New sesquiterpenoids from Biscogniauxia sp.

Five new sesquiterpenoids, including a campherenane-type (1), a bergamotane-type (2), a drimane-type (3), and two bisabolane-type (5-6) sesquiterpenoids have been isolated from Biscogniauxia sp. 71-10-1-1. Their structures were determined by spectroscopic analyses, quantum chemical ECD calculations,13C chemical shifts calculations, and X-ray crystallography. This is the first report of campherenane-type and drimane-type sesquiterpenoids from Biscogniauxia. Furthermore, the anti-inflammatory assays of all compounds are evaluated, and the results showed that compounds 3 and 7 exhibited the effects against the production of the pro-inflammatory cytokine TNF-α.

Tree mycorrhizal type and tree diversity shape the forest soil microbiota.

There is limited knowledge on how the association of trees with different mycorrhizal types shapes soil microbial communities in the context of changing tree diversity levels. We used arbuscular (AM) and ectomycorrhizal (EcM) tree species as con- and heterospecific tree species pairs (TSPs), which were established in plots of three tree diversity levels including monocultures, two-species mixtures and multi-tree species mixtures in a tree diversity experiment in subtropical China. We found that the tree mycorrhizal type had a significant effect on fungal but not bacterial alpha diversity. Furthermore, only EcM but not AM TSPs fungal alpha diversity increased with tree diversity, and the differences between AM and EcM TSPs disappeared in multi-species mixtures. Tree mycorrhizal type, tree diversity and their interaction had significant effects on fungal community composition. Neither fungi nor bacteria showed any significant compositional variation in TSPs located in multi-species mixtures. Accordingly, the most influential taxa driving the tree mycorrhizal differences at low tree diversity were not significant in multi-tree species mixtures. Collectively, our results indicate that tree mycorrhizal type is an important factor determining the diversity and community composition of soil microbes, and higher tree diversity levels promote convergence of the soil microbial communities. SIGNIFICANCE STATEMENT: More than 90% of terrestrial plants have symbiotic associations with mycorrhizal fungi which could influence the coexisting microbiota. Systematic understanding of the individual and interactive effects of tree mycorrhizal type and tree species diversity on the soil microbiota is crucial for the mechanistic comprehension of the role of microbes in forest soil ecological processes. Our tree species pair (TSP) concept coupled with random sampling within and across the plots, allowed us the unbiased assessment of tree mycorrhizal type and tree diversity effects on the tree-tree interaction zone soil microbiota. Unlike in monocultures and two-species mixtures, we identified species-rich and converging fungal and bacterial communities in multi-tree species mixtures. Consequently, we recommend planting species-rich mixtures of EcM and AM trees, for afforestation and reforestation regimes. Specifically, our findings highlight the significance of tree mycorrhizal type in studying 'tree diversity - microbial diversity - ecosystem function' relationships.

Nitrogen fertilisation disrupts the temporal dynamics of arbuscular mycorrhizal fungal hyphae but not spore density and community composition in a wheat field.

Elucidating the temporal dynamics of arbuscular mycorrhizal (AM) fungi is critical for understanding their functions. Furthermore, research investigating the temporal dynamics of AM fungi in response to agricultural practices remains in its infancy. We investigated the effect of nitrogen fertilisation and watering reduction on the temporal dynamics of AM fungi, across the lifespan of wheat. Nitrogen fertilisation decreased AM fungal spore density (SD), extraradical hyphal density (ERHD), and intraradical colonisation rate (IRCR) in both watering conditions. Nitrogen fertilisation affected AM fungal community composition in soil but not in roots, regardless of watering conditions. The temporal analysis revealed that AM fungal ERHD and IRCR were higher under conventional watering and lower under reduced watering in March than in other growth stages at low (≤ 70 kg N ha-1 yr-1 ) but not at high (≥ 140) nitrogen fertilisation levels. AM fungal SD was lower in June than in other growth stages and community composition varied with plant development at all nitrogen fertilisation levels, regardless of watering conditions. This study demonstrates that high nitrogen fertilisation levels disrupt the temporal dynamics of AM fungal hyphal growth but not sporulation and community composition.

Assembly processes lead to divergent soil fungal communities within and among 12 forest ecosystems along a latitudinal gradient.

Latitudinal gradients provide opportunities to better understand soil fungal community assembly and its relationship with vegetation, climate, soil and ecosystem function. Understanding the mechanisms underlying community assembly is essential for predicting compositional responses to changing environments. We quantified the relative importance of stochastic and deterministic processes in structuring soil fungal communities using patterns of community dissimilarity observed within and between 12 natural forests and related these to environmental variation within and among sites. The results revealed that whole fungal communities and communities of arbuscular and ectomycorrhizal fungi consistently exhibited divergent patterns but with less divergence for ectomycorrhizal fungi at most sites. Within those forests, no clear relationships were observed between the degree of divergence within fungal and plant communities. When comparing communities at larger spatial scales, among the 12 forests, we observed distinct separation in all three fungal groups among tropical, subtropical and temperate climatic zones. Soil fungal ß-diversity patterns between forests were also greater when comparing forests exhibiting high environmental heterogeneity. Taken together, although large-scale community turnover could be attributed to specific environmental drivers, the differences among fungal communities in soils within forests was high even at local scales.

Diisoprenyl-cyclohexene/ane-Type Meroterpenoids from Biscogniauxia sp. and Their Anti-inflammatory Activities.

A secondary metabolites investigation on Biscogniauxia sp. 71-10-1-1 was carried out, which led to the obtention of nine new diisoprenyl-cyclohexene/ane-type meroterpenoids (1-9) and two new isoprenylbenzoic acid-type meroterpeniods (10-11). The structures of these isolates were established on the basis of multispectroscopic analyses, ECD, and 13C chemical shifts calculations, and single-crystal X-ray diffraction. Among them, biscognin A (1) is the first diisoprenyl-cyclohexene-type meroterpenoid with a unique 2-isopropyl-6'-methyloctahydro-1'H-spiro[cyclopropane-1,2'-naphthalene] skeleton. Biscognienyne F (5) is the first diisoprenyl-cyclohexene-type meroterpenoid with a cyclic carbonate. The anti-inflammatory assays of the majority of compounds were evaluated, which exhibited that compounds 3 and 5 can obviously inhibit pro-inflammatory cytokines TNF-α and IL-6 productions. This is the first report for diisoprenyl-cyclohexene-type meroterpenoids with anti-inflammatory activity. Moreover, the possible biogenetic pathways of the majority of compounds (1-5) are proposed.

Relationships between soil fungal and woody plant assemblages differ between ridge and valley habitats in a subtropical mountain forest.

Elucidating interactions of above-ground and below-ground communities in different habitat types is essential for understanding biodiversity maintenance and ecosystem functioning. Using 454 pyrosequencing of ITS2 sequences we examined the relationship between subtropical mountain forest soil fungal communities, abiotic conditions, and plant communities using correlation and partial models. Ridge and valley habitats with differing fungal communities were delineated. Total, saprotrophic and pathogenic fungal richness were significantly correlated with plant species richness and/or soil nutrients and moisture in the ridge habitat, but with habitat convexity or basal area of Castanopsis eyrei in the valley habitat. Ectomycorrhizal (EM) fungal richness was significantly correlated with basal area of C. eyrei and total EM plants in the ridge and valley habitats, respectively. Total, saprotrophic, pathogenic and EM fungal compositions were significantly correlated with plant species composition and geographic distance in the ridge habitat, but with various combinations of plant species composition, plant species richness, soil C : N ratio and pH or no variables in the valley habitat. Our findings suggest that mechanisms influencing soil fungal diversity and community composition differ between ridge and valley habitats, and relationships between fungal and woody plant assemblages depend on habitat types in the subtropical forest ecosystem.

Phylogenetic relatedness explains highly interconnected and nested symbiotic networks of woody plants and arbuscular mycorrhizal fungi in a Chinese subtropical forest.

Elucidating symbiotic relationships between arbuscular mycorrhizal fungi (AMF) and plants contributes to a better understanding of their reciprocally dependent coexistence and community assembly. However, the main drivers of plant and AMF community assembly remain unclear. In this study, we examined AMF communities from 166 root samples of 17 woody plant species from 10 quadrats in a Chinese subtropical forest using 454 pyrosequencing of 18S rRNA gene to describe symbiotic AMF-plant association. Our results show the woody plant-AMF networks to be highly interconnected and nested, but in antimodular and antispecialized manners. The nonrandom pattern in the woody plant-AMF network was explained by plant and AMF phylogenies, with a tendency for a stronger phylogenetic signal by plant than AMF phylogeny. This study suggests that the phylogenetic niche conservatism in woody plants and their AMF symbionts could contribute to interdependent AMF and plant community assembly in this subtropical forest ecosystem.

Plant Identity Exerts Stronger Effect than Fertilization on Soil Arbuscular Mycorrhizal Fungi in a Sown Pasture.

Arbuscular mycorrhizal (AM) fungi play key roles in plant nutrition and plant productivity. AM fungal responses to either plant identity or fertilization have been investigated. However, the interactive effects of different plant species and fertilizer types on these symbiotic fungi remain poorly understood. We evaluated the effects of the factorial combinations of plant identity (grasses Avena sativa and Elymus nutans and legume Vicia sativa) and fertilization (urea and sheep manure) on AM fungi following 2-year monocultures in a sown pasture field study. AM fungal extraradical hyphal density was significantly higher in E. nutans than that in A. sativa and V. sativa in the unfertilized control and was significantly increased by urea and manure in A. sativa and by manure only in E. nutans, but not by either fertilizers in V. sativa. AM fungal spore density was not significantly affected by plant identity or fertilization. Forty-eight operational taxonomic units (OTUs) of AM fungi were obtained through 454 pyrosequencing of 18S rDNA. The OTU richness and Shannon diversity index of AM fungi were significantly higher in E. nutans than those in V. sativa and/or A. sativa, but not significantly affected by any fertilizer in all of the three plant species. AM fungal community composition was significantly structured directly by plant identity only and indirectly by both urea addition and plant identity through soil total nitrogen content. Our findings highlight that plant identity has stronger influence than fertilization on belowground AM fungal community in this converted pastureland from an alpine meadow.

A New Xanthone Glycoside from the Endolichenic Fungus Sporormiella irregularis.

A new xanthone glycoside, sporormielloside (1), was isolated from an EtOAc extract of an endolichenic fungal strain Sporormiella irregularis (No. 71-11-4-1), along with two known xanthones (2, 3). Their structures were determined by detailed spectroscopic analysis (IR, MS, and 1D- and 2D-NMR), a chemical method, and a comparison of NMR data with closely related compounds previously reported. According to the structures of isolated compounds, their plausible biosynthetic pathway was deduced.

Community assembly of ectomycorrhizal fungi along a subtropical secondary forest succession.

Environmental selection and dispersal limitation are two of the primary processes structuring biotic communities in ecosystems, but little is known about these processes in shaping soil microbial communities during secondary forest succession. We examined the communities of ectomycorrhizal (EM) fungi in young, intermediate and old forests in a Chinese subtropical ecosystem, using 454 pyrosequencing. The EM fungal community consisted of 393 operational taxonomic units (OTUs), belonging to 21 EM fungal lineages, in which three EM fungal lineages and 11 EM fungal OTUs showed significantly biased occurrence among the young, intermediate and old forests. The EM fungal community was structured by environmental selection and dispersal limitation in old forest, but only by environmental selection in young, intermediate, and whole forests. Furthermore, the EM fungal community was affected by different factors in the different forest successional stages, and the importance of these factors in structuring EM fungal community dramatically decreased along the secondary forest succession series. This study suggests that different assembly mechanisms operate on the EM fungal community at different stages in secondary subtropical forest succession.

Nodulisporiviridins A-H, Bioactive Viridins from Nodulisporium sp.

Eight new viridins, nodulisporiviridins A-H (1-8), were isolated from the extract of an endolichenic fungal strain Nodulisporium sp. (No. 65-17-2-1) that was fermented with potato-dextrose broth. The structures were determined using spectroscopic and X-ray crystallographic analysis. Nodulisporiviridins A-D (1-4) are unique viridins with an opened ring A. The Aß42 aggregation inhibitory activities of 1-8 were evaluated using a thioflavin T (ThT) assay with epigallocatechin gallate (EGCG) as the positive control (EGCG IC50 of 0.5 µM). Nodulisporiviridin G (7) displayed potent inhibitory activity with an IC50 value of 1.2 µM, and the preliminary trend of activity of these viridins as Aß42 aggregation inhibitors was proposed. The short-term memory assay on an Aß transgenic drosophila model of Alzheimer's disease showed that all eight compounds improved the short-term memory capacity, with potencies close to that of the positive control (memantine).

Arbuscular mycorrhizal fungal community response to warming and nitrogen addition in a semiarid steppe ecosystem.

Understanding the response of arbuscular mycorrhizal (AM) fungi to warming and nitrogen (N) fertilization is critical to assess the impact of anthropogenic disturbance on ecosystem functioning under global climate change scenarios. In this study, AM fungal communities were examined in a full factorial design with warming and N addition in a semiarid steppe in northern China. Warming significantly increased AM fungal spore density, regardless of N addition, whilst N addition significantly decreased AM fungal extraradical hyphal density, regardless of warming. A total of 79 operational taxonomic units (OTUs) of AM fungi were recovered by 454 pyrosequencing of SSU rDNA. Warming, but not N addition, had a significant positive effect on AM fungal OTU richness, while warming and N addition significantly increased AM fungal Shannon diversity index. N addition, but not warming, significantly altered the AM fungal community composition. Furthermore, the changes in AM fungal community composition were associated with shifts in plant community composition indirectly caused by N addition. These findings highlight the different effects of warming and N addition on AM fungal communities and contribute to understanding AM fungal community responses to global environmental change scenarios in semiarid steppe ecosystems.

Cyclohexenones and isocoumarins from an endophytic fungus of Sarcosomataceae sp.

Three new cyclohexenones (1-3, named sarcosones A-C) and two new isocoumarins (4 and 5), together with five known isocoumarins (6-10), were isolated from the solid cultures of an endophytic fungus Sarcosomataceae sp. NO.49-14-2-1. Their chemical structures were elucidated by analyses of HR-ESI-TOF-MS, (1)H, (13)C NMR, (1)H-(1)H COSY, HSQC, and HMBC spectra. Their absolute configurations were determined via modified Mosher's method and circular dichroism spectra method.

Nodulisporipyrones A-D, new bioactive α-pyrone derivatives from Nodulisporium sp.

Four new α-pyrone derivatives, nodulisporipyrones A-D (1-4), were isolated from the extract of an endolichenic fungal strain Nodulisporium sp. (65-12-7-1) that was fermented with rice. The structures of 1-4 were elucidated by extensive spectroscopic analysis, and the absolute configurations were determined by modified Mosher's method and electronic circular dichroism experiments. Their antimicrobial activities against Staphylococcus aureus 209P, Escherichia coli ATCC0111, Aspergillus niger R330, and Candida albicans FIM709 were evaluated using a paper disk diffusion method. Nodulisporipyrones A-D (1-4) are the first α-pyrone derivatives from Nodulisporium fungi.

New α-pyrone and phthalide from the Xylariaceae fungus.

A new α-pyrone xylaripyrone A (1) and a new phthalide xylariphthalide A (2) were isolated from the Xylariaceae fungus (no. 63-19-7-3), along with four related known phthalides (3-6): 4-[(acetyloxy)methyl]-7-methoxy-6-methyl-1(3H)-isobenzofuranone (3), convolvulol (4), 7-methoxy-4,6-dimethyl-3H-isobenzofuran-1-one (5), and convolvulanic acid B (6). Their structures were determined on the basis of IR, MS, and NMR spectroscopic analyses.

Pericoterpenoid A, a new bioactive cadinane-type sesquiterpene from Periconia sp.

Pericoterpenoid A (1), a new cadinane-type sesquiterpene, was isolated from an endolichenic fungal strain Periconia sp. (No. 19-4-2-1). Its structure was characterized by analyzing the spectroscopic data (IR, MS, 1D- and 2D-NMR). The antimicrobial activity against Escherichia coli, Staphylococcus aureus, Aspergillus niger, and Candida albicans was evaluated. Pericoterpenoid A showed moderate antimicrobial activity against A. niger and weak activity against C. albicans. This is the first report of the presence of cadinane-type sesquiterpene in Periconia sp.

Host plant richness explains diversity of ectomycorrhizal fungi: Response to the comment of Tedersoo et al. (2014).

Exploring the relationships between the biodiversity of groups of interacting organisms yields insight into ecosystem stability and function (Hooper et al. ; Wardle ). We demonstrated positive relationships between host plant richness and ectomycorrhizal (EM) fungal diversity both in a field study in subtropical China (Gutianshan) and in a meta-analysis of temperate and tropical studies (Gao et al. ). However, based on re-evaluation of our data sets, Tedersoo et al. () argue that the observed positive correlation between EM fungal richness and EM plant richness at Gutianshan and also in our metastudies was based mainly from (i) a sampling design with inconsistent species pool and (ii) poor data compilation for the meta-analysis. Accordingly, we checked our data sets and repeated the analysis performed by Tedersoo et al. (). In contrast to Tedersoo et al. (), our re-analysis still confirms a positive effect of plant richness on EM fungal diversity in Gutianshan, temperate and tropical ecosystems, respectively.

Different mechanisms underlie similar species-area relationships in two tropical archipelagoes.

Despite much research in the field of island biogeography, mechanisms regulating insular diversity remain elusive. Here, we aim to explore mechanisms underlying plant species-area relationships in two tropical archipelagoes in the South China Sea. We found positive plant species-area relationships for both coral and continental archipelagoes. However, our results showed that different mechanisms contributed to similar plant species-area relationships between the two archipelagoes. For coral islands, soil nutrients and spatial distance among communities played major roles in shaping plant community structure and species diversity. By contrast, the direct effect of island area, and to a lesser extent, soil nutrients determined plant species richness on continental islands. Intriguingly, increasing soil nutrients availability (N, P, K) had opposite effects on plant diversity between the two archipelagoes. In summary, the habitat quality effect and dispersal limitation are important for regulating plant diversity on coral islands, whereas the passive sampling effect, and to a lesser extent, the habitat quality effect are important for regulating plant diversity on continental islands. More generally, our findings indicate that island plant species-area relationships are outcomes of the interplay of both niche and neutral processes, but the driving mechanisms behind these relationships depends on the type of islands.

Host plant genus-level diversity is the best predictor of ectomycorrhizal fungal diversity in a Chinese subtropical forest.

Microbial diversity is generally far higher than plant diversity, but the relationship between microbial diversity and plant diversity remains enigmatic. To shed light on this problem, we examined the diversity of a key guild of root-associated microbes,that is, ectomycorrhizal (EM) fungi along a plant diversity gradient in a Chinese subtropical forest. The results indicated that EM fungal diversity was positively correlated with host plant diversity. Furthermore, this relationship was best predicted by host genus-level diversity, rather than species-level diversity or family-level diversity. The generality of this finding was extended beyond our study system through the analyses of 100 additional studies of EM fungal communities from tropical and temperate forests.Here as well, EM fungal lineage composition was significantly affected by EM plant diversity levels, and some EM fungal lineages were co-associated with some host plant genera. These results suggest a general diversity maintenance mechanism for host-specific microbes based on higher order host plant phylogenetic diversity.

Pleurospiroketals A-E, perhydrobenzannulated 5,5-spiroketal sesquiterpenes from the edible mushroom Pleurotus cornucopiae.

Five novel perhydrobenzannulated 5,5-spiroketal sesquiterpenes, namely, pleurospiroketals A-E (1-5), were isolated from the culture of the edible mushroom Pleurotus cornucopiae. Pleurospiroketals D (4) and E (5) were obtained as an isomeric mixture with a ratio of 5:4. Their structures were established by NMR, X-ray single-crystal diffraction, and CD data analysis. Pleurospiroketals A-E (1-5) are sesquiterpenoids with a unique benzannulated 5,5-spiroketal skeleton. Compounds 1-3 showed inhibitory activity against nitric oxide production in lipopolysaccharide-activated macrophages with IC(50) values of 6.8, 12.6, and 20.8 µM, respectively.