Endophytic fungi are ubiquitous in the health tissues and organs of medicinal plants, with a great number of species and a wide range of distribution. To date, a large number of species have been isolated from diverse medicinal plants distributed in various ecological environments in the world, except Antarctica. With the rapid development of modern science and technology, the research on endophytic fungi in medicinal plants has achieved remarkable progress. In this paper, research progress on endophytic fungi in medicinal plant is summarized, and the future development trend in this field is expected and predicted.
A special symbiotic relationship perpetually exists between endophytic fungi and host medicinal plants. Endophytic fungi have an important effect on growth, productivity, quality, bioactive compounds and adversity resistance of medicinal plants. Some physiologically active compounds produced by endophytic fungi of medicinal plants have shown a huge potential in new drug research and development, medicinal plant cultivation, fungal fertilizer development, biological control agent development, contaminated soil bioremediation and industrialized production of enzyme. The richness of medicinal plants in China must be endowed with a large number of unknown endophytic fungi. This resource treasure need to be explored and developed urgently.
Orchid seeds are tiny, without endosperm and must depend on suitable endophytic fungi to germinate under natural conditions. More and more studies have shown that endophytic fungi can provide the necessary carbon nutrients, nitrogen and other nutrient sources for the seed germination of medicinal plants of Orchidaceae. The research progress concerning nutrients provided by endophytic fungi for seeds of orchid medicinal plants are reviewed, and the nutritional relationships between endophytic fungi and orchid seed germination are discussed.
Gymnadenia conopsea is a terrestrial orchid, a kind of traditional Chinese herbal medicine. Based on Illumina MiSeq high-throughput sequencing technology targeting ITS1 region, endophytic fungal communities associated with G. conopsea growing in Beijing were analyzed. A total of 50 420 effective sequences were selected and classified into 209 operational taxonomic units (OTUs), belonging to 54 families, 28 orders, 9 classes, and 3 phyla. Nine classes correspond to Pezizomycetes (3 OTUs), Agaricomycetes (21 OTUs), Leotiomycetes (18 OTUs), Sordariomycetes (51 OTUs), Zygomycetes (18 OTUs), Tremellomycetes (19 OTUs), Eurotiomycetes (22 OTUs), Saccharomycetes (8 OTUs), and Dothideomycetes (14 OTUs). The endophytic fungi belonging to Cantharellales (38.62%) and Helotiales (24.64%) were found to be dominant in the roots of G. conopsea from Baihua Mountain, and species of Pezizales (66.19%) and Cantharellales (29.75%) were dominant in Song Mountain. These results laid a foundation for understanding the endophytic fungal community composition of G. conopsea in Beijing and applying endophytic fungi to artificial breeding of the orchid.
The endophytic fungi in different tissues of Nothapodytes pittosporoides in different seasons from Guizhou Province were investigated and evaluated. Based on phylogenetic method, 1 037 strains of endophytic fungi from 1 444 samples of N. pittosporoides tissues collected from three counties were obtained, belonging to 30 genera, of which Diaporthe was dominant, and the isolation rate and frequency were 40.24% and 57.58% respectively. Diversity index was the highest in summer, and the similarity index for four seasons was 0.40-0.71, being the highest in Xiuwen, Guiyang. The similarity index of the fungi in three counties was 0.42-0.55. The diversity index of the fungi in fruit was the highest, and the similarity index for each sample tissues was 0.00-0.54.
In nature, orchid seeds possess no endosperm and therefore are devoid of nutrient supply. Mycorrhizal fungi (e.g., Mycena dendrobii) can provide the orchid seeds with signals and nutrients for germination. The mature seeds and protocorms of Gastrodia elata, and the hyphae of M. dendrobii were sequenced by using RNA-seq platform to elucidate the changes of gene expression in G. elata. All unigenes were searched against seven public databases and 42 263 unigenes were annotated in at least one database. We analyzed 5 409 differentially expressed unigenes through clustering and functional enrichment. Based on GO analysis, most genes were classified as the functors involving metabolism, signal transduction, and binding. KEGG analysis results indicated that the differentially expressed genes participated in translation, carbohydrate metabolism, signal transduction, plant hormone signal transduction, carbon metabolism, phenylpropanoid biosynthesis, starch and sucrose metabolism, and phenylalanine metabolism. The hydrolase genes that act on the cell walls of fungi or plants, such as chitinase, β-glucanase, xylanase and pectinase, showed higher expression in protocorms than in mature seeds. The oligosaccharide elicitors were released from cell walls. Our results indicated that the accumulation of elicitors may play important roles in the defense mechanism when the seeds infected by symbiotic fungi.
Gastrodia elata, a well-known medicinal herb, is a typical mycoheterotrophic orchid. To germinate successfully, it is crucial for G. elata to obtain nutrients from mycorrhizal fungi such as Mycena. To date, molecular interactions between this orchid and fungi remain the hot research area. Here we used the proteomic approach to explore the proteome changes during the seed germination of G. elata. An iTRAQ-labelled LC-MS technique was employed for proteomics analysis, and a total of 1 769 unique proteins were identified (global FDR 1%), of which 269 were classified as differentially accumulated proteins. GO analysis indicated that most of these differentially expressed proteins were putatively involved in binding, catalytic activity, response to stimulus, molecular signaling and transduction. KEGG analysis revealed that most of them were associated with signal transduction, energy metabolism, secondary metabolism, environmental adaptation and so on. Among them, numerous proteins involved in endocytosis were identified from our data, suggesting that endocytosis could play important roles in symbiotic seed germination of G. elata with Mycena infections. It is the first study of the proteome of G. elata, which may be useful to advance the knowledge on fungus-symbiotic plant seed germination.
This study aims at optimizing DNA extraction methods of endophytic Xylaria from Dendrobium and authenticating the fungus based on ITS and secondary structures of ITS2. Extraction effects of kit method and CTAB method at different concentration (2%, 3%, 4%) were compared and CTAB method was optimized. ITS sequence was amplified and the secondary structure of ITS2 was predicted. Results indicated that the best extraction effect was derived from CTAB at concentration of 4% and the optimized CTAB method was greatly reduced DNA extraction duration. The ITS sequence of experimental Xylaria strain TJ1 showed 99% similarity to that of three species of Xylaria, X. arbuscula, X. apiculata and X. venosula, while the secondary structure of ITS2 of the strain showed 100% similarity to that of Xylaria arbuscula. The optimized CTAB method will provide convenience of future research and the endophytic Xylaria of Dendrobium can be identified accurately based on combining ITS sequence with secondary structures of ITS2.
A escin C high-yielding endophytic fungus isolated from Aesculus chinensis tissue collected from Liuba, Shaanxi Province is numbered as EA-LJS80. Using ITS sequence analysis the fungus was identified as Aspergillus sp. The maximum UV absorption peak was determined by using UV-VIS spectrophotometer full wavelength scan. The yield of escin C was determined by using HPLC. Filter paper diffusion method was used for testing the antibacterial activity of fermentation broth extract. Using CCK-8 method, inhibition rate of A549 cell after treating with the extract was determined to explore bioactivities of the extract. The maximum UV absorption wavelength of Aspergillus sp. EA-LJS80 extract was 230nm. The yield of escin C was 9.23mg/mL after purification of the fermentation extract. Bioactivity tests showed that the extract had significantly inhibitory effect on Escherichia coli and other four kinds of pathogenic bacteria. The extract also had significantly inhibitory effect on A549 cells as was determinated by CCK-8 method. This study provides important reference data for promoting further study of escin C.
Three phenolic acid analogs, barceloneic acid A (1), barceloneic lactone (2), and 2′-O-methyl-barceloneate (3), were isolated from the endophytic fungus Embellisia chlamydospora collected from desert medicinal plant Artemisia desertorum. The structures of these compounds were elucidated on the basis of NMR and HR-ESI data. All elopathic test showed that compounds 2 and 3 significantly retarded root growth of Arabidopsis thaliana. Up to date, there are only two compounds (terpestacin and embellistatin) isolated from this fungus. This study implies that fungi inhabiting in unique environments are a huge and potential treasure of novel and bioactive secondary metabolites.
Cladosporium sp. SM58, endophytic fungi in medicinal plant Salvia miltiorrhiza is beneficial for growth promotion and improvement of salvianolic acid content of S. miltiorrhiza. The tissue-cultured seedlings or seedlings of S. miltiorrhiza were inoculated with solid-medium-cultured Cladosporium sp. SM58 and then were cultivated under conditions of tissue culture, pot culture and field cultivation. The effect of this fungus on the growth of seedlings was observed. The effects of the fungus on the content of effective component of salvianolic acid and biomass of S. miltiorrhiza seedlings were also surveyed after six months. The microstructure changes of the root of S. miltiorrhiza under field culture were observed under light microscope and scanning electron microscope. The results showed that Cladosporium sp. SM58 not only promoted the growth of tissue-cultured seedlings, increased the growth of root and improved the plant biomass (P<0.01), but also significantly affected the growth of S. miltiorrhiza under pot and field culture, and increased the content of effective component of salvianolic acid and plant biomass (P<0.01). The biomass of the inoculated S. miltiorrhiza under field culture was 68.4% higher than that of the plants in control group. Compared with the control group, the content of total phenolic acid and salvianolic acid A was increased respectively by 47.3% and 11.1%. Observation under light microscope revealed that the hypha of SM58 infected the epidermic and cortical cells of S. miltiorrhiza root. This study indicated that the strain SM58 has a beneficial effect on the quality and yield of S. miltiorrhiza.
An endophytic fungus strain JR14 with acetylcholinesterase (AChE) inhibitory activity from Huperzia serrata was identified as Pezicula sp. by morphological characteristics and internal transcribed spacer (ITS) sequence analysis. Four kinds of secondary metabolites were separated and purified from the ethyl acetate extract of the endophytic Pezicula sp. JR14. According to mass spectrometry, 1H-NMR and 13C-NMR analyses, they were identified as behenic acid (1), himeic acid B (2), secalonic acid A (3) and palmitic acid (4). Ellman colorimetric test proved that himeic acid B (2) showed better AChE inhibitory activity with IC50 value of 205μg/mL (0.64mmol/L).
Diverse medicinal plants in Tianshan mountainous area of Xinjiang conceal unique and abundant endophytic fungi, especially dark septate endophytes (DSE), which play an important role in environmental adaptation during the growth and development of the medicinal plants. The species diversity of endophytic fungi colonized in medicinal plants of Tianshan is imperfectly known. In this study, the culturable and unculturable endophytic fungi from the root of the medicinal plants Saussurea involucrata and Rhodiola rosea were preliminarily investigated and 34 strains were isolated. There were 4/5 of the isolates being identified as DSE based on morphological characters. A total of 143 fungal clones were obtained and more than 1/3 of the clones were identified as members of Helotiales and Pleosporales. A phylogenetic analysis revealed these fungi closely related to Cadophora, Leptodontidium, Phialocephala and Phialophora, which are well-known DSE frequently isolated from various plants. The results showed that DSE were extremely abundant in the roots of S. involucrata and R. rosea, indicating that they might be involved in the ecological adaptation of plants to resist cold and strong radiation.
One compound was obtained by natural precipitation from the metabolite of an endophytic fungus Penicillium sp. isolated from Taxus chinensis var. mairei, and it was identified as penitrem A by chromatogram and literature comparison. MTT assay showed the compound had antitumor effect on malignant melanoma cell A375, the inhibition increased with the increase of concentration, and its IC50 value was 27.24μg/mL. This is the first time to obtain penitrem A from the metabolite of endophytic fungi isolated from Taxus, and provides a theoretical reference for the development of antitumor drugs.
