Genomic and Proteomic Analyses of the Fungus Arthrobotrys oligospora Provide Insights into Nematode-Trap Formation

Nematode-trapping fungi are “carnivorous” and attack their hosts using specialized trapping devices. The morphological development of these traps is the key indicator of their switch from saprophytic to predacious lifestyles. Here, the genome of the nematode-trapping fungus Arthrobotrys oligospora Fres. (ATCC24927) was reported. The genome contains 40.07 Mb assembled sequence with 11,479 predicted genes. Comparative analysis showed that A. oligospora shared many more genes with pathogenic fungi than with non-pathogenic fungi. Specifically, compared to several sequenced ascomycete fungi, the A. oligospora genome has a larger number of pathogenicity-related genes in the subtilisin, cellulase, cellobiohydrolase, and pectinesterase gene families. Searching against the pathogen-host interaction gene database identified 398 homologous genes involved in pathogenicity in other fungi. The analysis of repetitive sequences provided evidence for repeat-induced point mutations in A. oligospora. Proteomic and quantitative PCR (qPCR) analyses revealed that 90 genes were significantly up-regulated at the early stage of trap-formation by nematode extracts and most of these genes were involved in translation, amino acid metabolism, carbohydrate metabolism, cell wall and membrane biogenesis. Based on the combined genomic, proteomic and qPCR data, a model for the formation of nematode trapping device in this fungus was proposed. In this model, multiple fungal signal transduction pathways are activated by its nematode prey to further regulate downstream genes associated with diverse cellular processes such as energy metabolism, biosynthesis of the cell wall and adhesive proteins, cell division, glycerol accumulation and peroxisome biogenesis. This study will facilitate the identification of pathogenicity-related genes and provide a broad foundation for understanding the molecular and evolutionary mechanisms underlying fungi-nematodes interactions

Calycosin Suppresses Epithelial Derived Initiative Key Factors and Maintains Epithelial Barrier in Allergic Inflammation via TLR4 Mediated NF-κB Pathway

Background/Aims: Calycosin is a bioactive component of Astragali Radix, a Chinese herb for treating allergy. We have previously demonstrated that calycosin effectively inhibited allergic inflammation efficiently. The aim of this study was to explore the mechanism of calycosin on epithelial cells in allergic inflammation. Methods: An initial stage of atopic dermatitis (AD) model in which mice were just sensitized with FITC, was established in vivo and immortalized human keratinocytes (HaCaT cells) were utilized in vitro. Initiative key cytokines, TSLP and IL-33, were measured by ELISA, qPCR, immunofluorescence and Western blot. The junctions in epithelial cells were observed by electron microscopy and tight junctions (TJs) (Occludin and ZO-1) were assessed by Western blot and immunofluorescence. TLR4, MyD88, TAK1, TIRAP and NF-κB were measured by qPCR or Western blot. Results: The results showed that TSLP and IL-33 were inhibited significantly by calycosin in the initial stage of AD model. Simultaneously, calycosin attenuated the separated gap among the epithelial cells and increased the expression of TJs. TSLP/IL-33 and TJs were similarly affected in LPS-stimulated HaCaT cells in vitro. Meanwhile, calycosin not only inhibited the expressions of TLR4, MyD88, TAK1 and TIRAP, but also reduced NF-κB activation in vitro and in vivo. An NF-κB inhibitor enhanced the expressions of TJs and reduced that of TSLP/IL-33 in LPS-stimulated HaCaT cells. Conclusion: These results indicated that calycosin reduced the secretion of TSLP/IL-33 and attenuated the disruption of epithelial TJs by inhibiting TLR4 mediated NF-κB signaling pathway. These findings help to understand the beneficial effects of calycosin on AD, and to develop effective preventive or therapeutic strategies to combat this disease and other epithelial barrier deletion-mediated allergic diseases