Ethylidene-Tethered Chromene-Pyrone Hybrids as Potential Plant-Growth Regulators from an Endolichenic Phaeosphaeria Species

Comparative Antagonistic Activities of Endolichenic Fungi Isolated from the Fruticose Lichens Ramalina and Usnea

Persistent fungal pathogens remain a threat to global food security as these pathogens continue to infect crops despite different mitigating strategies. Traditionally, synthetic fungicides are used to combat these threats, but their environmental and health impacts have spurred interest in a more sustainable, eco-friendly approach. Endolichenic fungi (ELF) are a relatively underexplored group of microorganisms found thriving inside the lichen thalli. They are seen as promising alternatives for developing sustainable plant disease management strategies. Hence, in this study, a total of forty ELF isolates from two fruticose lichen hosts-Ramalina and Usnea, were tested and compared for their antagonistic activities against three economically important filamentous fungal pathogens-Colletotrichum gloeosporioides, Cladosporium cladosporioides, and Fusarium oxysporum. The results of the dual culture assay showed that all ELF isolates successfully reduced the growth of the three filamentous fungal pathogens with varying degrees, and with direct contact inhibition as the predominant trait among the endolichenic fungi. Comparing the antagonistic activities between the different endolichenic fungi from the two lichen hosts, ELF isolates from Ramalina generally demonstrated a higher percentage inhibition of growth of the test fungi as compared to ELF isolates from Usnea. This study underscores the importance of endolichenic fungi as an efficient biocontrol agent.

Fungal Coculture of Herpotrichia sp. and Trametes versicolor Induces Production of Diverse Metabolites with Anti-Parkinson's Neuroprotective Activity

Co-cultivation of isopod-associated fungi Herpotrichia sp. SF09 and Trametes versicolor SF09A led to the reciprocal induction of thirteen new compounds (1-7 and 9-13) with diverse architectures. Importantly, compounds 1 and 2 are rare fungal sesquiterpene-saccharide hybrids incorporating a xylopyranose moiety, compound (±)-3 represents the first example of a natural linear sesquiterpene racemate, and compound 7 is a rare α-pyrone derivative with a xylopyranose motif. Their structures were elucidated by analysis of NMR and mass spectrometry data, and their absolute configurations were determined by Mosher's method, microscale derivatization, and single-crystal X-ray diffraction, as well as ECD calculations. All the isolated compounds ameliorated MPP+-induced oxidative damage in PC12 cells in a dose-dependent fashion. Among them, compounds 5 and 15 showed significant protective action against neuronal injury by MPP+ at 5 μM. Meanwhile, transcriptome sequencing was performed to evaluate the molecular mechanism of the neuroprotective activity for compound 5. Results indicated that compound 5 might mitigate MPP+-induced neuronal injury through the regulation of multiple signaling pathways, including the PI3K-Akt and MAPK pathways. Our findings suggested that compound 5 could be a promising neuroprotective agent for the treatment of Parkinson's disease.

New bioactive secondary metabolites from fungi: 2023

Fungi have been identified as a prolific source of structurally unique secondary metabolites, many of which display promising biological and pharmacological properties. This review provides an overview of the structures of new natural products derived from fungi and their biological activities along with the research strategies, which focuses on literature published in the representative journals in 2023. In this review, a total of 553 natural products including 219 polyketides, 145 terpenoids, 35 steroids, 106 alkaloids, and 48 peptides are presented. By summarising the latest findings, this review aims to provide a guide and inspire further innovation in the fields of the discovery of fungal natural products and pharmaceutical development.

Polyketides with α-glucosidase inhibitory and neuroprotective activities from Aspergillus versicolor associated with Pedicularis sylvatica

Aspergillus versicolor, an endophytic fungus associated with the herbal medicine Pedicularis sylvatica, produced four new polyketides, aspeversins A-D (1-2 and 5-6) and four known compounds, O-methylaverufin (2), aversin (3), varilactone A (7) and spirosorbicillinol A (8). Their structures were elucidated by extensive spectroscopic data analysis, and their absolute configurations were determined by calculated electronic circular dichroism (ECD) and Mo2(AcO)4-induced CD data. Compound 5 was found to exhibit α-glucosidase inhibitory activity with an IC50 value of 25.57 μM. An enzyme kinetic study indicated that 5 was a typical uncompetitive inhibitor toward α-glucosidase, which was supported by a molecular docking study. Moreover, compounds 1-3 and 5 also improved the cell viability of PC12 cells on a 1-methyl-4-phenylpyridinium (MPP+)-induced Parkinson's disease model, indicating their neuroprotective potential as antiparkinsonian agents.

Succession of tissue microbial community during oat developmental

Investigating oat tissue microflora during its different developmental stages is necessary for understanding its growth and anti-disease mechanism. In this study, 16S rDNA and ITS (Internally Transcribed Spacer) high-throughput sequencing technology were used to explore the microflora diversity of oat tissue. Twenty-seven samples of leaves, stems, and roots from three developmental stages, namely the seedling stage (SS), jointing stage (JS), and maturity stage (MS), underwent sequencing analysis. The analysis showed that 6480 operational taxonomic units (OTUs) were identified in the examined samples, of which 1698 were fungal and 4782 were bacterial. Furthermore, 126 OTUs were shared by fungi, mainly Ascomycota, Basidiomycota, and Mucoromycota at the phylum level, and 39 OTUs were shared by bacteria, mainly Actinobacteriota and Proteobacteria at the phylum level. The microbial diversity of oat tissue in the three developmental stages showed differences, and the α-diversity of the bacteria and β-diversity of the bacteria and fungi in the roots were higher than those of the stems and leaves. Among the bacteria species, Thiiopseudomonas, Rikenellaceae RC9 gut group, and Brevibacterium were predominant in the leaves, MND1 was predominant in the roots, and Lactobacillus was predominant in the stems. Moreover, Brevibacterium maintained a stable state at all growth stages. In the fungal species, Phomatospora was dominant in the leaves, Kondoa was dominant in the roots, and Pyrenophora was dominant in the stems. All species with a high abundance were related to the growth process of oats and antagonistic bacteria. Furthermore, connection modules were denser in bacterial than in fungal populations. The samples were treated with superoxide dismutase and peroxidase. There were 42 strains associated with SOD (Superoxide dismutase), 60 strains associated with POD (Peroxidase), and 38 strains in total, which much higher than fungi. The network analysis showed that bacteria might have more dense connection modules than fungi, The number of bacterial connections to enzymes were much higher than that of fungi. Furthermore, these results provide a basis for further mechanistic research.

Endolichenic Fungi: A Promising Medicinal Microbial Resource to Discover Bioactive Natural Molecules-An Update

Lichens are some of the most unique fungi and are naturally encountered as symbiotic biological organisms that usually consist of fungal partners (mycobionts) and photosynthetic organisms (green algae and cyanobacteria). Due to their distinctive growth environments, including hot deserts, rocky coasts, Arctic tundra, toxic slag piles, etc., they produce a variety of biologically meaningful and structurally novel secondary metabolites to resist external environmental stresses. The endofungi that live in and coevolve with lichens can also generate abundant secondary metabolites with novel structures, diverse skeletons, and intriguing bioactivities due to their mutualistic symbiosis with hosts, and they have been considered as strategically significant medicinal microresources for the discovery of pharmaceutical lead compounds in the medicinal industry. They are also of great importance in the fundamental research field of natural product chemistry. In this work, we conducted a comprehensive review and systematic evaluation of the secondary metabolites of endolichenic fungi regarding their origin, distribution, structural characteristics, and biological activity, as well as recent advances in their medicinal applications, by summarizing research achievements since 2015. Moreover, the current research status and future research trends regarding their chemical components are discussed and predicted. A systematic review covering the fundamental chemical research advances and pharmaceutical potential of the secondary metabolites from endolichenic fungi is urgently required to facilitate our better understanding, and this review could also serve as a critical reference to provide valuable insights for the future research and promotion of natural products from endolichenic fungi.