Community Assembly of Fungi and Bacteria along Soil-Plant Continuum Differs in a Zoige Wetland.

Distinct plant associated microbiomes live in rhizosphere soil, roots, and leaves. However, the differences in community assembly of fungi and bacteria along soil-plant continuum are less documented in ecosystems. We examined fungal and bacterial communities associated with leaves, roots, and rhizosphere soil of the dominant arbuscular mycorrhizal (AM) plants Taraxacum mongolicum and Elymus nutans and non-AM plant Carex enervis in the Zoige Wetland by using high throughput sequencing techniques. The operational taxonomic unit (OTU) richness of fungi and bacteria was significantly higher in rhizosphere soil than in roots and leaves, and their community compositions were significantly different in the rhizosphere soil, roots, and leaves in each plant species. The co-occurrence network analysis revealed that the sensitive fungal and bacterial OTUs with various taxonomic positions were mainly clustered into different modules according to rhizosphere soil, roots, and leaves in each plant species. Along the soil-plant continuum, the rhizosphere soil pool contributed more source on bacterial than on fungal communities in roots and leaves of the three plant species, and more source on bacterial and fungal communities in leaves of T. mongolicum and E. nutans compared with C. enervis. Furthermore, the root pool contributed more source on bacterial than on fungal communities in leaves of T. mongolicum and E. nutans but not that of C. enervis. This study highlights that the host plant selection intensity is higher in fungal than in bacterial communities in roots and leaves from rhizosphere soil in each plant species, and differs in fungal and bacterial communities along the soil-plant continuum in AM plants T. mongolicum and E. nutans and non-AM plant C. enervis in the Zoige Wetland. IMPORTANCE Elucidating the community microbiome assemblage alone the soil-plant continuum will help to better understand the biodiversity maintenance and ecosystem functioning. Here, we examined the fungal and bacterial communities in rhizosphere soil, roots, and leaves of two dominant AM plants and a non-AM plant in Zoige Wetland. We found that along the soil - plant continuum, host plant selection intensity is higher in fungal than in bacterial communities in roots and leaves from rhizosphere soil in each plant species, and differs in fungal and bacterial communities in the AM- and non-AM plants. This is the first report provides evidence of different assembly patterns of fungal and bacterial communities along the soil-plant continuum in the AM- and non-AM plants in the Zoige Wetland.

Plants Play Stronger Effects on Soil Fungal than Bacterial Communities and Co-Occurrence Network Structures in a Subtropical Tree Diversity Experiment.

Increasing biodiversity loss profoundly affects community structure and ecosystem functioning. However, the differences in community assembly and potential drivers of the co-occurrence network structure of soil fungi and bacteria in association with tree species richness gradients are poorly documented. Here, we examined soil fungal and bacterial communities in a Chinese subtropical tree species richness experiment (from 1 to 16 species) using amplicon sequencing targeting the internal transcribed spacer 2 and V4 hypervariable region of the rRNA genes, respectively. Tree species richness had no significant effect on the diversity of either fungi or bacteria. In addition to soil and spatial distance, tree species richness and composition had a significant effect on fungal community composition but not on bacterial community composition. In fungal rather than bacterial co-occurrence networks, the average degree, degree centralization, and clustering coefficient significantly decreased, but the modularity significantly increased with increasing tree species richness. Fungal co-occurrence network structure was influenced by tree species richness and community composition as well as the soil carbon: nitrogen ratio, but the bacterial co-occurrence network structure was affected by soil pH and spatial distance. This study demonstrates that the community assembly and potential drivers of the co-occurrence network structure of soil fungi and bacteria differ in the subtropical forest. IMPORTANCE Increasing biodiversity loss profoundly affects community structure and ecosystem functioning. Therefore, revealing the mechanisms associated with community assembly and co-occurrence network structure of microbes along plant species diversity gradients is very important for understanding biodiversity maintenance and community stability in response to plant diversity loss. Here, we compared the differences in community assembly and potential drivers of the co-occurrence network structure of soil fungi and bacteria in a subtropical tree diversity experiment. In addition to soil and spatial distance, plants are more strongly predictive of the community and co-occurrence network structure of fungi than those of bacteria. The study highlighted that plants play more important roles in shaping community assembly and interactions of fungi than of bacteria in the subtropical tree diversity experiment.

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.

Soil fungal diversity and community assembly: affected by island size or type?

Fungi have a huge biodiversity and play important roles in soil biogeochemical cycling in island ecosystems. Although island biogeography has been widely studied for macroorganisms, fungal community assembly in true islands and its relationship with island area are less documented. We examined soil fungal communities in 18 oceanic islands of two types (eight non-coral islands and 10 coral islands) using the Illumina MiSeq sequencing technique. Our results showed that fungal α-diversity (species richness) was substantially different among the oceanic islands, with a higher value in non-coral islands than in coral islands. Fungal α-diversity was significantly affected by soil potassium and magnesium (Mg) and plant communities in non-coral islands, whereas only soil Mg significantly affected it in coral islands. Soil fungal community composition was significantly different in the non-coral and coral islands and was influenced by soil property, plant community and spatial distance. The ecological stochasticity model showed that the fungal community assembly was mainly governed by deterministic processes regardless of island type. Fungal ß-diversity, but not α-diversity, increased significantly with increasing island area. These findings have implications for the better prediction of soil fungal community dynamics in island systems and biodiversity conservation in fragmented habitats.

Interleukin-27 Suppresses T Helper-17 Inflammation in Allergic Rhinitis.

BACKGROUND: T helper 17 (Th17) cells and the related cytokines, interleukin (IL)- 17 and IL-23, were proved to play pivotal roles during the development of allergic rhinitis (AR). IL-27, an anti-inflammatory cytokine, has been reported to promote the production of IL-12R and induce Th1 cell responses. However, its effect on Th17 responses was not fully understood. OBJECTIVE: We conducted the present research to explore the role of IL-27 in the regulation of Th17 responses in AR. METHODS: Thirty confirmed AR patients and 20 controls were recruited for the study. The mRNA expression and protein levels of IL-27 were analyzed employing quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively, and their correlations with Th17 cytokines were analyzed. We utilized ELISA and qPCR to analyze the effect of IL-27 on the differentiation of Th17 cells and the production of IL-17 and IL-23 from peripheral blood mononuclear cells (PBMCs). RESULTS: We found that the IL-27 levels in AR were downregulated and negatively related to IL-17 and IL-23 levels. The recombinant IL-27 inhibited the mRNA expression of RORγt and the protein expression of IL-17 and IL-23 in PBMCs through MEK, NF-κB, and JNK pathways. CONCLUSION: Our data demonstrated that IL-27 suppressed Th17 responses through MEK, NF-κB, and JNK pathways.

Interleukin-27 inhibits helper T cell type-2 response in allergic rhinitis.

OBJECTIVE: Interleukin-27 (IL-27) is a recently identified cytokine which plays both pro-inflammatory and anti-inflammatory effect in different diseases. However, its function in the pathogenesis of allergic rhinitis (AR) was not clear so far. METHODS: Quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA) were performed to detect the expression of interleukin 27 (IL-27) and Th2 cytokines (IL-4, IL-5, IL-13) from 22 patients diagnosed with AR and 20 normal controls. Purified peripheral blood mononuclear cells (PBMCs) were prepared for in vitro experiment. RESULTS: Serum mRNA and protein levels of IL-27 were down-regulated in AR patients compared with normal controls. The expression of IL-27 showed negative correlation with Th2 cytokines. In vitro study showed that IL-27 significantly inhibited Th2 cytokines expression from PBMCs. CONCLUSION: Our results suggested that decreased IL-27 expression in AR were correlated with Th2 response. IL-27 may be used as potential target in the future treatment of AR.