Functional Analysis of Ribonucleotide Reductase from Cordyceps militaris Expressed in Escherichia coli

Genome resequencing and transcriptome analysis reveal the molecular mechanism of albinism in Cordyceps militaris

Light is an important regulator of most fungal life activities and transmits signals through certain photoreceptor proteins such as phytochromes and cryptochromes. However, the light response mechanism varies across different fungi. The WCC complex composed of white collar-1 (WC-1) and white collar-2 (WC-2) is considered to be the key factor regulating fungal albinism. The photoreceptor protein Vivid (VVD) is the negative regulator of the WCC complex. In this study, we discovered an albino mutant (Alb) generated by ⁶⁰Co-γ-ray irradiation from Cordyceps militaris (C. militaris). This mutant showed albinism of the mycelia and fruiting bodies under light, and the fruiting bodies developed normally. However, this phenotype in Alb differed from that in the CmWC-1 mutant. This suggests that CmWC1 may not be mutated in Alb. A mutated polyketide synthase (CmPKS) was found through genome resequencing analysis. CmPKS was significantly induced by a light signal, and its mutation reduced melanin accumulation in C. militaris. In addition, we found that a zinc-finger domain-containing protein (CmWC-3) was induced by a light signal and interacted with CmWC-1 and CmVVD. Moreover, CmWC-2 also interacted with CmWC-1 to form the WCC complex and was inhibited by CmVVD. In addition, CmWC-3 directly bound with the CmPKS promoter, but CmWC1 did not. These results suggest that albinism and fruiting body development are two independent processes; the WCC complex of CmWC-1 with CmWC-3 regulates CmPKS expression to regulate color change, whereas CmWC-1 with CmWC-2 affects fruiting body development via the carotenoid pathway. These findings will help us to better understand the albinism mechanism of C. militaris.

Construction of Cordycepin High-Production Strain and Optimization of Culture Conditions

This study aimed to increase cordycepin production by over-expressing bio-synthetic enzyme genes, including the adenylosuccinate synthase, adenylosuccinate lyase, and 5'-nucleotidase genes. Research data showed that the extracellular and intracellular cordycepin concent of 24 recombinant strains were higher than those of C. militaris WT, indicating that over-expression of key enzyme genes increased cordycepin production. Among them, the CM-adss-5 strain had highest cordycepin production, and the extracellular and intracellular cordycepin concent were 1119.75 ± 1.61 and 65.56 ± 0.97 mg/L, which were 1.26 and 2.61 times that of C. militaris WT. This study also optimized the culture conditions of CM-adss-5 strain through single factor experiments to obtain the best culture conditions. The best culture condition was 25 °C constant temperature, 180-rpm shaking culture, fermentation period 12 days, inoculate amount 5%, initial pH 6, seed age 108 h, and liquid volume 110/250 mL. Then, the extracellular and intracellular cordycepin content of CM-adss-5 strain reached 2581.96 ± 21.07 and 164.08 ± 1.44 mg/L, which were higher by 130.6% and 150.3%, respectively. Therefore, our research provides a way to efficiently produce cordycepin for the development of cordycepin and its downstream products.

Immunostimulatory Activity of Cordyceps militaris Fermented with Pediococcus pentosaceus SC11 Isolated from a Salted Small Octopus in Cyclophosphamide-Induced Immunocompromised Mice and Its Inhibitory Activity against SARS-CoV 3CL Protease

In this study, we investigated the immune-enhancing and anti-viral effects of germinated Rhynchosia nulubilis (GRC) fermented with Pediococcus pentosaceus SC11 (GRC-SC11) isolated from a salted small octopus. The cordycepin, β-glucan, and total flavonoid contents increased in GRC after SC11 fermentation. GRC-SC11 inhibits 3CL protease activity in severe acute respiratory syndrome-associated coronavirus (SARS-CoV). GRC-SC11 significantly increased thymus and spleen indices in immunocompromised mice. The rate of splenocyte proliferation was higher in GRC-SC11-treated immunocompromised mice than that in GRC-treated immunocompromised mice in the presence or absence of concanavalin A. In addition, GRC-SC11 increased the phagocytic activity and nitric oxide production in immunocompromised mice. The mRNA expression of interferon-gamma (IFN-γ), interferon-alpha (IFN-α), and interferon-stimulated gene 15 (ISG15) was up-regulated in GRC-SC11 treated RAW 264.7 macrophages, compared to GRC. Our study indicates that GRC-SC11 might be a potential therapeutic agent for immunocompromised patients who are vulnerable to SARS-CoV infection.

New Insights Into the Biosynthesis of Typical Bioactive Components in the Traditional Chinese Medicinal Fungus Cordyceps militaris

Cordyceps militaris, a traditional medicinal ingredient with a long history of application in China, is regarded as a high-value fungus due to its production of various bioactive ingredients with a wide range of pharmacological effects in clinical treatment. Several typical bioactive ingredients, such as cordycepin, D-mannitol, cordyceps polysaccharides, and N⁶-(2-hydroxyethyl)-adenosine (HEA), have received increasing attention due to their antitumor, antioxidant, antidiabetic, radioprotective, antiviral and immunomodulatory activities. Here, we systematically sorted out the latest research progress on the chemical characteristics, biosynthetic gene clusters and pathways of these four typical bioactive ingredients. This summary will lay a foundation for obtaining low-cost and high-quality bioactive ingredients in large amounts using microbial cell factories in the future.

Therapeutic Potential and Biological Applications of Cordycepin and Metabolic Mechanisms in Cordycepin-Producing Fungi

Cordycepin (3′-deoxyadenosine), a cytotoxic nucleoside analogue found in Cordyceps militaris, has attracted much attention due to its therapeutic potential and biological value. Cordycepin interacts with multiple medicinal targets associated with cancer, tumor, inflammation, oxidant, polyadenylation of mRNA, etc. The investigation of the medicinal drug actions supports the discovery of novel targets and the development of new drugs to enhance the therapeutic potency and reduce toxicity. Cordycepin may be of great value owing to its medicinal potential as an external drug, such as in cosmeceutical, traumatic, antalgic and muscle strain applications. In addition, the biological application of cordycepin, for example, as a ligand, has been used to uncover molecular structures. Notably, studies that investigated the metabolic mechanisms of cordycepin-producing fungi have yielded significant information related to the biosynthesis of high levels of cordycepin. Here, we summarized the medicinal targets, biological applications, cytotoxicity, delivery carriers, stability, and pros/cons of cordycepin in clinical applications, as well as described the metabolic mechanisms of cordycepin in cordycepin-producing fungi. We posit that new approaches, including single-cell analysis, have the potential to enhance medicinal potency and unravel all facets of metabolic mechanisms of cordycepin in Cordyceps militaris.