Chuan Xiong

Neuroprotective effect of crude polysaccharide isolated from the fruiting bodies of Morchella importuna against H2O2-induced PC12 cell cytotoxicity by reducing oxidative stress

Oxidative stress played an essential role in neuronal cell injury through several apoptotic mechanisms associated with many neurodegenerative diseases. Reducing oxidative stress through antioxidants might be a possible strategy that could retard the diseases progression. In order to investigate the neuroprotective role of MIP (the crude polysaccharide extracted from the fruiting bodies of Morchella importuna), the antioxidative activity of MIP against the H2O2-induced cytotoxicity and the underlying preventative mechanisms in rat pheochromocytoma (PC12) cells were illustrated. It was shown that MIP could considerably enhance the viability of PC12 cells exposure to H2O2 and increased the activities of antioxidant enzyme like CAT, GSH-Px and SOD. It also reduced the content of malondialdehyde MDA and caspase-3 activation. In addition, MIP inhibited cell apoptosis via down-regulation of the NF-κB pathway and the p38-JNK pathway as well as activating of the extracellular signal-regulated kinase (ERK). Accordingly, MIP can be used as a promising neuroprotective compound for nervous diseases treatment.

Soil microbial communities of three major Chinese truffles in southwest China

Tuber pseudoexcavatum, Tuber sinoaestivum, and Tuber indicum are the 3 most important truffles growing in southeast China; however, their cultivation is still inefficient owing to the lack of understanding regarding the composition and function of the bacterial and fungal communities from the soils around the fruit bodies and the ectomycorrhiza of these truffles. The aim of this study was to disclose the microbial communities in truffle-producing soils in Huidong County, Sichuan, China, by using barcoded pyrosequencing. Approximately 350 000 quality-controlled sequences were obtained and grouped into 14 025 bacterial operational taxonomic units (OTUs) and 4385 fungal OTUs, which included 29 bacterial and 7 fungal phyla, respectively. The bacterial genus Acidobacterium and fungal genera Modicella, Pseudogymnoascus, and Mortierella were significantly more abundant in the control soils than in the truffle-producing soils (P < 0.05), while the bacterial genus Sphingomonas (Alphaproteobacteria) and arbuscular mycorrhizal fungal genus Glomus were significantly enriched in truffle-producing soil than in the control (P < 0.05), indicating their different roles within truffle grounds. Notably, some nonfungal organisms detected by 18S rDNA pyrosequencing were of high abundance, among which Cercozoa and Ochrophyta were significantly (P < 0.05) more abundant in truffle soils than in control soils, indicating their interactions with truffles.

Mineral constituents of a prized edible mushroom ( Tricholoma matsutake ) and soils beneath the fruiting bodies from the production areas across China

Fruiting bodies (500 g per site) of Tricholoma matsutake and the surface layer of soils collected from 20 spatially distant areas with pristine backgrounds across China were analyzed for potassium, magnesium, calcium, zinc, iron, copper, manganese and cadmium using inductively coupled plasma optical emission spectroscopy. In terms of the bioconcentration and bioexclusion concept, K, Mg, Zn, and Cu were highly bioconcentrated, and their bioconcentration factor values varied between 75-615, 2-107, 38-603 and 7-76, respectively, across the 20 sites. Fe, Mn and Cd were moderately bioconcentrated and their bioconcentration factors (BCFs) varied between 0.6-34.0, 0.4-37.0 and 0.9-7.0 respectively. However, Ca was excluded (BCF<1). T. matsutake is a species that is harvested in the wild as a valuable food and can contain a wide spectrum of both essential and hazardous mineral compounds that accumulate at elevated concentrations even if grown in pristine areas. The estimated intake rate of Cd in the fruiting bodies indicates cause for concern associated with this metal resulting from the daily consumption of between 200 and 400 g of fruiting bodies on a frequent basis during the mushrooming season.

Characterization and phylogenetic analysis of the complete mitochondrial genome of the medicinal fungus Laetiporus sulphureus

The medicinal fungus Laetiporus sulphureus is widely distributed worldwide. To screen for molecular markers potentially useful for phylogenetic analyses of this species and related species, the mitochondrial genome of L. sulphureus was sequenced and assembled. The complete circular mitochondrial genome was 101,111 bp long, and contained 38 protein-coding genes (PCGs), 2 rRNA genes, and 25 tRNA genes. Our BLAST search aligned about 6.1 kb between the mitochondrial and nuclear genomes of L. sulphureus, indicative of possible gene transfer events. Both the GC and AT skews in the L. sulphureus mitogenome were negative, in contrast to the other seven Polyporales species tested. Of the 15 PCGs conserved across the seven species of Polyporales, the lengths of 11 were unique in the L. sulphureus mitogenome. The Ka/Ks of these 15 PCGs were all less than 1, indicating that PCGs were subject to purifying selection. Our phylogenetic analysis showed that three single genes (cox1, cob, and rnl) were potentially useful as molecular markers. This study is the first publication of a mitochondrial genome in the family Laetiporaceae, and will facilitate the study of population genetics and evolution in L. sulphureus and other species in this family.

Tuber indicum shapes the microbial communities of ectomycorhizosphere soil and ectomycorrhizae of an indigenous tree (Pinus armandii)

The aim of this study was to investigate the effect of an ectomycorrhizal fungus (Tuber indicum) on the diversity of microbial communities associated with an indigenous tree, Pinus armandii, and the microbial communities in the surrounding ectomycorhizosphere soil. High-throughput sequencing was used to analyze the richness of microbial communities in the roots or rhizosphere of treatments with or without ectomycorrhizae. The results indicated that the bacterial diversity of ectomycorhizosphere soil was significantly lower compared with the control soil. Presumably, the dominance of truffle mycelia in ectomycorhizosphere soil (80.91%) and ectomycorrhizae (97.64%) was the main factor that resulted in lower diversity and abundance of endophytic pathogenic fungi, including Fusarium, Monographella, Ustilago and Rhizopus and other competitive mycorrhizal fungi, such as Amanita, Lactarius and Boletus. Bacterial genera Reyranena, Rhizomicrobium, Nordella, Pseudomonas and fungal genera, Cuphophyllus, Leucangium, Histoplasma were significantly more abundant in ectomycorrhizosphere soil and ectomycorrhizae. Hierarchical cluster analysis of the similarities between rhizosphere and ectomycorrhizosphere soil based on the soil properties differed significantly, indicating the mycorrhizal synthesis may have a feedback effect on soil properties. Meanwhile, some soil properties were significantly correlated with bacterial and fungal diversity in the rhizosphere or root tips. Overall, this work illustrates the interactive network that exists among ectomycorrhizal fungi, soil properties and microbial communities associated with the host plant and furthers our understanding of the ecology and cultivation of T. indicum.

The Genome Sequences of 90 Mushrooms

Macrofungus is defined as the fungus that grows an observable sporocarp. The sporocarps of many species are commonly called mushrooms and consumed by people all around the world as food and/or medicine. Most macrofungi belong to the divisions Basidiomycetes and Ascomycetes, which are estimated to contain more than 80,000 species in total. We report the draft genome assemblies of macrofungi (83 Basidiomycetes species and 7 Ascomycetes species) based on Illumina sequencing. The genome sizes of these species ranged from 27.4 Mb (Hygrophorus russula) to 202.2 MB (Chroogomphus rutilus). The numbers of protein-coding genes were predicted in the range of 9,511 (Hygrophorus russula) to 52,289 (Craterellus lutescens). This study provides the largest genomic dataset for macrofungi species. This resource will facilitate the artificial cultivation of edible mushrooms and the discovery of novel drug candidates.

Characterization and comparative mitogenomic analysis of six newly sequenced mitochondrial genomes from ectomycorrhizal fungi (Russula) and phylogenetic analysis of the Agaricomycetes

In this study, the mitochondrial genomes of six Russula species were sequenced using next generation sequencing. The six mitogenomes were all composed of circular DNA molecules, with lengths ranging from 40,961 bp to 69,423 bp. The length and number of protein coding genes (PCGs), GC content, AT skew, and GC skew varied among the six mitogenomes. The increased number and total size of introns likely contributed to the size expansion of mitogenomes in some Russula species. Gene synteny analysis revealed some gene rearrangements among the six mitochondrial genomes. The nad4L gene had the lowest K2P genetic distance of the 15 core PCGs among the six Russula species, indicating that this gene was highly conserved. The Ka/Ks values for all 15 core PCGs were <1, suggesting that they were all subject to purifying selection. Phylogenetic analyses based on two gene datasets (15 core PCGs, and 15 core PCGs + rnl + rns) recovered identical and well-supported trees. In addition, cox1 was identified as a potential single-gene molecular marker for the phylogenetic analysis of relationships among Agaricomycetes species. This study provides the first report of mitogenomes from the Russulaceae family and facilitates the investigation of population genetics and evolution of other ectomycorrhizal fungi.

Characterization of the mitochondrial genomes of three species in the ectomycorrhizal genus Cantharellus and phylogeny of Agaricomycetes

Cantharellus is a large ectomycorrhizal genus. Here, we assembled and annotated the mitochondrial genomes of C. lutescens, C. appalachiensis, and two specimens of C. cibarius. We found that all four mitochondrial genomes were circular and between 56,786 bp and 80,736 bp, long. The length and GC content of the protein-coding genes (PCGs) in the four mitogenomes varied. All tRNAs were folded into classical cloverleaf secondary structures; 16 of the 26 identified tRNAs contained variable sites across Cantharellus genus. C. appalachiensis was found containing the most repeated sequences (11.32% of the mitogenome), along with a substantial number of gene rearrangements. Comparative analysis of three C. cibarius specimens indicated that the mitogenomes of specimens from different regions differed. The Ka/Ks ratios of all 15 PCGs identified across all four mitogenomes were <1, indicating that these genes have been subject to purifying selection. Phylogenetic analysis recovered a well-supported tree based on a combined analysis of the 15 PCGs. In addition, we identified cob, cox1, and rnl as potential single-gene markers for the analysis of phylogenetic relationships among Agaricomycetes species. The mitogenomes reported in this study will facilitate the study of population genetics and evolution in Cantharellus and other closely related species.

Characterization and comparison of the mitochondrial genomes from two Lyophyllum fungal species and insights into phylogeny of Agaricomycetes

Lyophyllum decastes and Lyophyllum shimeji are the two primary species within the L. decastes complex, and they differ considerably in their nutritional lifestyles and preferred growth environments. However, differences in their mitogenomes have not yet been investigated. In this study, the mitogenomes of the two species were sequenced by next-generation sequencing technology, successfully assembled, and compared. The two mitogenomes of L. decastes and L. shimeji comprised circular DNA molecules of sizes 50,643 bp and 73,678 bp, respectively. The lengths and base compositions of their core protein coding genes (PCGs) and tRNA genes varied considerably between the two mitogenomes. Further, gene collinearity analysis indicated a large-scale gene rearrangement between the two mitogenomes. Of the 15 core PCGs, the genetic distance of the atp9 gene was the smallest between the two species, indicating that this gene was highly conserved in the two Lyophyllum species. Phylogenetic analysis based on a combined mitochondrial gene dataset resulted in a well-supported topology, wherein the two Lyophyllum species were most closely related to Tricholoma matsutake. This study represents the first report of mitogenomes for the Lyophyllum genus. As such, the results will provide a basis for understanding the differentiation and evolution of mitogenomes in the Lyophyllum genus.

Characterization and comparative analysis of six complete mitochondrial genomes from ectomycorrhizal fungi of the Lactarius genus and phylogenetic analysis of the Agaricomycetes

Lactarius is one of the most prominent genera of mushroom-forming fungi in the world. In the present study, complete mitochondrial genomes (mitogenomes) from six Lactarius species were sequenced and assembled. The six mitogenomes were all composed of circular DNA molecules, with total lengths ranging from 38,445 bp to 60,843 bp. The GC contents, GC skews, and AT skews of the mitogenomes varied among the six species. Mitogenomic synteny analysis revealed the presence of gene rearrangements among the mitogenomes. Among the 15 core protein coding genes (PCGs) within the mitogenomes, nad4L exhibited the least genetic distance among species, indicating a high degree of conservation. In addition, the Ka/Ks values for all 15 core PCGs were <1, suggesting that they were subject to purifying selection. Comparative analyses indicated that the increase of intron numbers and sizes contributed to the expansion of mitogenomes in Lactarius. Phylogenetic analyses based on three combined gene datasets yielded identical and well-supported (BPP ≥ 0.83) topologies, dividing the six Lactarius species into two groups. This study provides the first report of mitogenomes from Lactarius and promotes further understanding of the genetics, evolution, and phylogenetic relationships of this important ectomycorrhizal fungal genus.