Endophytic fungi from the medicinal herb Euphorbia geniculata as a potential source for bioactive metabolites

Applications of endophytic fungi in plant disease control

Diseases caused by pathogenic microorganisms (bacteria, fungi, and viruses) have resulted in the quality and yield of crops, which has seriously affected the development of the agricultural economy. The prolonged use of chemical fungicides for prevention and control can lead to environmental pollution, hindering the sustainable development of safe and eco-friendly agriculture while also promoting the resistance of pathogenic microorganisms. Nevertheless, non-pathogenic endophytic fungi that form symbiotic relationships with plants still exhibit significant antagonistic effects on pathogenic microorganisms, even in small concentrations. These fungi pose no threat to human health and are highly beneficial to the ecological environment, making them an ideal alternative to chemical fungicides. They are increasingly being recognized and have been subjected to comprehensive research. Based on this, this article summarizes the types of endophytic fungi with biocontrol effects in recent years. It focuses on elucidating the mechanisms of their biocontrol from physiological and molecular perspectives. In addition, the application and development challenges of biocontrol agents (BCAs) derived from these fungi are also discussed, including difficulties in elucidating their mechanisms of action during research and development, challenges in strain selection and improvement, difficulties in controlling environmental adaptability, and stringent storage conditions. The aim is to develop more effective endophytic fungi as emerging biocontrol resources for agricultural production.

Two Novel Plant-Growth-Promoting Lelliottia amnigena Isolates from Euphorbia prostrata Aiton Enhance the Overall Productivity of Wheat and Tomato

Euphorbiaceae is a highly diverse family of plants ranging from trees to ground-dwelling minute plants. Many of these have multi-faceted attributes like ornamental, medicinal, industrial, and food-relevant values. In addition, they have been regarded as keystone resources for investigating plant-specific resilience mechanisms that grant them the dexterity to withstand harsh climates. In the present study, we isolated two co-culturable bacterial endophytes, EP1-AS and EP1-BM, from the stem internodal segments of the prostate spurge, Euphorbia prostrata, a plant member of the succulent family Euphorbiaceae. We characterized them using morphological, biochemical, and molecular techniques which revealed them as novel strains of Enterobacteriaceae, Lelliotia amnigena. Both the isolates significantly were qualified during the assaying of their plant growth promotion potentials. BM formed fast-growing swarms while AS showed growth as rounded colonies over nutrient agar. We validated the PGP effects of AS and BM isolates through in vitro and ex vitro seed-priming treatments with wheat and tomato, both of which resulted in significantly enhanced seed germination and morphometric and physiological plant growth profiles. In extended field trials, both AS and BM could remarkably also exhibit productive yields in wheat grain and tomato fruit harvests. This is probably the first-ever study in the context of PGPB endophytes in Euphorbia prostrata. We discuss our results in the context of promising agribiotechnology translations of the endophyte community associated with the otherwise neglected ground-dwelling spurges of Euphorbiaceae.

Endophytic fungi mediates production of bioactive secondary metabolites via modulation of genes involved in key metabolic pathways and their contribution in different biotechnological sector

Endophytic fungi stimulate the production of an enormous number of bioactive metabolites in medicinal plants and affect the different steps of biosynthetic pathways of these secondary metabolites. Endophytic fungi possess a number of biosynthetic gene clusters that possess genes for various enzymes, transcription factors, etc., in their genome responsible for the production of secondary metabolites. Additionally, endophytic fungi also modulate the expression of various genes responsible for the synthesis of key enzymes involved in metabolic pathways of such as HMGR, DXR, etc. involved in the production of a large number of phenolic compounds as well as regulate the expression of genes involved in the production of alkaloids and terpenoids in different plants. This review aims to provide a comprehensive overview of gene expression related to endophytes and their impact on metabolic pathways. Additionally, this review will emphasize the studies done to isolate these secondary metabolites from endophytic fungi in large quantities and assess their bioactivity. Due to ease in synthesis of secondary metabolites and their huge application in the medical industry, these bioactive metabolites are now being extracted from strains of these endophytic fungi commercially. Apart from their application in the pharmaceutical industry, most of these metabolites extracted from endophytic fungi also possess plant growth-promoting ability, bioremediation potential, novel bio control agents, sources of anti-oxidants, etc. The review will comprehensively shed a light on the biotechnological application of these fungal metabolites at the industrial level.

Diversity of Culturable Endophytic Fungi in Crocus sativus and Their Correlation with Crocin Content

The presence and diversity of endophytic fungi associated with host plants are important not just for host plant growth and defense, but also impact the production of medicinal secondary metabolites. However, the correlation between endophytic fungi and crocin production in Crocus sativus (CS) remains underexplored. Here, we explore the relationship between endophytic fungal diversity and crocin content among different CS tissues and field sites. Specifically, we isolated endophytic fungi from five different field sites (Shanghai, Jiande, Huzhou, Anhui, and Hebei) and five different tissues (corm, scape, leaf, petal, and stigma) and analyzed fungal community diversity, richness, and evenness. We identified a total of 32 endophytic fungal taxa, assigned to 7 orders within 4 classes (Eurotiomycetes, Agaricomycetes, Dothideomycetes, and Sordariomycetes). The most dominant order was Eurotiales, and the most dominant genera were Penicillium and Talaromyces. Species richness tended to be highest in belowgrown tissues, such as corm and scape. Additionally, several fungal taxa were found to be either site- or tissue-specific. Three genera in particular were correlated with crocin content: Penicillium, Sistotrema, and Bjerkandera. Given the fact that endophytic microorganisms can both promote the production of secondary metabolites in host plants and potentially produce secondary metabolites themselves, further study is required to understand the mechanistic relationship between these and other fungal genera and crocin production.

Metabolites of medicine food homology-derived endophytic fungi and their activities

Medicine food homology (MFH) substances not only provide essential nutrients as food but also have corresponding factors that can prevent and help treat nutritional imbalances, chronic disease, and other related issues. Endophytic fungi associated with plants have potential for use in drug discovery and food therapy. However, the endophytic fungal metabolites from MFH plants and their effects have been overlooked. Therefore, this review focuses on the various biological activities of 108 new metabolites isolated from 53 MFH-derived endophytic fungi. The paper explores the potential nutritional and medicinal value of metabolites of MFH-derived endophytic fungi for food and medical applications. This research is important for the future development of effective, safe, and nontoxic therapeutic nutraceuticals for the prevention and treatment of human diseases.

Identification of Macrolepiota procera extract as a novel G6PD inhibitor for the treatment of lung cancer

Tumor metabolism, an emerging hallmark of cancer, is characterized by aberrant expression of enzymes from various metabolic pathways including glycolysis and PPP (pentose phosphate pathway). Glucose 6 phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), oxidative carboxylases of PPP, have been reported to accomplish different biosynthetic and energy requirements of cancer cells. G6PD and 6PGD have been proposed as potential therapeutic targets for cancer therapy during recent years due to their overexpression in various cancers. Here, we have employed enzymatic assay based screening using in-house G6PD and 6PGD assay protocols for the identification of mushroom extracts which could inhibit G6PD or 6PGD enzymatic activity for implications in cancer therapy. For the fulfillment of the objectives of present study, nine edible mushrooms were subjected to green extraction for preparation of ethanolic extracts. 6xhis-G6PD and pET-28a-h6PGD plasmids were expressed in BL21-DE3 E. coli cells for the expression and purification of protein of interests. Using purified proteins, in house enzymatic assay protocols were established. The preliminary screening identified two extracts (Macrolepiota procera and Terfezia boudieri) as potent and selective G6PD inhibitors, while no extract was found highly active against 6PGD. Further, evaluation of anticancer potential of mushroom extracts against lung cancer cells revealed Macrolepiota procera as potential inhibitor of cancer cell proliferation with IC50 value of 6.18 μg/ml. Finally, screening of M. procera-derived compounds against G6PD via molecular docking has identified paraben, quercetin and syringic acid as virtual hit compounds possessing good binding affinity with G6PD. The result of present study provides novel findings for possible mechanism of action of M. procera extract against A549 via G6PD inhibition suggesting that M. procera might be of therapeutic interest for lung cancer treatment.

Comparative Studies on the Antioxidant, Antifungal, and Wound Healing Activities of Solenostemma arghel Ethyl Acetate and Methanolic Extracts

Various herbal compounds are used for medical purposes due to their safety, as there are no or minimal side effects. This study was performed to assess the wound healing and antioxidant activities of ethyl acetate (EtOAc) and methanolic extract (MeoH) of Solenostemma arghel (S. arghel). Their antifungal activities were also evaluated against isolated swabs of equine wounds. They underwent GC-MS analysis for the characterization of both extracts. For wound healing evaluation, forty-five male albino rats were divided into three groups; the control group was treated with normal saline, and the other two groups were treated with S. arghel EtOAc and MeoH extract gels, respectively. The wounds were examined clinicopathologically and immunohistochemistry on the 3rd, 7th, and 14th days post-wounding. GC-Ms analysis of S. arghel recorded fifty-one volatile organic compounds (VOCs) within EtOAc extraction and thirty VOCs in MeoH extract. VOCs represented in EtOAc extract showed higher antioxidant activity and better and faster wound healing than VOCs of MeOH extract. The treated groups showed improved wound healing clinically and pathologically in comparison with the control group as they decreased the wound surface area (WSA) and percent (WSA%) and increased the wound contraction percent (WC%), epithelization, fibroblast proliferation with neovascularization, and reduced the inflammatory reaction. Moreover, the treated groups showed higher expression of vascular endothelial growth factor (VEGF) compared with the control. The EtOAc extract showed higher antifungal activity against Penicillium funiculosum, P. jensenii, M. cinctum, and Candida albicans, which were isolated from infected clinical equine wounds, than MeOH extract. The treated groups showed improved wound healing clinically and pathologically in comparison with the control group as they decreased the wound surface area (WSA) and percent (WSA%) and increased the wound contraction percent (WC%), epithelization, fibroblast proliferation with neovascularization, and reduced the inflammatory reaction. Moreover, the treated groups showed higher expression of vascular endothelial growth factor (VEGF) compared with the control. Additionally, the two extract gels showed promising healing of equine wounds. In conclusion, the study recommended the use of S. arghel EtOAc extract as it was proven to promote wound healing compared with MeoH extract.

Screening saikosaponin d (SSd)-producing endophytic fungi from Bupleurum scorzonerifolium Willd

Saikosaponin d (SSd) is an important bioactive compound of traditional Chinese medicinal plant Bupleurum scorzonerifolium Willd. and exhibits many effects, such as anti-tumor, anti-inflammation and immunomodulatory. Since endophytic fungi possess the natural capacity to produce the similar secondary metabolite to that of their host plants, they are promising as alternative sources of plant bioactive natural products. In this study, in order to search for SSd-producing strains, endophytes were isolated from B. scorzonerifolium and were authenticated by the ITS sequence and the translation elongation factor-1alpha gene (TEF-1α) sequence analysis. The profile of metabolites present in the crude exacts was carried out by ultra performance liquid chromatography time-of-flight mass spectrometry (UPLC/Q-TOF-MS) analysis. The results showed that two strains, CHS₂ and CHS₃ from B. scorzonerifolium could produce SSd by UPLC/Q-TOF-MS analysis, and the amount of SSd produced by strain CHS₂ and CHS₃ were about 2.17 and 2.40 µg/mL, respectively. CHS₂ and CHS₃ showed a close phylogenetic relationship to Fusarium oxysporum and Fusarium acuminatum, respectively. According to our concern, no endophytic fungi capable of producing SSd from B. scorzonerifolium have been found before. Our clear intention was to isolate and identify these endophytic fungi that produce important active secondary metabolites, and then study the strains that produce this compound on a large scale through fermentation or even genetic study, to provide a feasible and more convenient way for the production of SSd.

Endophytic fungi inhabiting Physalis angulata L. plant: diversity, antioxidant, and antibacterial activities of their ethyl acetate extracts

OBJECTIVES

Endophytic fungi are an essential source of biologically active compounds. They have the ability to synthesize secondary metabolites which are the same or have a high degree of similarity to their host plants. In this study, we aimed to explore the biodiversity and the bioactivities of active metabolites produced by 14 endophytic fungi isolated from the medicinal plant Physalis angulata L. (PA).

METHODS

Fourteen endophytic fungi were isolated from the flowers, stems, leaves, and fruit husks of PA. The endophytic fungi were cultured and incubated in the PDB medium at room temperature. After three weeks, the cultures were extracted using ethyl acetate and dried using a rotary evaporator. The antioxidant activity was evaluated against DPPH while antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus using microdilution technique. TLC analysis was also done to profile the active compounds within the extract.

RESULTS

Hyphomycetes fungus isolated from the flower of PA exhibited a moderate antioxidant activity with an antioxidant index value of 0.59 (IC₅₀ = 52.43 μg/mL). Six isolates have strong antibacterial activity against E. coli and S. aureus with minimum inhibitory concentration (MIC) value ranging from 8-64 μg/mL. These endophytic fungi are one Hyphomycetes fungus isolated from the flower, one Fusarium sp. isolated from the stem, and four Colletotrichum sp. isolated from leaf and fruit husk of PA.

CONCLUSIONS

Endophytic fungi isolated from PA are potential novel sources of active metabolites especially for antibacterial compounds.

Geographical Isolation and Root-Associated Fungi in the Marine Terrains: A Step Toward Establishing a Strategy for Acquiring Unique Microbial Resources

This study aimed to understand whether the geo-ecological segregation of native plant species affects the root-associated fungal community. Rhizoplane (RP) and rhizosphere (RS) fungal microbiota of Sedum takesimense native to three geographically segregated coastal regions (volcanic ocean islands) were analyzed using culture-independent methods: 568,507 quality sequences, 1399 operational taxonomic units, five phyla, and 181 genera were obtained. Across all regions, significant differences in the phyla distribution and ratio were confirmed. The Chao's richness value was greater for RS than for RP, and this variance coincided with the number of genera. In contrast, the dominance of specific genera in the RS (Simpson value) was lower than the RP at all sites. The taxonomic identity of most fungal species (95%) closely interacting with the common host plant was different. Meanwhile, a considerable number of RP only residing fungal genera were thought to have close interdependency on their host halophyte. Among these, Metarhizium was the sole genus common to all sites. These suggest that the relationship between potential symbiotic fungi and their host halophyte species evolved with a regional dependency, in the same halophyte species, and of the same natural habitat (volcanic islands); further, the fungal community differenced in distinct geographical regions. Importantly, geographical segregation should be accounted for in national culture collections, based on taxonomical uniqueness.

Bioactive Metabolites from the Endophytic Fungus Aspergillus sp. SPH2

In the current study, an ethyl acetate extract from the endophytic fungus Aspergillus sp. SPH2 isolated from the stem parts of the endemic plant Bethencourtia palmensis was screened for its biocontrol properties against plant pathogens (Fusarium moniliforme, Alternaria alternata, and Botrytis cinerea), insect pests (Spodoptera littoralis, Myzus persicae, Rhopalosiphum padi), plant parasites (Meloidogyne javanica), and ticks (Hyalomma lusitanicum). SPH2 gave extracts with strong fungicidal and ixodicidal effects at different fermentation times. The bioguided isolation of these extracts gave compounds 1-3. Mellein (1) showed strong ixodicidal effects and was also fungicidal. This is the first report on the ixodicidal effects of 1. Neoaspergillic acid (2) showed potent antifungal effects. Compound 2 appeared during the exponential phase of the fungal growth while neohydroxyaspergillic acid (3) appeared during the stationary phase, suggesting that 2 is the biosynthetic precursor of 3. The mycotoxin ochratoxin A was not detected under the fermentation conditions used in this work. Therefore, SPH2 could be a potential biotechnological tool for the production of ixodicidal extracts rich in mellein.

Bio-Guided Fractionation of Prenylated Benzaldehyde Derivatives as Potent Antimicrobial and Antibiofilm from Ammi majus L. Fruits-Associated Aspergillus amstelodami

Ammi majus L.; Family Apiaceae; is a plant indigenous to Egypt. Its fruits contain bioactive compounds such as furanocoumarins and flavonoids of important biological activities. An endophytic fungus was isolated from the fruits and identified as Aspergillus amstelodami (MK215708) by morphology, microscopical characterization, and molecular identification. To our knowledge this is the first time an endophytic fungus has been isolated from the fruits. The antimicrobial activity of the Ammi majus ethanol fruits extract (AME) and fungal ethyl acetate extract (FEA) were investigated, where the FEA showed higher antimicrobial activity, against all the tested standard strains. Phytochemical investigation of the FEA extract yielded five prenylated benzaldehyde derivative compounds isolated for the first time from this species: Dihydroauroglaucin (1), tetrahydroauroglaucin (2), 2-(3,6-dihydroxyhepta-1,4-dien-1-yl)-3,6-dihydroxy-5-(dimethylallyl)benzaldehyde (3), isotetrahydroauroglaucin )4), and flavoglaucin (5). Structure elucidation was carried out using (1H- and 13C-NMR). Fractions and the major isolated compound 1 were evaluated for their antimicrobial and antibiofilm activity. Compound 1 showed high antimicrobial activity against Escherichia coli with minimum inhibitory concentration (MIC) = 1.95 µg/mL, Streptococcus mutans (MIC = 1.95 µg/mL), and Staphylococcus aureus (MIC = 3.9 µg/mL). It exhibited high antibiofilm activity with minimum biofilm inhibitory concentration (MBIC) = 7.81 µg/mL against Staphylococcus aureus and Escherichia coli biofilms and MBIC = 15.63 µg/mL against Streptococcus mutans and Candida albicans and moderate activity (MBIC = 31.25 µg/mL) against Pseudomonas aeruginosa biofilm. This reveals that dihydroauroglaucin, a prenylated benzaldehyde derivative, has a broad spectrum antimicrobial activity. In conclusion, it was observed that the MICs of the FEA are much lower than that of the AME against all susceptible strains, confirming that the antimicrobial activity of Ammi majus may be due to the ability of its endophytic fungi to produce effective secondary metabolites.