Rapid and simple preparation of mushroom DNA directly from colonies and fruiting bodies for PCR

Physiological function of hydrophobin Hydph16 in cell wall formation in agaricomycete Pleurotus ostreatus

Hydrophobins are small-secreted proteins with both hydrophobic and hydrophilic regions, enabling the mycelium to break through the air-medium interface by reducing the medium surface tension. Over 20 putative hydrophobin-encoding genes have been predicted in the agaricomycete Pleurotus ostreatus. Three hydrophobin-encoding genes, vmh2, vmh3, and hydph16, were predominantly expressed in the vegetative mycelium. Despite these common properties, we have previously demonstrated the distinct functions of Vmh2 and Vmh3 in environmental stress resistance. In this study, we focused on hydph16 and found that Δhydph16 strains had sparser aerial mycelium than control strains. The cell wall thickness of Δhydph16 strains reduced by 40 % compared to that of control strains, but no significant differences were found in the relative chitin and glucan percentages or relative putative cell wall synthesis-related gene expression levels. Furthermore, unlike vmh2 and vmh3, hydph16 deletion did not change the hydrophobicity of the aerial mycelium. This study is the first to report that the lack of hydrophobin can lead to a significant change in aerial hyphae cell wall formation without altering the major cell wall polysaccharide composition. Additionally, this study revealed multiple roles for Hydph16, distinct from those of other highly expressed hydrophobins, Vmh2 and Vmh3. These results suggested that agaricomycetes, including P. ostreatus, have evolved to possess multiple hydrophobins with different functions.

Role of putative APSES family transcription factor Swi6 in cell wall synthesis regulation in the agaricomycete Pleurotus ostreatus

Clade A APSES family transcription factor Swi6 functions alongside Mbp1 to form the MBF (MluI cell cycle box-binding factor) complex in ascomycetes. In the agaricomycete Pleurotus ostreatus, Mbp1 plays a crucial role in regulating β-glucan and chitin synthesis; however, the role of Swi6 has not been explored in this fungus. In this study, its involvement in cell wall synthesis regulation was analysed using swi6 disruption strains in P. ostreatus. The Δswi6 strains exhibited reduced growth rates and shorter aerial hyphae formation in both agar and liquid media, suggesting an essential role of Swi6 in normal vegetative growth. Furthermore, swi6 disruption affected cell wall thickness distribution, the expression of specific chitin synthase genes, the relative percentage of chitin, and sensitivity to calcofluor white, suggesting that Swi6 is required for normal chitin synthesis regulation in P. ostreatus. In contrast, no significant differences were observed between the wild-type and Δswi6 strains in the relative percentage of α- and β-glucan and the expression of α- and β-glucan synthase genes, suggesting its unimportant role in α- and β-glucan synthesis regulation. In conclusion, Swi6 is necessary for normal mycelial growth and chitin synthesis regulation in P. ostreatus. To the best of our knowledge, this study is the first report on the functional differences and overlaps between Mbp1 and Swi6 in the regulation of cell wall synthesis in agaricomycetes.

Trans-nuclei CRISPR/Cas9: safe approach for genome editing in the edible mushroom excluding foreign DNA sequences

Clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9)-assisted genome editing has been applied to several major edible agaricomycetes, enabling efficient gene targeting. This method is promising for rapid and efficient breeding to isolate high-value cultivars and overcome cultivation challenges. However, the integration of foreign DNA fragments during this process raises concerns regarding genetically modified organisms (GMOs) and their regulatory restrictions. In this study, we developed a foreign-DNA-free genome editing method in Pleurotus ostreatus by transferring the Cas9/guide RNA (gRNA) complex between nuclei in the dikaryotic state. We isolated a donor monokaryotic P. ostreatus strain expressing Cas9 and gRNA targeting pyrG by introducing a recombinant plasmid, which exhibited uracil auxotrophy and 5-fluoroorotic acid (5-FOA) resistance. This strain was then crossed with a pyrG+ recipient monokaryon, resulting in dikaryotic strains exhibiting 5-FOA resistance after mycelial growth. When these strains were de-dikaryonized into monokaryons through protoplasting, we obtained monokaryotic isolates harboring the recipient nucleus with small indels at the pyrG target site. Importantly, these isolates were confirmed to be free of foreign DNA through genomic PCR, Southern blotting, and whole-genome resequencing analyses. This is the first report of an efficient genome editing protocol in agaricomycetes that ensures no integration of exogenous DNA. This approach is expected to be applicable to other fungi with a dikaryotic life cycle, opening new possibilities for molecular breeding without the concerns associated with GMOs. KEY POINTS: • Successful genome editing via CRISPR/Cas9 trans-nuclei manner in P. ostreatus. • Recipient monokaryons from gene-edited dikaryons showed no exogenous DNA sequences. • Efficient genome editing protocol for safer molecular breeding in mushroom fungus.

Discovery of the first lichenized fungus in the family Chaetothyriaceae (Ascomycota), Ceramothyrium ryukyuense sp. nov

Ceramothyrium ryukyuense (Chaetothyriaceae) is described as a new species from Okinawa, southern Japan. It is characterized by subglobose minute ascomata (up to 110 μm diam.) covered with a brown mycelial pellicle, small ellipsoid 1(–2)-septate ascospores (8.7–13.8 × 3.4–4.9 μm) within a small ascus (20–30 × 13–17 μm), and a lichenized thallus. This species resembles non-lichenized Brazilian species, C. paiveae and C. philodendri, in producing minute ascomata and 1–4 or 7 septate ascospores. However, besides its lichenized status, C. ryukyuense is distinguished by its smaller asci (up to 30 μm long in C. ryukyuense vs. 30–42 μm long in C. paiveae, and 50–100 μm long in C. philodendri), and predominantly 1-septate ascospores in C. ryukyuense, whereas multi-septate in C. paiveae and C. philodendri. It was collected on a living leaf of Arecaceae in the subtropical forest near the seashore. In a phylogenetic tree based on nuITS and nuLSU sequences, C. ryukyuense formed a sister clade to Ceramothyrium exiguum which is known as an anamorphic species. DNA sequences of C. paiveae and C. philodendri, morphologically similar species to C. ryukyuense, were not available in this study. Algal cells distant from the perithecium exhibited continuous branching, while those near the perithecium were strongly deformed into a spherical shape and were partially unicellular. The photobiont of C. ryukyuense is suggested to be a species of Trentepohliales, inferred from a phylogenetic analysis based on the rbcl sequence. Ceramothyrium ryukyuense is the first report of a lichenized lineage within Chaetothyriaceae.

Putative APSES family transcription factor mbp1 plays an essential role in regulating cell wall synthesis in the agaricomycete Pleurotus ostreatus

The clade A APSES family transcription factors (Mbp1, Swi4, and Swi6) contribute to cell wall synthesis regulation in fungi. Herein, evolutionary relationships among these proteins were clarified by phylogenetic analysis using various ascomycetes and basidiomycetes, and then the detailed function of Mbp1 in cell wall synthesis regulation was analyzed in Pleurotus ostreatus. Our phylogenetic analysis revealed that Mbp1 and Swi6 are widely conserved among various fungi, whereas Swi4 is a protein specific for Saccharomycotina. In P. ostreatus, two putative clade A APSES family transcription factors, protein ID 83192 and 134090, were found and identified as Mbp1 and Swi6, respectively. The mbp1 gene was then disrupted through homologous recombination using P. ostreatus 20b strain (Δku80) as a host to obtain mbp1 disruption strains (Δmbp1). Disruption of mbp1 significantly decreased the growth rate and shortened aerial hyphae, suggesting that Mbp1 is involved in mycelial growth, especially aerial hyphal growth. Furthermore, thinner cell walls, decreased relative percentage of β-glucan, and downregulation of all β-glucan synthase genes were observed in Δmbp1 strains. Therefore, Mbp1 plays an essential role in β-glucan synthesis regulation in P. ostreatus. Disruption of mbp1 also impacted the expression profiles of chitin synthase genes, septum formation, and sensitivity to a chitin synthesis inhibitor, suggesting that Mbp1 also regulates chitin synthesis. In conclusion, Mbp1 is responsible for normal mycelial growth and regulates β-glucan and chitin synthesis in P. ostreatus. To the best of our knowledge, this is the first report on the detailed function of Mbp1 in cell wall synthesis regulation in fungi.

Morphological characterization, molecular identification, and metabolic profiles of two novel isolated bamboo mushrooms (Phallus sp.) from Thailand

The well-characterized edible and medicinal bamboo mushroom is Phallus indusiatus, a Chinese bamboo mushroom with long white indusium (skirt). To date, scientists have found more than five species of bamboo mushrooms in Thailand, containing bamboo mushrooms with long white, short white, and several colored skirts. Still, most of them are unidentified species and lack metabolic profile data. Hence, this study aims to evaluate the species of the long white-skirt Chinese bamboo mushroom-like (CH-isolate) and short white-skirt (TH-isolate) bamboo mushrooms isolated from a local farm in northern Thailand. External morphology and molecular identification were used to identify the species. Nutritional and metabolic studies were conducted to determine the nutrients and metabolites from both isolates. Our morphological and evolutionary phylogenetic analyses suggested that CH- and TH-isolates were different species. Interestingly, the CH-isolate, which has a similar morphology to P. indusiatus, clearly demonstrated the difference in species. In addition, the nutritional and metabolomic analysis revealed that CH- and TH-isolate contain different nutritional constituents and metabolic profiles. Our study reports the two new species of bamboo mushrooms that were suspected to be found in Thailand and their metabolic profiles that could be beneficially used in further studies. However, definitive confirmation of the novel species will be made in the future.

Environment-Mediated Vertical Transmission Fostered Uncoupled Phylogenetic Relationships between Longicorn Beetles and Their Symbionts

The Coleoptera Cerambycidae (longicorn beetles) use wood under different states (living healthy, freshly snapped, completely rot, etc.) in a species-specific manner for their larval diet. Larvae of some Cerambycidae groups have mycetomes, accessory organs associated with the midgut that harbor fungal symbiont cells. The symbionts are thought to improve nutrient conditions; however, this has yet to be shown experimentally. To deduce the evolutionary history of this symbiosis, we investigated the characteristics of the mycetomes in the larvae of longicorn beetles collected in Japan. Lepturinae, Necydalinae, and Spondylidinae are the only groups that possess mycetomes, and these three groups' mycetomes and corresponding fungal cells exhibit different characteristics between the groups. However, the phylogenetic relationship of symbiont yeasts does not coincide with that of the corresponding longicorn beetle species, suggesting they have not co-speciated. The imperfect vertical transmission of symbiont yeasts from female to offspring is a mechanism that could accommodate the host-symbiont phylogenetic incongruence. Some Lepturinae species secondarily lost mycetomes. The loss is associated with their diet choice, suggesting that different conditions between feeding habits could have allowed species to discard this organ. We found that symbiont fungi encapsulated in the mycetomes are dispensable for larval growth if sufficient nutrients are given, suggesting that the role of symbiotic fungi could be compensated by the food larvae take. Aegosoma sinicum is a longicorn beetle classified to the subfamily Prioninae, which does not possess mycetomes. However, this species contains a restricted selection of yeast species in the larval gut, suggesting that the symbiosis between longicorn beetles and yeasts emerged before acquiring the mycetomes.

Orchid Mycorrhizal Association of Cultivated Dendrobium Hybrid and Their Role in Seed Germination and Seedling Growth

Orchids are crucial for the horticulture industry. Mycorrhizal fungi benefit crops by improving nutrition, plant growth, and disease resistance. However, the mycorrhizal association of horticultural hybrid orchids is poorly understood. To address this, we investigated mycorrhizal colonization in the entire root system and assessed the mycorrhizal community using a Dendrobium cultivar, D. Stardust 'Firebird', obtained from three nurseries. Additionally, we isolated and tested mycorrhizal fungi in symbiotic culture to assess their role in the seed germination and growth of Dendrobium species. All plants were colonized by mycorrhizal fungi, with a higher colonization rate in mature than in juvenile plants. Molecular identification of mycorrhizal fungi by Sanger and high-throughput sequencing revealed that the cultivar was associated with a phylogenetically diverse group of fungi, including mycorrhizal fungi from Tulasnellaceae, and several wood-decaying fungi. The Tulasnellaceae isolates significantly enhanced the seed germination of three Dendrobium species and increased the survival rate and growth of asymbiotic seedlings of D. moniliforme. This study is the first comprehensive examination of mycorrhizal associations in horticultural orchid hybrids, providing valuable insights for commercial production.

Functional analysis of basidiomycete specific chitin synthase genes in the agaricomycete fungus Pleurotus ostreatus

Chitin is an essential structural component of fungal cell walls composed of transmembrane proteins called chitin synthases (CHSs), which have a large range of reported effects in ascomycetes; however, are poorly understood in agaricomycetes. In this study, evolutionary and molecular genetic analyses of chs genes were conducted using genomic information from nine ascomycete and six basidiomycete species. The results support the existence of seven previously classified chs clades and the discovery of three novel basidiomycete-specific clades (BI-BIII). The agaricomycete fungus Pleurotus ostreatus was observed to have nine putative chs genes, four of which were basidiomycete-specific. Three of these basidiomycete specific genes were disrupted in the P. ostreatus 20b strain (ku80 disruptant) through homologous recombination and transformants were obtained (Δchsb2, Δchsb3, and Δchsb4). Despite numerous transformations Δchsb1 was unobtainable, suggesting disruption of this gene causes a crucial negative effect in P. ostreatus. Disruption of these chsb2-4 genes caused sparser mycelia with rougher surfaces and shorter aerial hyphae. They also caused increased sensitivity to cell wall and membrane stress, thinner cell walls, and overexpression of other chitin and glucan synthases. These genes have distinct roles in the structural formation of aerial hyphae and cell walls, which are important for understanding basidiomycete evolution in filamentous fungi.

Two new Mycena section Calodontes species: One newly discovered and the other new to Japan

In 2017, two candidate species of Mycena were reported from Japan, with the Japanese names "Togari-sakura-take" and "Mitsuhida-sakura-take". However, to date, no taxonomic study or formal description has been undertaken for these two species. In the present study, we conducted comprehensive morphological and molecular phylogenetic examinations of "Togari-sakura-take" and "Mitsuhida-sakura-take", and compared them to known species within the genus Mycena. We performed phylogenetic analyses on a concatenated dataset, including the internal transcribed spacer region of ribosomal RNA, RNA polymerase II largest subunit, and translation elongation factor-1 alpha genes. "Togari-sakura-take" formed a clade with Mycena subulata, which was recently described from China, whereas "Mitsuhida-sakura-take" formed a distinct independent clade. We identified the former as M. subulata based on molecular phylogenetic analyses and morphological observations. However, the Japanese specimens displayed dextrinoid cheilocystidia and caulocystidia as well as the inamyloidity of basidiospores, which differed from the original description of M. subulata based on the materials from China. "Mitsuhida-sakura-take" was characterized by its remarkably dense lamellae and could be distinguished from known Mycena species by the combination of absent pleurocystidia and presence of bowling pin-shaped cheilocystidia. Here, we describe "Mitsuhida-sakura-take" as a new species, named Mycena densilamellata, in the section Calodontes.

Disruption of the pkac2 gene in Pleurotus ostreatus alters cell wall structures and enables mycelial dispersion in liquid culture

In this study, we developed a mycelial dispersion strain by disrupting the pkac2 gene in the white-rot fungus Pleurotus ostreatus. pkac2 is a catalytic subunit gene of protein kinase A, which regulates several transcription factors related to cell wall synthesis. Liquid cultures of the Δpkac2 strains showed very high mycelial dispersibility and were visibly different from the wild-type (WT) strain. Although growth on agar medium was slower than that of WT, Δpkac2 strains grew faster in liquid culture and had approximately twice the mycelial dry weight of WT after 5 days of culture. Microscopic observations showed that the cell walls of the Δpkac2 strains were thinner compared to WT. The β-glucan content in the cell walls decreased in the pkac2 disruptants, although the transcription levels of β-glucan synthase genes increased. Furthermore, the Δpkac2 strains showed decreased hydrophobicity and stress tolerance compared to WT. These results indicate that disruption of the pkac2 gene in P. ostreatus alters the structure of the cell wall surface layer, resulting in high-density cultures due to mycelial dispersion.

Taxonomic and life cycle reappraisals of the marine basidiomycete Nia vibrissa complex, with descriptions of three new Nia species

The marine basidiomycete Nia vibrissa has been regarded as a species complex, possibly including several species, because morphological variations in fruitbody, spore, and spore appendage have been observed in materials from worldwide collections. Using more than 50 monosporic isolates of N. vibrissa-like fungi mainly obtained from Japanese beach coasts, we investigated their molecular phylogeny, morphological characteristics, mating compatibility, nuclear behavior during spore formation, and life cycles. Molecular phylogenetic analyses separated the examined strains into seven clades. Each clade of fungi exhibited distinctive characteristics in fruitbodies and spores produced by culturing monokaryotic strains and mated dikaryotic strains; these characteristics included the color of fruitbodies, apical structure of peridial hair hyphae, spore shape, and apical structure of spore appendages. Mating tests of monokaryotic strains demonstrated mating compatibility between strains within a clade and incompatibility among clades. Therefore, each clade of fungi was phylogenetically, morphologically, and biologically recognized as a different Nia species. Observation of the type specimen of N. vibrissa revealed a tiny T-shaped apical structure of spore appendages-not mentioned in the original description-that is unique to the species. This finding, together with the original description, suggests that our studied strains include N. aff. vibrissa, whose morphology is mostly identical to N. vibrissa sensu stricto, and three new species. Thus, we describe three new Nia species and propose emendation of the descriptions of the genus Nia. Culture-based studies have demonstrated that Nia species have both sexual and asexual morphs that produce morphologically similar fruitbodies (basidiomata and conidiomata) and spores (basidiospores and conidia). Because it has both morphs forming appendaged waterborne basidiospores and conidia, Nia must be the most well-adapted marine basidiomycete, ensuring the continuation of new generations by two morphs, while distributing in and inhabiting numerous marine environments.

Mycorrhizal specificity differences in epiphytic habitat: three epiphytic orchids harbor distinct ecological and physiological specificity

Orchidaceae has diversified in tree canopies and accounts for 68% of vascular epiphytes. Differences in mycorrhizal communities among epiphytic orchids can reduce species competition for mycorrhizal fungi and contribute to niche partitioning, which may be a crucial driver of the unusual species diversification among orchids. Mycorrhizal specificity-the range of fungi allowing mycorrhizal partnerships-was evaluated by assessment of mycorrhizal communities in the field (ecological specificity) and symbiotic cultures in the laboratory (physiological specificity) for three epiphytic orchids inhabiting Japan. Mycorrhizal communities were assessed with co-existing individuals growing within 10 cm of each other, revealing that ecological specificity varied widely among the three species, ranging from dominance by a single Ceratobasidiaceae fungus to diverse mycobionts across the Ceratobasidiaceae and Tulasnellaceae. In vitro seed germination tests revealed clear differences in physiological specificity among the three orchids, and that the primary mycorrhizal partners contributed to seed germination. In vitro compatibility ranges of three orchids strongly reflect the mycorrhizal community composition of wild populations. This suggests that differences in in situ mycorrhizal communities are not strongly driven by environmental factors, but are primarily due to physiological differences among orchid species. This study shows that the symbiotic strategy among the epiphytic orchid species varies from specialized to generalized association, which may contribute to biotic niche partitioning.

Fungi associated with woody tissues of Acer pseudoplatanus in forest stands with different health status concerning sooty bark disease (Cryptostroma corticale)

From 2018 to 2020, Germany experienced periods of exceptional weather conditions. Extremely high summer temperatures and precipitation deficits induced stress and mortality in forest trees. Acer pseudoplatanus (sycamore) was one of the affected tree species. Symptoms of sooty bark disease (SBD) and severe damage of entire stands, both caused by the fungal species Cryptostroma corticale, were reported more frequently. To explore the non-symptomatic distribution of C. corticale, wood cores from visibly healthy sycamore stems were sampled and all outgrowing fungi were identified and recorded. In total, 50 trees, aged 30–65 years, were sampled at five different forest stands, from which 91 endophytic filamentous morphotypes could be isolated. The fungal endophytic community in the woody tissue of the sycamore trees varied greatly at the different sites and between the trees. The number of isolated morphotypes at the different sites ranged from 13 to 44 and no morphotype was found at all sites. At 1.20-m stem height, 3.3 fungi could be isolated from woody tissue per tree on average. The most abundant species isolated from visibly healthy sycamore in regard to both occurrence at the studied sites and continuity was C. corticale. It was recorded at four of the studied forest stands, from 26% of all studied sycamore trees, and had a frequency of 7.85% relative to the 293 isolated filamentous strains that were isolated. The second most abundant species was Xylaria longipes followed by Lopadostoma turgidum. In this study clear evidence for the endophytic lifestyle of C. corticale is presented which thus appears to be spread further than expected based on visible SBD symptoms.

Symbiotic Culture of Three Closely Related Dendrobium Species Reveals a Growth Bottleneck and Differences in Mycorrhizal Specificity at Early Developmental Stages

Mycorrhizal specificity, i.e., the range of fungi allowing mycorrhizal partnerships, differs among orchid species, but that at early developmental stages is unclear. We investigated whether mycorrhizal specificity during seed germination and seedling development differs among three Dendrobium species, D. officinale, D. okinawense and D. moniliforme, in vitro. Nine mycorrhizal fungal strains were obtained from the roots of these species and cultured with a seed of each Dendrobium species. Five to eight fungal strains stimulated seed germination, whereas one to four fungal isolates significantly promoted protocorm development in the three species. To evaluate effects on leafy seedling growth, seedlings obtained from asymbiotic culture were cultured with nine fungal isolates. D. officinale and D. okinawense showed specificity for a single Serendipitaceae or Tulasnellaceae isolate, whereas D. moniliforme exhibited specificity for three isolates of Serendipitaceae and Tulasnellaceae. Therefore, the three Dendrobium species had a growth bottleneck from seed germination to the protocorm stage, and mycorrhizal specificity of protocorm growth and seedling development in vitro varied among the species. Our findings imply divergent mycorrhizal specificity in Dendrobium species at early developmental stages. This study provides insights into the diversity of orchid mycorrhizal specificity, as well as valuable information for conservation of endangered orchids.

Impact of climate change on wood and woodworkers-Cryptostroma corticale (sooty bark disease): A risk factor for trees and exposed employees

Climate changes have promoted an increased fungal infection of maple trees with Cryptostroma corticale, the causative agent of sooty bark disease. The hosts of C. corticale are maples, and since the early 2000s the fungus has been appearing more frequently in European forests, due to the droughts and hot summers of recent years. Infestation by C. corticale discolors the wood and makes it unusable for further processing, which leads to considerable economic damage in the timber industry. Therefore, the occurrence and spread of sooty bark disease raise serious problems. In addition to forestry and economic problems, the conidiospores of C. corticale can also cause health problems in exposed wood workers and they can trigger hypersensitivity pneumonitis (HP). Since the spores, which are deposited over the entire area under the bark of infected trees, can spread during processing, exposed workers must take special precautions to protect themselves against exposure. If an occupational disease is nevertheless suspected following exposure to C. corticale, valid diagnostics are required to confirm possible HP and derive appropriate therapies and exposure reduction or avoidance. Diagnosis of HP is based on several criteria, one of them is the detection of specific IgG in patient's serum against the potentially triggering antigens, in this case C. corticale antigens. To produce a diagnostic tool to measure C. corticale specific IgG, which is not commercially available so far, spores and mycelial material from ITS-sequenced strains of C. corticale was prepared and analyzed. These biochemically characterized extracts of spore and mycelial antigens were biotinylated and coupled to Streptavidin-ImmunoCAPs. To validate these diagnostic test tools the first step is to measure the concentration of C. corticale specific IgG in sera of healthy non-exposed and healthy exposed subjects to establish cut-off values. Suitable participants were recruited and the individual exposure to C. corticale and symptoms experienced during or after working with infected maple trees were recorded using questionnaires. Finally, diagnostic tools for serological testing in suspected cases of HP by C. corticale were created and evaluated. The following article provides recommendations for the treatment and disposal of infected damaged wood and for occupational health protection procedures. Secondly, the diagnosis of HP induced by exposure to C. corticale as an occupational disease is described including the verification of newly developed serological test tools for antigens of C. corticale.

Dominant Dendrobium officinale mycorrhizal partners vary among habitats and strongly induce seed germination in vitro

Dendrobium officinale (Orchidaceae) is an endangered epiphytic orchid that has been well studied as a medicinal plant. Although previous studies have shown that various fungal isolates promote D. officinale seed germination and seedling development in vitro, mycorrhizal associations among its wild populations remain poorly understood. In this study, we identified mycorrhizal fungi associated with D. officinale (36 individuals from six sites) using Sanger sequencing and compared fungal communities among sites and habitats (lithophytic vs. epiphytic individuals). Among the obtained sequences, 76 belonged to orchid mycorrhizal fungi (OMF), among which Tulasnellaceae accounted for 45.8% and Serendipitaceae for 28.1%. The Serendipitaceae operational taxonomic unit (OTU) SE1 was the most dominant partner, accounting for 27.1% of all detected fungal sequences, followed by a Tulasnellaceae OTU, TU27, which accounted for 15.6%. The relative frequencies of Serendipitaceae and Tulasnellaceae differed greatly between lithophytic and epiphytic individuals. Serendipitaceae accounted for 47.3% of the OMF sequences among lithophytes, and Tulasnellaceae for 95.2% among epiphytes. Mycorrhizal community composition also varied among sites. We further conducted in vitro symbiotic culture from seeds with six fungal isolates. Two Serendipitaceae and two Tulasnellaceae isolates, including SE1 and TU27, significantly promoted seed germination and seedling development. These results indicate that D. officinale is mainly associated with Tulasnellaceae and Serendipitaceae as its main fungal partners, which strongly induced seed germination and seedling development in vitro, suggesting their association with D. officinale through its life cycle.

The Lichen Photobiont Genus Rhizonema (cyanobacteria) Exhibits Diverse Modes of Branching, Both False and True

The recently described genus Rhizonema is among the most important cyanobacterial partners in lichen symbioses, but its morphological characterization in the genus diagnosis-true branching of the T-type-appears at odds with several published figures showing false branching. We investigated cyanobiont branching and cell division with light microscopy in two basidiolichens from Florida and one from Japan, including aposymbiotically cultured material of the latter. Mycobiont species identities (Cyphellostereum jamesianum, Dictyonema darwinianum, and D. moorei) and photobiont genus identity (Rhizonema) were corroborated with ITS and rbcLX sequences, respectively. Single and paired false branching occurred commonly in all three strains examined. False branches developed adjacent to necridic cells or heterocytes, or by separation of vegetative cells at compression folds in the trichome. Non-transverse cell divisions, usually oblique, were observed in two of the three Rhizonema strains examined. T-type true branches sometimes arose from such divisions, although oblique growth from the branch cell often resulted in ambiguous branch junctions. Additionally, Y-type true branches appeared to grow from contorted filaments. In cultured material, a kind of pseudo-branch sometimes arose from single- or several-celled segments liberated from trichome apices. The segments attached secondarily to filaments and grew there as apparent branches. We conclude that Rhizonema is a genus of considerable morphological flexibility, with multiple modes of branching possible in a single strain. While true branching or non-transverse divisions, when observable, may help distinguish Rhizonema from the phenotypically similar Scytonema, false branching occurs commonly in both genera, and therefore cannot be used to distinguish them.

Diplodia tip blight pathogen's virulence empowered through host switch

Increased drought combined with emerging pathogens poses an increased threat to forest health. This is attributable to the unpredictable behaviour of forest pathosystems, which can favour fungal pathogens over the host under persistent drought stress conditions. Diplodia sapinea (≡ Sphaeropsis sapinea) is one of the most severe pathogens in Scots pine (Pinus sylvestris) causing Diplodia tip blight (conifer blight) under certain environmental conditions. Recently, the fungus has also been isolated from non-conifer hosts, indicating that it has a broader host range than previously known. In this study we compared the impact of different levels of water availability on necrosis length caused by D. sapinea strains isolated as endophytes (eight strains isolated from asymptomatic Scots pine) and pathogens (five strains isolated from symptomatic Scots pine) and five strains isolated from symptomatic non-pine hosts. For all strains the decreased water availability increased the necrosis length in Scots pine shoots. The isolates from non-pine hosts caused the most severe reactions under all water availabilities. The results of the study indicate the likelihood that effects of climatic changes such as drought will drive D. sapinea damage in Scots pine-dominated forests and increase mortality rates in affected trees. Further, the higher necrosis in the Scots pines caused by strains that had performed a host switch are concerning with regard to future scenarios thus increasing infection pressure on Scots pine from unknown sources.

A Non-Destructive High-Speed Procedure to Obtain DNA Barcodes from Soft-Bodied Insect Samples with a Focus on the Dipteran Section of Schizophora

While the need for biodiversity research is growing, paradoxically, global taxonomical expertise is decreasing as a result of the neglected funding for young academics in taxonomy. Non-destructive approaches for DNA barcoding are necessary for a more efficient use of this dwindling expertise to fill gaps, and identify incorrect entries in sequence databases like BOLD or GenBank. They are efficient because morphological re-examination of species vouchers is still possible post-DNA barcoding. Non-destructive approaches for Diptera with a comprehensive species representation or the consideration of diagnostic fragile morphological characters are missing. Additionally, most non-destructive approaches combine a time intensive and non-destructive digestion step with common DNA extraction methods, such as commercial kits or CTAB DNA isolation. We circumvented those approaches and combined a modified non-destructive TE buffer high-speed DNA extraction, with a PCR inhibitor-resistant PCR reaction system, to a non-destructive DNA barcoding procedure for fresh and frozen samples of the Schizophora (Diptera). This method avoids morphological impairment and the application of harmful chemicals, is cost and time effective, restricts the need for laboratory equipment to a minimum, and prevents cross-contamination risk during DNA isolation. Moreover, the study indicates that the presented non-destructive DNA barcoding procedure is transferable to other soft-bodied insects. We suggest that PCR inhibitor-resistant master mixes enable the development of new—and the modification of existing—non-destructive approaches with the avoidance of further DNA template cleaning.

Host Specificity and Seasonal Variation in the Colonization of Tubakia sensu lato Associated with Evergreen Oak Species in Eastern Japan

Foliar fungal endophytes are ubiquitous and hyperdiverse, and tend to be host-specific among dominant forest tree species. The fungal genus Tubakia sensu lato is comprised of foliar pathogens and endophytes that exhibit host preference for Quercus and other Fagaceae species. To clarify interspecific differences in ecological characteristics among Tubakia species, we examined the endophyte communities of seven evergreen Quercus spp. at three sites in eastern Japan during summer and winter. Host tree species was the most significant factor affecting endophyte community composition. Tubakia species found at the study sites were divided into five specialists and three generalists according to their relative abundance in each host species and their host ranges. Specialists were dominant on their own host in summer, and their abundance declined in winter. To test the hypothesis that generalists are more widely adapted to their environment than specialists, we compared their spore germination rates at different temperatures. Spores of generalist Tubakia species were more tolerant of colder temperatures than were spores of specialist Tubakia species, supporting our hypothesis. Seasonal and site variations among Tubakia species were also consistent with our hypothesis. Host identity and ecology were significantly associated with endophyte community structure.

Mitospore formation on pure cultures of Tuber japonicum (Tuberaceae, Pezizales) in vitro

The members of the genus Tuber are Ascomycota that form ectomycorrhizal associations with various coniferous and broadleaf tree species. In the teleomorphic stage, the species of the genus produce fruit bodies known as true truffles. Recent studies have discovered mitosporic structures, including spore mats, of several Tuber species on forest soils, indicating the presence of a cryptic anamorphic stage or an unknown reproductive strategy. Here, we report in vitro mitospore formation on the mycelium of T. japonicum, which belongs to the Japonicum clade, collected in several regions in Japan. Twenty of the 25 strains formed mitospores on modified Melin-Norkrans agar medium, indicating that mitospore formation is likely a common trait among strains of T. japonicum. The fungus forms repeatedly branched conidiophores on aerial hyphae on colonies and generates holoblastic mitospores sympodially on the terminal and near apical parts and/or occasionally on the middle and basal parts of the conidiogenous cells. Mitospores are hyaline and elliptical, obovate, oblong, or occasionally bacilliform, with a vacuole and often distinct hilar appendices. Formation of mitospores by T. japonicum in vitro is useful in understanding the functions of mitospores in the genus Tuber under controlled environmental conditions.

Meiotic Silencing in Dothideomycetous Bipolaris maydis

The filamentous ascomycete Bipolaris maydis is a plant pathogen that causes corn leaf blight and has been used in cytological studies of sexual reproduction. In this fungus, when null mutants of each septin are crossed with the wild-type strain, all ascospores derived from the same asci show abnormal morphology. The phenomenon was remarkably similar to the event known as "ascus dominance" in Neurospora crassa, which is known to be caused by MSUD (meiotic silencing by unpaired DNA). However, it is not clear whether B. maydis possesses functional MSUD. The object of this study is to elucidate whether this fungus carries a functional MSUD system that causes ascus dominance in the crosses of septin mutants and the wild-type strain. The results of homozygous and heterozygous crossing tests with mutants, having the insertional CDC10-septin gene sequence into the genome, suggested that the ascus dominance in B. maydis is triggered by the unpaired DNA as in N. crassa. To investigate whether MSUD is caused by the same mechanism as in N. crassa, an RNA-dependent RNA polymerase, one of the essential factors in MSUD, was identified and disrupted (Δrdr1) in B. maydis. When the Δrdr1 strain was crossed with each mutant of the septins, ascus dominance did not occur in all crosses. These results suggest that this ascus dominance is caused by RNA silencing triggered by an unpaired gene, as in N. crassa, and septin genes were affected by this silencing. To date, although MSUD has been found only in Fusarium graminearum and N. crassa, which are classified as Sordariomycetes, this study showed that MSUD is also functional in B. maydis, which is classified as a Dothideomycete. These results showed the possibility that this posttranscriptional regulation is extensively conserved among filamentous ascomycetes.

Two new species of <i>Sistotrema</i> s.l. (<i>Cantharellales</i>) from Japan with descriptions of their ectomycorrhizae

We describe two new species of resupinate Sistotrema sensu lato (Cantharellales) collected in Japan: S. flavorhizomorphae and S. chloroporum. Both species have urniform basidia with more than four sterigmata and monomitic hyphal system, oil-rich hyphae in subiculum, which is typical for this genus. Sistotrema chloroporum is characterized by poroid hymenophore partly yellowish-green, basidia 4-6-spored, medium-sized basidiospores (4.5-6.5 × 3.5-6 µm), and broadleaf forest habitat. Sistotrema flavorhizomorphae is characterized by hydnoid-irpicoid hymenophore, bright yellowish rhizomorphs, basidia 6-8-spored, small basidiospores (3-3.5 × 2.5-3 µm), and pine forest habitat. Phylogenetic trees inferred from the fungal nrDNA ITS and LSU and the rpb2 sequences supported that both species were distinct and grouped with other ectomycorrhizal Sistotrema and Hydnum species, but their generic boundary was unclear. Mycorrhizae underneath basidiomes of both species were identified and described via molecular techniques. Mycorrhizae of S. chloroporum have similar characteristics to those of other Sistotrema s.l. and Hydnum species, i.e., S. confluens and H. repandum, whereas S. flavorhizomorphae has a distinct morpho-anatomy, for example, a distinct pseudoparenchymatous mantle. Comprehensive characterizations of basidiomes and mycorrhizae improve the taxonomic analysis of mycorrhizal species of Sistotrema s.l.

<i>In-vitro</i> symbiotic germination of seeds of five mycoheterotrophic <i>Gastrodia</i> orchids with <i>Mycena</i> and <i>Marasmiaceae</i> fungi

We performed in-vitro germination tests on seeds from five Gastrodia orchids (G. confusa, G. elata var. elata, G. elata var. pallens, G. nipponica, and G. pubilabiata) using one Marasmiaceae and two Mycena isolates. Mycena sp. 1 promoted germination of all five Gastrodia orchids, with root and/or tuber formation observed in G. confusa, G. nipponica, and G. pubilabiata. No additional growth was observed in the other two orchids. Mycena sp. 2 induced G. confusa, G. elata var. elata, and G. nipponica germination, whereas Marasmiaceae sp. 1 induced G. nipponica and G. pubilabiata germination. Phylogenetic analyses indicated that the two Mycena isolates represent distinct lineages within the Mycenaceae. Mycena sp. 1 and Marasmiaceae sp. 1 are closely related to Mycena abramsii and Marasmiellus rhizomorphogenus, respectively. Our results imply that Mycena and marasmioid fungi play important roles in early development in Gastrodia species, and that Mycena fungi in particular may be common mycobionts of Gastrodia species. Root and/or tuber development was observed with four plant-fungus combinations, implying that these associations persist throughout the life cycle, whereas G. elata var. elata may require different associates over time. Our findings will contribute to elucidating the mycorrhizal associations of mycoheterotrophic orchids throughout their life cycle.

Neotypification of Claviceps humidiphila and recognition of C. bavariensis sp. nov

Claviceps humidiphila [≡ C. purpurea var. phalaridis] was previously typified with the holotype collected by Tanda in Japan and an epitype from Bavaria, Germany. Phylogenetic analyses based on translation elongation factor 1-α (TEF1-α) and RNA polymerase II second largest subunit (RPB2) indicated that the previously designated epitype from Germany was not conspecific with the Japanese species. The German specimen is proposed as a new species, C. bavariensis, and a specimen collected from the type location (Chiba, Japan) is designated as a neotype for C. humidiphila, replacing the lost holotype.

Systematic revision of Hydnum species in Japan

Hydnum (Hydnaceae, Basidiomycota) exhibits endemic species diversity in East Asia; however, few comprehensive systematic studies have been conducted to date. Here, we performed morphological, ecological, phylogenetic, and biological evaluations of the taxonomy of Hydnum species in Japan. In total, 186 Japanese Hydnum specimens were used for morphological observations. Phylogenetic trees were constructed using sequence data of nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS) region and a portion of translation elongation factor 1-α (tef1). Intra- and interspecific mating tests using 78 monokaryotic strains of 13 species did not conflict with species delimitation inferred from their ITS and tef1 phylogenetic relationships. This study provides detailed morphological descriptions of 15 rigorously identified species from Japan, nine of which are described as new: H. alboluteum, H. albopallidum, H. pinicola, H. itachiharitake, H. minospororufescens, H. orientalbidum, H. subberkeleyanum, H. tomaense, and H. tottoriense. Three species documented in this work are new to Japan: H. boreorepandum, H. mulsicolor, and H. umbilicatum. The remaining three species (H. cremeoalbum, H. minus, and H. repando-orientale), previously reported from Japan, are redescribed using data from newly collected materials. We also transferred two old species (Hericium fimbrillatum and Sarcodon nauseofoetidus) from East Asian Hydnum into other genera.

Clavaria cystidiata sp. nov. from India

A new species, Clavaria cystidiata, was collected and described from Kerala State, India. The species is proposed as new based on morphological and molecular evidence. Clavaria cystidiata differs from other closely related Clavaria species by its garlic smell, yellowish basidiomata, clamp connections at the base of basidia, and by the prominent presence of versiform cystidia. Sequence analyses of the nuclear rDNA internal transcribed spacer (ITS) region supports phylogenetic separation of C. cystidiata within Clavariaceae.

Comparative study of DNA extraction methods for identification of medicinal mushrooms

The isolation of high quantity and intact DNA is of a great significance for molecular identification of higher fungi. The aim of this study was to compare two DNA extraction methods for isolation of DNA from medicinal mushrooms of Agaricomycetes class. A modified CTAB method and a modified SDS method were compared by the yield and purity of the extracted DNA, its fragmentation state and suitability for amplification. The results demonstrated high efficiency of both methods in regard to DNA yield (14.18 -144.28 ng DNA/mg biomass with CTAB method and 15.03 -108.34 ng DNA/mg biomass with SDS method). The CTAB method provided DNA extracts with higher purity (A260/A280 ranged from 1.83 to 1.99) in comparison with the SDS method (A260/A280 = 1.53 -1.86). The modified CTAB method produced amplifiable DNA from all mushroom isolates, while the SDS method demonstrated suitability for amplification only in 50% of the samples. Therefore, the modified CTAB method could be the method of choice for DNA extraction from medicinal mushrooms. The analyzed isolates were subjected to molecular identification by ITS1-5.8S-ITS2 rRNA gene sequence analysis and were identified as Ganoderma resinaceum, Trametes versicolor, Fomitopsis pinicola and Inonotus hispidus.

Strong primer bias for Tulasnellaceae fungi in metabarcoding: Specific primers improve the characterization of the mycorrhizal communities of epiphytic orchids

Primer bias toward Tulasnellaceae fungi during PCR is a known issue with metabarcoding analyses for the assessment of orchid mycorrhizal communities. However, this bias had not been evaluated for the fungal communities of epiphytic orchids, which account for 69% of all orchid species diversity. We compared the mycorrhizal communities detected using two primer pairs, a fungal universal primer pair (ITS86F/ITS4) and Tulasnella-specific primer pair (5.8STulngs/ITS4-Tul2), using a mock community of fungal isolates from epiphytic orchids and also environmental samples, including orchid roots and a tree bark tip from the host tree of an epiphytic orchid collected. The detected mycorrhizal communities differed widely depending on the primer pairs used. The fungal universal primer pair successfully identified Ceratobasidiaceae and Serendipitaceae fungi but did not reflect Tulasnellaceae diversity. Tulasnellaceae fungi were mainly detected using the Tulasnella-specific primer pair. These tendencies were observed in both the mock community and environmental samples. These results strongly suggest that the use of a Tulasnella-specific primer in combination with a fungal universal primer is essential for assessing the mycorrhizal communities of orchids through metabarcoding analysis, especially in epiphytic orchids. Our study contributes to further understanding of the diversity of mycorrhizal fungi in orchids.

An exocyst component, Sec5, is essential for ascospore formation in Bipolaris maydis

In this study, we identified Sec5 in Bipolaris maydis, a homologue of Sec5 in Saccharomyces cerevisiae and a possible exocyst component of the fungus. To examine how Sec5 affects the life cycle of B. maydis, we generated null mutant strains of the gene (Δsec5). The Δsec5 strains showed a strong reduction in hyphal growth and a slight reduction in pathogenicity. In sexual reproduction, they possessed the ability to develop pseudothecia. However, all ascospores were aborted in any of the asci obtained from crosses between Δsec5 and the wild-type. Our cytological study revealed that the abortion was caused by impairments of the post-meiotic stages in ascospore development, where ascospore delimitation and young spore elongation occur.

Fungi Associated With Woody Tissues of European Beech and Their Impact on Tree Health

Filamentous fungi associated with woody tissues of European Beech (Fagus sylvatica) and isolated from diseased trees and healthy trees were examined in relation to their impact on tree health. To this end, classical culture-based isolation methods, in planta inoculations and fungal identification using ITS-barcode and morphological characters were used. Stem endophytes of healthy beech saplings collected in German forests were isolated to determine endophyte communities in woody stem tissues. Pathogenicity tests were performed on living potted beech saplings using twelve selected fungal pathogens and wood inhabiting fungi (Hypocreales, Botryosphaeriales, and Xylariales) originating mainly from European beech with symptoms of the complex disease Vitality loss, or from bark necroses, or known to be common endophytes of beech. The impact of these ascomycetous fungi with respect to tree health was discussed. The potential influences of endophytic fungi of beech and of test conditions are discussed in relation to the success of inoculation. All tested fungal strains except for Neonectria ditissima were able to establish themselves post inoculation in the beech stems and caused necroses when there was sufficient water, but at different severities. Under the experimental conditions, Botryosphaeria corticola was shown to be the most virulent tested latent pathogen against F. sylvatica. In the context of climate change and global warming, the tested Botryosphaeriaceae are able to play a primary role in the disease progress of Vitality loss of Beech. The key role of Neonectria coccinea in causing bark necroses and the loss of vitality in beech was confirmed because the tested strain induced large lesions on the beech saplings.

Digging Up the Roots: Taxonomic and Phylogenetic Disentanglements in Corticiaceae s.s. (Corticiales, Basidiomycota) and Evolution of Nutritional Modes

Corticiaceae is one of the traditional families of the Agaricomycetes and served for a long time as a convenient placement for basidiomycetes with a resupinate, corticioid form of fruiting body. Molecular studies have helped to assign many corticioid fungi to diverse families and orders; however, Corticiaceae still lacks a phylogenetic characterization and modern circumscription. Here, we provide the first comprehensive phylogenetic and taxonomic revision of the family Corticiaceae based on extensive type studies and sequences of nLSU, ITS, IGS, nSSU, and mtSSU regions. Our analyses support the recognition of ten monophyletic genera in the Corticiaceae, and show that nutritional mode is not a robust basis for generic delimitations in the family. The genus Mycobernardia and the species Corticium thailandicum, Erythricium vernum, and Marchandiomyces allantosporus are described as new to science, and five new combinations are proposed. Moreover, ancestral character state reconstruction revealed that saprotrophy is the plesiomorphic nutritional mode in the Corticiaceae, while several transitions have occurred to diverse nutritional modes in this family. Identification keys are provided to the genera in Corticiaceae s.s. as well as to the species in Corticium, Erythricium, Laetisaria, and Marchandiomyces.

Effects of Pesticides on the Diversity of Endophytic Fungi in Tea Plants

We examined the effects of agrochemicals on the endophytic fungal community associated with tea plants. Endophytic fungi were isolated from four different tea plant tissues (bark, xylem, old leaves, new leaves) collected from pesticide-treated and untreated plots. In pesticide-treated plot, the acaricides, fungicides, and insecticides are typically applied 3 times each year. The infection rate was slightly lower in the pesticide-treated plot, but the difference between plots was not statistically significant. Colletotrichum camelliae, Phyllosticta capitalensis, and Pleosporales sp. were common endophytes in both plots. Among a total of 41 fungal species, only 21 were considered common endophytes. Colletotrichum pseudomajus was the predominant endophyte in the bark tissue in the untreated plot, whereas C. camelliae was predominant in the pesticide-treated plot. Paraphaeosphaeria neglecta and Phoma bellendis were predominant in the xylem tissues of samples from the untreated and treated plots, respectively. Colletotrichum camelliae was the most commonly found species in leaf tissues in both plots, but the colonization frequency was significantly lower in the pesticide-treated plot. Species richness was not affected by pesticide treatment. The community structure of endophytic fungi in stem tissues (bark and xylem) differed significantly between plots, but leaf tissue endophytic fungal community structure was not significantly influenced by pesticide treatment.

Multilocus phylogenies reveal three new truffle-like taxa and the traces of interspecific hybridization in Octaviania (Boletaceae, Boletales)

Among many convergently evolved sequestrate fungal genera in Boletaceae (Boletales, Basidiomycota), the genus Octaviania is the most diverse. We recently collected many specimens of Octaviania subg. Octaviania, including several undescribed taxa, from Japan and the Americas. Here we describe two new species in subgenus Octaviania, O. tenuipes and O. tomentosa, from temperate to subtropical evergreen Fagaceae forests in Japan based on morphological observation and robust multilocus phylogenetic analyses (nrDNA ITS and partial large subunit [LSU], translation elongation factor 1-α gene [TEF1] and the largest subunit of RNA polymerase II gene [RPB1]). Based on specimens from the Americas as well as studies of the holotype, we also taxonomically re-evaluate O. asterosperma var. potteri. Our analysis suggests that O. asterosperma var. potteri is a distinct taxon within the subgenus Octaviania so we recognize this as O. potteri stat. nov. We unexpectedly collected O. potteri specimens from geographically widespread sites in the USA, Japan and Colombia. This is the first verified report of Octaviania from the South American continent. Our molecular analyses also revealed that the RPB1 sequence of one O. tenuipes specimen was identical to that of a closely related species, O. japonimontana, and that one O. potteri specimen from Minnesota had an RPB1 sequence of an unknown species of O. subg. Octaviania. Additionally, one O. japonimontana specimen had an unusually divergent TEF1 sequence. Gene-tree comparison and phylogenetic network analysis of the multilocus dataset suggest that these heterogenous sequences are most likely the result of previous inter- and intra-specific hybridization. We hypothesize that frequent hybridization events in Octaviania may have promoted the high genetic and species diversity found within the genus.

Revision of the genus Aciculosporium (Clavicipitaceae) with a description of a new species on wavyleaf basketgrass, and proline-containing cyclic dipeptide production by A. take

The genus Aciculosporium (Clavicipitaceae, Hypocreales, Ascomycota)was established in 1908 for A. take , which is the causal fungus of witches' broom of bamboo. Although the original description was valid at that time, a type specimen for A. take has not been designated. To standardize the use of this genus and species name, a neotypification and reference specimen of A. take are proposed. Multilocus phylogenetic analyses based on DNA sequences from 28S rDNA, TEF, Tub2, Mcm7, and RPB2 revealed that A.sasicola is from a different lineage to A. take, and other specimens from wavyleaf basket grass (Oplismenus undulatifolius) represent a distinct species proposed here as Aciculosporium oplismeni sp. nov. Chemical analysis using mass spectrometry and nuclear magnetic resonance spectroscopy showed that A. take produces four proline-containing cyclic dipeptides, which are moieties of ergot alkaloids. However, ergot alkaloids, lolines, peramine, indole-diterpenes, and lolitrem were not detected in the culture solvent. This study offers clarification of the lineage and morphology of this genus.

Antiproliferative and antibacterial activity of extracts of Ganoderma strains grown in vitro

In this bioprospecting study the biological activities of extracts of the in vitro culture of Ganoderma Mexican strains were evaluated. The extracts were tested by the Sulforhodamine B staining method for antiproliferative activity and the plate microdilution method for antibacterial activity. Extracts that proved bioactive in these two activities, the antioxidant activity (Galvinoxyl, ABTS, and DPPH) and total phenolic contents (Folin-Ciocalteu) were additionally determined, as well as acute toxicity (Artemia franciscana). In the antiproliferative activity Ganoderma curtisii strain (GH-16-015) obtained a remarkable value of GI50 ≤ 50 µg/mL against tumor lines: A549, HBL-100, HeLa, and T-47D. G. curtisii strains (GH-16-012 and GH-16-015) showed MIC values = 500 µg/mL against Staphylococcus aureus. G. curtisii strain (GH-16-012) almost reduced by 50% the radical Galvinoxyl. Finally, G. curtisii strain (GH-16-023) presented the lowest level of toxicity with a LC50 of 490.881 µg/mL against A. franciscana. These results support the potential medicinal effects of Mexican strains of G. curtisii.

An arabinose-induced enhancement of asexual reproduction and concomitant changes in metabolic state in the filamentous fungus Bipolaris maydis

l-Arabinose, a major constituent pentose of plant cell-wall polysaccharides, has been suggested to be a less preferred carbon source for fungi but to be a potential signalling molecule that can cause distinct genome-wide transcriptional changes in fungal cells. Here, we explore the possibility that this unique pentose influences the morphological characteristics of the phytopathogenic fungus Bipolaris maydis strain HITO7711. When grown on plate media under different sugar conditions, the mycelial dry weight of cultures on l-arabinose was as low as that with no sugar, suggesting that l-arabinose does not substantially contribute to vegetative growth. However, the intensity of conidiation on l-arabinose was comparable to or even higher than that on d-glucose and on d-xylose, in contrast to the poor conidiation under the no-sugar condition. To explore the physiological basis of the passive growth and active conidiation on l-arabinose, we next investigated cellular responses of the fungus to these sugar conditions. Transcriptional analysis of genes related to carbohydrate metabolism showed that l-arabinose stimulates carbohydrate utilization through the hexose monophosphate shunt (HMP shunt), a catabolic pathway parallel to glycolysis and which participates in the generation of the reducing agent NADPH (the reduced form of nicotinamide adenine dinucleotide phosphate). Then, the HMP shunt was impaired by disrupting the related gene BmZwf1, which encodes glucose-6-phosphate dehydrogenase in this fungus. The resulting mutants on l-arabinose showed remarkably decreased conidiation, but a conversely increased mycelial dry weight compared with the wild-type. Our study demonstrates that l-arabinose acts to enhance resource allocation to asexual reproduction in B. maydis HITO7711 at the cost of vegetative growth, and suggests that this is mediated by the concomitant stimulation of the HMP shunt.

The mycorrhizal community of the epiphytic orchid Thrixspermum japonicum is strongly biased toward a single Ceratobasidiaceae fungus, despite a wide range of fungal partners

PREMISE

Orchids depend primarily on mycorrhizal fungi to obtain nutrients throughout their life cycle. Epiphytic orchids account for 69% of orchid diversity. The unstable availability of water and nutrients in their arboreal habitats often results in severe water and nutrient stresses. Consequently, mycorrhizal associations may be important for the survival of epiphytic orchids, but our understanding thereof remains limited. Here, we investigated the mycorrhizal community in a single epiphytic orchid species, using more samples than in any previous study.

METHODS

We assessed the mycorrhizal communities of Thrixspermum japonicum, one of the most common epiphytic orchids in the temperate region of Japan. In total, 144 individuals were collected from 28 host tree species at 20 sites across 1300 km. The mycorrhizal fungi were identified based on nuclear ribosomal DNA internal transcribed spacer sequences and assigned operational taxonomic units (OTUs) based on 97% sequence similarity.

RESULTS

We obtained 24 OTUs; 9 belonged to the Ceratobasidiaceae and 15 to the Tulasnellaceae. These OTUs are widely distributed throughout the phylogenetic trees of the two fungal families. However, a single Ceratobasidiaceae OTU accounted for 49.7% of all fungal sequences and was predominant in samples from 15 host tree species and 12 sites.

CONCLUSIONS

Our results imply that despite having a broad range of mycorrhizal partners, T. japonicum was predominantly associated with a single fungal taxon at most of the sites among the host-tree species investigated. These findings contribute to elucidating mycorrhizal symbiosis in epiphytic habitats.

Identification of a SNP and development of a PCR-based allele-specific marker of the sporulation-deficient (sporeless) trait of the Tamogitake 108Y2D mutant using next-generation sequencing

The mass scattering of basidiospores during the cultivation of edible mushrooms causes serious problems, such as allergic reactions in workers. Sporulation-deficient (sporeless) cultivars would be very useful for preventing these issues. We aimed to identify the single-nucleotide polymorphism (SNP) that is responsible for the single dominant sporeless mutation of the Tamogitake 108Y2D mutant using next-generation sequencing (NGS) and TILLING technology and to develop an allele-specific PCR marker for sporeless breeding. By comparing the sequences of the wild-type and its mutant genomes, we identified 685 mutation loci in gene regions and pinpointed one SNP only consistent with sporeless phenotype for 105 segregants, i.e., a C to T located at position 1,950 of the exonic region of a putative fungal transcription factor that generated a stop codon. We developed an allele-specific marker based on the identified SNP, and its high practicality was validated using tests against progenies from several hybrids and wild isolates from different geographical origins. Thus, the allele-specific PCR marker developed here will be useful for marker-assisted selection in the breeding of the sporeless trait of this mushroom. Furthermore, the technical success of SNP identification and marker development based on NGS genome data can help achieve efficient mutation breeding in mushrooms.

Morphologically similar but not closely related: the long-spored species of Subulicystidium (Trechisporales, Basidiomycota)

Species boundaries and geographic distribution of corticioid fungi (resupinate Basidiomycota) are often poorly known. Our recent study on Subulicystidium showed that species diversity in this genus is at least twice as high as previously recognized. This re-estimation of the species diversity was based on a study of only a part of the genus. The present study sheds light on molecular and morphological diversity of three more species. We generated 27 ITS and 24 28S nuclear ribosomal DNA sequences from 49 specimens labelled as Subulicystidium cochleum, S. longisporum and S. perlongisporum and collected in distant geographic localities. We assessed pairwise dissimilarities and phylogenetic relationships of DNA sequences with Bayesian and maximum likelihood methods. We correlated phylogenetic information with morphological data on spores and cystidia. We found that the three species are not closely related, despite their similarity in spore shape and size. In one of the species, S. perlongisporum, we detected the presence of two sympatric lineages. These lineages are not morphologically distinct, except for a small difference in the mean length of cystidia. Our study provides a further example of transoceanic species distribution in Agaricomycetes.