrees C for sequential use in transformation. The system was successfully applied to integrating phosphinothricin resistance gene bar and enhanced green fluorescence protein gene egfp into B. bassiana via blastospore absorption of a plasmid vectoring bar and egfp. A frequency of 24 transformants per microgram of DNA was achieved. The blastospore-based transformation system has proven to be very convenient and would be highly potential for use in genetic manipulation of B. bassiana and other filamentous species.

Anti-inflammatory principles from Cordyceps sinensis

In order to explore the anti-inflammatory principles of the mycelia of Cordyceps sinensis, the crude extract and partially purified fractions were examined for their inhibition of superoxide anion generation and elastase release. Further chemical investigation of the bioactive fractions has resulted in the identification of 50 compounds, including five constituents, cordysinins A-E (1-5), reported from a natural source for the first time. In addition, compounds were examined for their anti-inflammatory activity. 1-(5-Hydroxymethyl-2-furyl)-β-carboline displayed the most significant inhibition of superoxide anion generation and elastase release with IC50 values of 0.45±0.15 and 1.68±0.32 μM, respectively.

EST analysis of cDNA libraries from the entomopathogenic fungus Beauveria (Cordyceps) bassiana. I. Evidence for stage-specific gene expression in aerial conidia, in vitro blastospores and submerged conidia

The entomopathogenic fungus Beauveria (Cordyceps) bassiana holds much promise as a pest biological control agent. B. bassiana produces at least three in vitro single cell infectious propagules, including aerial conidia, vegetative cells termed blastospores and submerged conidia, that display different morphological, biochemical and virulence properties. Populations of aerial conidia, blastospores and submerged conidia were produced on agar plates, rich liquid broth cultures and under conditions of nutrient limitation in submerged cultures, respectively. cDNA libraries were generated from mRNA isolated from each B. bassiana cell type and approximately 2,500 5' end sequences were determined from each library. Sequences derived from aerial conidia clustered into 284 contigs and 963 singlets, with those derived from blastospores and submerged conidia forming 327 contigs with 788 singlets, and 303 contigs and 1,079 contigs, respectively. Almost half (40-45 %) of the sequences in each library displayed either no significant similarity (e value >10(-4)) or similarity to hypothetical proteins found in the NCBI database. The expressed sequence tag dataset also included sequences representing a significant portion of proteins in cellular metabolism, information storage and processing, transport and cell processes, including cell division and posttranslational modifications. Transcripts encoding a diverse array of pathogenicity-related genes, including proteases, lipases, esterases, phosphatases and enzymes producing toxic secondary metabolites, were also identified. Comparative analysis between the libraries identified 2,416 unique sequences, of which 20-30 % were unique to each library, and only approximately 6 % of the sequences were shared between all three libraries. The unique and divergent representation of the B. bassiana transcriptome in the cDNA libraries from each cell type suggests robust differential gene expression profiles in response to environmental conditions.

Genome-wide transcriptome and proteome analysis on different developmental stages of Cordyceps militaris

BACKGROUND

Cordyceps militaris, an ascomycete caterpillar fungus, has been used as a traditional Chinese medicine for many years owing to its anticancer and immunomodulatory activities. Currently, artificial culturing of this beneficial fungus has been widely used and can meet the market, but systematic molecular studies on the developmental stages of cultured C. militaris at transcriptional and translational levels have not been determined.

METHODOLOGY/PRINCIPAL FINDINGS

We utilized high-throughput Illumina sequencing to obtain the transcriptomes of C. militaris mycelium and fruiting body. All clean reads were mapped to C. militaris genome and most of the reads showed perfect coverage. Alternative splicing and novel transcripts were predicted to enrich the database. Gene expression analysis revealed that 2,113 genes were up-regulated in mycelium and 599 in fruiting body. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed to analyze the genes with expression differences. Moreover, the putative cordycepin metabolism difference between different developmental stages was studied. In addition, the proteome data of mycelium and fruiting body were obtained by one-dimensional gel electrophoresis (1-DGE) coupled with nano-electrospray ionization liquid chromatography tandem mass spectrometry (nESI-LC-MS/MS). 359 and 214 proteins were detected from mycelium and fruiting body respectively. GO, KEGG and Cluster of Orthologous Groups (COG) analysis were further conducted to better understand their difference. We analyzed the amounts of some noteworthy proteins in these two samples including lectin, superoxide dismutase, glycoside hydrolase and proteins involved in cordycepin metabolism, providing important information for further protein studies.

CONCLUSIONS/SIGNIFICANCE

The results reveal the difference in gene expression between the mycelium and fruiting body of artificially cultivated C. militaris by transcriptome and proteome analysis. Our study provides an effective resource for the further developmental and medicinal research of this promising fungus.

Degradation of 1,4-dioxane and cyclic ethers by an isolated fungus

By using 1,4-dioxane as the sole source of carbon, a 1,4-dioxane-degrading microorganism was isolated from soil. The fungus, termed strain A, was able to utilize 1,4-dioxane and many kinds of cyclic ethers as the sole source of carbon and was identified as Cordyceps sinensis from its 18S rRNA gene sequence. Ethylene glycol was identified as a degradation product of 1,4-dioxane by the use of deuterated 1,4-dioxane-d8 and gas chromatography-mass spectrometry analysis. A degradation pathway involving ethylene glycol, glycolic acid, and oxalic acid was proposed, followed by incorporation of the glycolic acid and/or oxalic acid via glyoxylic acid into the tricarboxylic acid cycle.

EST analysis of cDNA libraries from the entomopathogenic fungus Beauveria (Cordyceps) bassiana. II. Fungal cells sporulating on chitin and producing oosporein

In the accompanying paper [Cho, E.-M., Liu, L., Farmerie, W. & Keyhani, N. O. (2006). Microbiology 152, 2843-2854], the analysis of expressed sequence tag (EST) libraries derived from homogeneous single-cell populations of aerial conidia, in vitro blastospores and submerged conidia of the entomopathogenic fungus Beauveria (Cordyceps) bassiana has been reported. Here an extended EST analysis is presented of complex cell mixtures derived from fungal cells sporulating on chitin or grown under culture conditions inducing the production of the B. bassiana secondary metabolite, oosporein. Fungal material used for the construction of the libraries included germinating conidia and blastospores, mycelia, as well as cells in various developmental stages. Approximately 2,500 5' end sequences were determined from random sequencing of clones from each library, and were clustered into 277 contigs with 1,069 singlets, and 306 contigs with 1,064 singlets, for the chitin and oosporein libraries, respectively. Almost half (45-50 %) of the sequences in each library displayed either no significant similarity (e value >10(-4)) or similarity to hypothetical proteins found in the NCBI database. Approximately 20-25 % of the sequences in each library could be annotated by gene ontology terms. A comparative analysis between the two libraries, as well as the libraries in the accompanying paper, is presented. A set of 4,360 clustered and unique sequences was characterized. The data are indicative of a highly plastic gene expression repertoire being available to B. bassiana for growth during different environmental and developmental conditions, and provides a dataset for gene discovery and genome annotation.

Morphological and genetic characterization of a cultivated Cordyceps sinensis fungus and its polysaccharide component possessing antioxidant property in H22 tumor-bearing mice

Cordyceps sinensis, one of the most precious traditional Chinese medicines, possesses the antitumor activity, antioxidant activity and the capability of modulating the immune system. In the present study, a fungus strain G1 isolated from wild C. sinensis was identified and initially characterized. A phylogenetic tree was generated based on the sequences of the internal transcribed spacer (ITS) region of related fungi. The analysis of ITS sequence showed that fungus G1 was clustered together with C. sinensis, Tolypocladium cylindrosporum and Tolypocladium inflatum in the phylogenetic tree. Both the morphological character and the ITS sequence analysis establish that fungus G1 is one of the anamorph strains of C. sinensis and belongs to Tolypocladium genus. Furthermore, the polysaccharide (PS) extracted from fungus G1 and its antioxidant activity on H22-bearing mice was investigated. H22 cells were hypodermically injected into the right oxter of each mouse after the ICR mice were treated with PS by means of gavage for 7 days. Then the same administration process continued for 9 days. At the end of the experiments, the tumor weight of each mouse was measured. Superoxide dismutase (SOD) activity and malondialdehyde (MDA) level in mouse liver, brain and serum, as well as glutathione peroxidase (GSH-Px) activity in mouse liver and brain were assayed. The results showed that the H22 tumor growth was significantly inhibited by PS. Moreover, PS significantly enhanced SOD activity of liver, brain and serum as well as GSH-Px activity of liver and brain in tumor-bearing mice. PS also significantly reduced the level of MDA in liver and brain of tumor-bearing mice.

Efficient genome editing in filamentous fungi via an improved CRISPR-Cas9 ribonucleoprotein method facilitated by chemical reagents

DNA double-strand break (DSB) repair induced by the RNA-programmed nuclease Cas9 has become a popular method for genome editing. Direct genome editing via Cas9-CRISPR gRNA (guide RNA) ribonucleoprotein (RNP) complexes assembled in vitro has also been successful in some fungi. However, the efficiency of direct RNP transformation into fungal protoplasts is currently too low. Here, we report an optimized genome editing approach for filamentous fungi based on RNPs facilitated by adding chemical reagents. We increased the transformation efficiency of RNPs significantly by adding Triton X-100 and prolonging the incubation time, and the editing efficiency reached 100% in Trichoderma reesei and Cordyceps militaris. The optimized RNP-based method also achieved efficient (56.52%) homologous recombination integration with short homology arms (20 bp) and gene disruption (7.37%) that excludes any foreign DNA (selection marker) in T. reesei. In particular, after adding reagents related to mitosis and cell division, the further optimized protocol showed an increased ratio of edited homokaryotic transformants (from 0% to 40.0% for inositol and 71.43% for benomyl) from Aspergillus oryzae, which contains multinucleate spores and protoplasts. Furthermore, the multi-target engineering efficiency of the optimized RNP transformation method was similar to those of methods based on in vivo expression of Cas9. This newly established genome editing system based on RNPs may be widely applicable to construction of genome-edited fungi for the food and medical industries, and has good prospects for commercialization.

Characterization of (R)-selective amine transaminases identified by in silico motif sequence blast

Compared to (S)-selective amine transaminase ((S)-AT), the (R)-selective counterpart ((R)-AT) has been less studied. As such, a simplified "Motif Sequence Blast" search (Höhne et al. Nat Chem Biol 6:807-813, 2010) was carried out to identify new (R)-ATs from the protein databases. The combined conserved sequence motifs of (R)-ATs based on the previous in silico method of predicting (R)-selective amine transaminase were used as the template sequence for BLASTP search at default settings in NCBI, and six candidate sequences were identified. These putative (R)-AT genes were synthesized and overexpressed in Escherichia coli. Among them, five new (R)-ATs were expressed as soluble protein and showed unusual substrate specificity and high stereoselectivity. Furthermore, several unnatural amino acids, such as D-alanine, D-2-aminobutyric acid, and D-norvaline, were synthesized via the (R)-AT-catalyzed amino transfer reaction to the corresponding keto acids. Optically pure (S)-amines were also obtained by kinetic resolution of racemic amines catalyzed with these new (R)-ATs. Therefore, the Motif Sequence Blast search offers a quick and effective method for in silico identification of new (R)-ATs, and the newly identified (R)-ATs are attractive additions to the toolbox of (R)-ATs for further study and industrial application.

Towards a phylogenetic classification of Cordyceps: ITS nrDNA sequence data confirm divergent lineages and paraphyly

The ascomycetous genus Cordyceps accommodates endoparasitic species that attack arthropods or other fungi. Analyses of ITS nrDNA sequence data of 72 taxa from the teleomorph genera Cordyceps, Claviceps, Epichloë, and the anamorph genera Akanthomyces, Beauveria, Metarhizium, Hirsutella, Hymenostilbe, Paecilomyces, Polycephalomyces, and Tolypocladium assigned the taxa to four main evolutionary lineages not reflected in the current classification of Cordyceps. Ten subclades were recognized from separate analyses of data subsets. Judged from the ITS phylogenies, Cordyceps spp. with branched stromata were highly supported as a divergent lineage. Host specificity was found to be of limited phylogenetic significance, and several host shifts are suggested to have occurred during the evolution of Cordyceps. Similar ascospore morphology was not reflected in the phyletic groups, and closely related taxa showed large interspecific variation with respect to the number of segments in which the ascospores are divided. However, combinations of selected characters were found to delimitate some lineages, e.g. all Cordyceps spp. that attack hosts in the insect orders Coleoptera and Lepidoptera, and with non-immersed perithecia and clavate to acicular, brightly yellowish to reddish stromata, constituted a separate clade. Furthermore, all Cordyceps spp. with perithecia obliquely immersed in the stroma were recognized as a distinct monophyletic group. This clade is additionally characterized by the formation of anamorphs ascribable to the genus Hymenostilbe. The mycogenous Cordyceps spp. grouped in a separate subclade, interspersed by two cicadaen parasites and all Tolypocladium spp. except T. parasiticum. Tolypocladium and Beauveria were found to be polyphyletic. The included Claviceps and Epichloë taxa appeared to be derived within Cordyceps, thus making Cordyceps paraphyletic as suggested in other studies.

Transcriptome-wide analysis reveals the progress of Cordyceps militaris subculture degeneration

BACKGROUND

The entomopathogenic mushroom Cordyceps militaris is an important medicinal and food resource owing to its various medicinal components and pharmacological effects. However, the high frequency of strain degeneration during subculture seriously restricts the large-scale production of C. militaris, and the mechanism underlying strain degeneration remains unclear. In this study, we artificially cultured C. militaris for six generations and compared changes during fruiting body growth. The transcriptome of six generations of C. militaris strains were sequenced with the Illumine Hiseq4000.

RESULTS

The subcultured C. militaris strains degenerated beginning at the third generation, with incomplete fruiting body growth beginning at the fourth generation. Over 9,015 unigenes and 731 new genes were identified. In addition, 35,323 alternative splicing (AS) events were detected in all samples, and more AS events occurred in the second, fourth and sixth generations. Compared with the first generation, the third generation (degenerated strain) included 2,498 differentially expressed genes (DEGs) including 1,729 up-regulated and 769 down-regulated genes. This number was higher than the number of DEGs in the second (1,892 DEGs), fourth (2,006 DEGs), fifth (2,273 DEGs) and sixth (2,188 DEGs) generations. Validation of RNA-seq by qRT-PCR showed that the expression patterns of 51 DEGs were in accordance with the transcriptome data.

CONCLUSION

Our results suggest that the mechanism of C. militaris strain degeneration is associated with gene involved in toxin biosynthesis, energy metabolism, and DNA methylation and chromosome remodeling.

Structures of the mating-type loci of Cordyceps takaomontana

Nucleotide sequences of the mating-type loci MAT1-1 and MAT1-2 of Cordyceps takaomontana were determined, which is the first such report for the clavicipitaceous fungi. MAT1-1 contains two mating-type genes, MAT1-1-1 and MAT1-1-2, but MAT1-1-3 could not be found. On the other hand, MAT1-2 has MAT1-2-1. A pseudogene of MAT1-1-1 is located next to MAT1-2.

Genetic variation of Cordyceps sinensis, a fruit-body-producing entomopathogenic species from different geographical regions in China

Cordyceps sinensis is one of the most valuable medicinal fungi in the Orient. It is naturally distributed in the eastern extension area of the Qinghai-Tibet plateau, at an altitude over 4000 m high. In order to investigate genetic variation and evolutionary relationships of C. sinensis from different geographical regions, 17 isolates of C. sinensis were collected from different provinces and the complete sequences of rDNA ITS were determined. On the basis of 5.8S rDNA and ITS region analysis, it was clearly shown that the ITS sequences within C. sinensis are highly homologous regardless of geographical origin. The distance values between the sequences in this study were lower than 0.03. This implied that C. sinensis from different geographic regions are the same species; they are not different species or a species complex. The results also showed that distance values between C. sinensis and Hirsutella sinensis are of the same order as those within C. sinensis from different geographic regions. This confirmed our previous results that C. sinensis should only have H. sinensis as its asexual stage whatever the geographic region from which the samples were collected. An rDNA ITS clone library was established to obtain further evidence for the interpretation of the fungal community structure from C. sinensis and to confirm the accuracy of the taxonomic identities produced by directly sequencing the rDNA ITS region. The discrimination between intraspecies of C. sinensis might provide additional data for the authentication of medicinal material at the species or intraspecies level.

Cordyceps militaris induces the IL-18 expression via its promoter activation for IFN-gamma production

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps militaris, one of traditional herbal ingredient in oriental medicine, has been known to promote anticancer and immunomodulatory activities in vitro and in vivo. However, the biological mechanism of anticancer activity has been unknown.

OBJECTIVE

To investigate the effect of Cordyceps militaris extract on expression of interferon gamma (IFN-gamma) through interlukin-18 (IL-18) induction and its biological mechanism in vitro and in vivo.

MATERIALS AND METHODS

Mice were administrated orally with solution extracted from Cordyceps militaris. The transcription level of IL-18 and IFN-gamma production were measured by reverse transcriptase polymerase chain reaction (RT-PCR) and immunohistochemistry. RAW 264.7 cells were transiently transfected with pCATp1 and pCATp2 for IL-18 promoter functional analysis.

RESULTS

Cordyceps militaris extracts treatment significantly induced level of IL-18 transcription in mouse brain and liver and enhanced IL-18 transcription level and activated the IFN-gamma production in RAW 264.7 cells. Furthermore, Cordyceps militaris extract led to increase the activity of pCATp1 construct containing the 5' franking region of IL-18 promoter in RAW 264.7 cells.

CONCLUSION

Cordyceps militaris extract induced IL-18 mRNA level via enhancing of P1 promoter region result in activation of IFN-gamma production, indicating its potential as an immune activator or anticancer drug.

Genome-wide analysis of DNA methylation in the sexual stage of the insect pathogenic fungus Cordyceps militaris

DNA methylation is a basic epigenetic mechanism found in eukaryotes, but its patterns and roles vary significantly among diverse taxa. In fungi, DNA methylation has various effects on diverse biological processes. However, its function in the sexual development of fungi remains unclear. Cordyceps militaris, readily performs sexual reproduction and thus provides a remarkably rich model for understanding epigenetic processes in sexual development. Here, we surveyed the methylome of C. militaris at single-base resolution to assess DNA methylation patterns during sexual development using genomic bisulfite sequencing (BS-Seq). The results showed that approximately 0.4 % of cytosines are methylated, similar to the DNA methylation level (0.39 %) during asexual development. Importantly, we found that DNA methylation in the fungi undergoes global reprogramming during fungal development. Moreover, RNA-Seq analysis indicated that the differentially methylated regions (DMRs) have no correlation with the genes that have roles during fungal sexual development in C. militaris. These results provide a comprehensive characterization of DNA methylation in the sexual development of C. militaris, which will contribute to future investigations of epigenetics in fungi.

Efficient CRISPR/Cas9 system based on autonomously replicating plasmid with an AMA1 sequence and precisely targeted gene deletion in the edible fungus, Cordyceps militaris

Cordyceps militaris is a popular edible fungus with important economic value worldwide. In this study, an efficient CRISPR/Cas9 genome-editing system based on an autonomously replicating plasmid with an AMA1 sequence was constructed. Further, a precisely targeted gene deletion via homology-directed repair was effectively introduced in C. militaris. Gene editing was successful, with efficiencies of 55.1% and 89% for Cmwc-1 and Cmvvd, respectively. Precisely targeted gene deletion was achieved at an efficiency of 73.9% by a single guide RNA supplementation with donor DNAs. Double genes, Cmwc-1 and Cmvvd, were edited simultaneously with an efficiency of 10%. Plasmid loss was observed under non-selective culture conditions, which could permit recycling of the selectable marker and avoid the adverse effects of the CRISPR/Cas9 system on the fungus, which is beneficial for the generation of new cultivars. RNA Pol III promoters, endogenous tRNAPro of C. militaris, and chimeric AfU6-tRNAGly can be used to improve the efficiency. Polyethylene glycol-mediated protoplast transformation was markedly more efficient than Agrobacterium tumefaciens-mediated transformation of C. militaris. To our knowledge, this is the first description of genome editing and precisely targeted gene deletion in mushrooms based on AMA1 plasmids. Our findings will enable the modification of multiple genes in both functional genomics research and strain breeding.

Molecular analysis and biochemical characteristics of degenerated strains of Cordyceps militaris

Cordyceps militaris has commercially been cultivated, but its degenerated subcultures have gradually resulted in the reduced production. In this study, the biological characteristics and DNA change of degenerated strains of C. militaris were analyzed in detail. The results showed that the degenerated strains exhibited the lower growth rate, and the deficiency in fruit body formation and pigment production. The degradation of strains was not attributable to DNA changes identified by RAPD and SRAP. Compared to normal strains, the biochemical indexes of degradation strains and normal strains showed that the carotenoid content of degradation strains was significantly lower, the activities of cellulase and amylase of degradation strains were slight lower, and the EPS content was lower, but the IPS was higher. All these results suggested that the degradation of C. militaris may be caused by the inhibition or in harmony of metabolite synthesis involved in the metabolic regulation, which should be further verified.

Entomogenous fungi that produce 2,6-pyridine dicarboxylic acid (dipicolinic acid)

An inhibitor of the prophenoloxidase activation using extract from a silkworm pupa was isolated from a culture filtrate of Cordyceps militaris and identified as dipicolinic acid (DPA). The production of DPA in Clavicipitaceae fungi was examined. Entomogenous fungi that produce DPA were integrated into one group by a phylogenetic analysis based on 18S rDNA. It is suggested that the group acquired an ability to produce DPA during its evolution from plant pathogenic fungi to entomogenous fungi.

Biological characteristics, bioactive components and antineoplastic properties of sporoderm-broken spores from wild Cordyceps cicadae

BACKGROUND

Cordyceps cicadae, an entomogenous fungus has been used as a dietary therapeutic in traditional Chinese medicine for several millennia, in the form of powders and decoction. However, wild C. cicadae is notably scarce. To date, there is still a lack of comprehensive and deep studies on the biological characteristics, chemical profiles and antineoplastic mechanisms of C. cicadae, especially its spores.

AIM OF THE STUDY

This study aimed to identify wild C. cicadae using rDNA-ITS sequences. Active constituents and volatile ingredients of C. cicadae sporoderm-broken spore powders (CCBSP) were elucidated using UPLC-ESI-Q-TOF-MS and GC-MS, respectively. The underlying anti-neoplastic mechanisms of CCBSP were further investigated in A549 lung carcinoma cells.

RESULTS

Molecular phylogenetic analysis of nuclear rDNA sequences indicated that wild C. cicadae belonged to Paecilomyces cicadae. Eight primary compounds from CCBSP were identified by MS fragmentation ions including nucleosides, cordycepic acid, cordycepin, beauvericin and myriocin. In total, forty-nine volatile components representing 99.56% of CCBSP were clearly identified. CCBSP exhibited antiproliferative effects on A549 cells with IC₅₀ value of 125.54 ± 2.71 µg/ml, blocking the cell cycle in the G2/M phase. The nuclear morphology exhibited typical characteristics of apoptosis by Hoechst fluorescent stain. AnnexinV-FITC/PI staining revealed that the number of apoptotic cells increased after CCBSP treatment. Furthermore, immunofluorescence experiments indicated that CCBSP lowered the expressions of β-catenin and N-cadherin, which was accompanied by repressed Wnt/β-catenin signalling and activation of caspase-mediated apoptosis pathways.

CONCLUSIONS

rDNA-ITS sequencing enabled molecular identification of wild C. cicadae. Importantly, these findings provide the first evidence regarding the full-scale bioactive components and antineoplastic properties of CCBSP. These data highlight the significance of C. cicadae as a potential antineoplastic agent.

Purification and biochemical characterization of a novel fibrinolytic enzyme from culture supernatant of Cordyceps militaris

A novel fibrinolytic enzyme from Cordyceps militaris was produced by submerged culture fermentation, purified, and biochemically characterized. The enzyme was purified to homogeneity, with an overall yield of 4.0% and a specific activity of 1682 U/mg. The molecular weight and pI of the enzyme were 32 kDa and 9.3 ± 0.2, respectively. The optimal pH and temperature of the enzyme were 7.4 and 37 °C, respectively. The enzyme activity was inhibited by Fe(2+), phenylmethane sulfonyl fluoride (PMSF), aprotinin, and pepstatin but not by N-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and ethylenediamine tetracetic acid (EDTA). Three internal peptides of the enzyme, APQALTVAAVGATWAR, EKNVGSTVNLLSYDGNK, and TDATSVLLDGYNVSAVNDLVAK, were obtained. The enzyme could hydrolyze fibrin(ogen) directly and cleave the α-chains more efficiently than β- and γ-chains, suggesting that it is a plasmin like protein. It degraded thrombin, which indicated that it can act as an anticoagulant and prevent thrombosis. Intravascular thrombosis is one of the major reasons of cardiovascular diseases. On the basis of these results, the purified enzyme can be developed as a natural agent for oral fibrinolytic therapy or prevention of thrombosis.

Accelerated nrDNA evolution and profound AT bias in the medicinal fungus Cordyceps sinensis

Cordyceps sinensis is a reputed medicinal fungus growing parasitically on buried larvae of ghost moths in Asian high-altitude grassland ecosystems. We have analysed the intraspecific ITS nrDNA (ITS1, 5.8S gene, ITS2) variation among 71 sequences of C. sinensis available in EMBL/Genbank. The ITS sequences, submitted to Bayesian ML analyses, were distributed into five groups, referred to as A-E. Nine of the sequences (groups D and E) grouped with distantly related hypocrealean/clavicipitalean taxa and are interpreted as sequences erroneously accessioned under wrong taxon names. The remaining 62 sequences constituted three highly supported clades (groups A-C), that may represent cryptic (phylogenetic) species currently ascribed to C. sinensis. A remarkably high sequence divergence occurred in the 5.8S gene between the three groups. Sequences of groups B and C showed accelerated substitution rates and high AT nucleotide bias. We hypothesize that the accelerated evolution and AT bias have been caused by a shift in life historical attributes or ecology. We also suggest that the recorded differences in medicinal effects among C. sinensis populations may be attributed to the existence of genetically differentiated chemotypes in this morphotaxon.

Strain-specific pathogenicity and subversion of phenoloxidase activity in the mosquito Aedes aegypti by members of the fungal entomopathogenic genus Isaria

Development of alternative vector control strategies are becoming more pressing given the rapid evolution of insecticide resistance and the rise of vector borne pathogens affecting public health such as dengue, chikungunya and Zika. Fungal-based biopesticides are promising alternatives to synthetic insecticides because they are ecofriendly and are highly effective at infecting insects through contact. This study evaluated the susceptibility of the yellow fever mosquito Ae. aegypti to a range of entomopathogenic fungal strains from the genus Isaria. We observed a diverse variation in the virulence of the Isaria strains tested, with two strains showing high pathogenicity towards adult mosquitoes. Mosquito susceptibility to fungal infection was further corroborated through the molecular quantification of fungal loads and the transcript evaluation of a fungal-specific pathogen recognition molecule in the mosquito body. Moreover, quantitative analysis of transcript abundance coupled with enzymatic assays revealed strain-specific subversion of the melanization cascade, an important immune response component. Our study contributes critical insights for a better understanding of fungal-mosquito interactions.

Heterothallism in Cordyceps takaomontana

Perithecium formation of an entomopathogenic fungus Cordyceps takaomontana was promoted by treating the mycelia with cell wall-degrading enzymes and PEG 4000. Perithecia were formed in the mixed culture of both mating-type strains MAT1 and MAT2, and not in the culture of MAT1 or MAT2 alone. The MAT1 strains did not possess a mating-type gene MAT1-1-3, but could produce perithecia. These results strongly suggested that C. takaomontana is heterothallic, and does not need MAT1-1-3 for the perithecium formation. MAT1-1-3 was also not found in another entomopathogenic fungus Cordyceps militaris. On the other hand, phytopathogenic fungi Balansia sp., Claviceps purpurea and Epichloë typhina possessed MAT1-1-3. The structures of mating-type locus MAT1-1 of these phytopathogenic fungi in the family Clavicipitaceae were similar to that of a phytopathogenic fungus Gibberella fujikuroi in the family Nectriaceae, which is closely related to Clavicipitaceae. These results suggested that phytopathogen might be more ancestral group than entomopathogen in Clavicipitaceae, and that MAT1-1-3 might be lost in the course of the host shift from plants to insects.