Wood-inhabiting fungi are a cosmopolitan group and show a rich diversity, growing in the vegetation of boreal, temperate, subtropical, and tropical regions. Xylodon grandineus, X. punctus, and X. wenshanensis spp. nov. were found in the Yunnan–Guizhou Plateau, China, suggested here to be new fungal species in light of their morphology and phylogeny. Xylodon grandineus is characterized by a grandinioid hymenophore and ellipsoid basidiospores; X. punctus has a membranous hymenophore, a smooth hymenial surface with a speckled distribution, and absent cystidia; X. wenshanensis has a grandinioid hymenophore with a cream to slightly buff hymenial surface and cystidia of two types. Sequences of the ITS and nLSU rRNA markers of the studied samples were generated, and phylogenetic analyses were performed using the maximum likelihood, maximum parsimony, and Bayesian inference methods. After a series of phylogenetic studies, the ITS+nLSU analysis of the order Hymenochaetales indicated that, at the generic level, six genera (i.e., Fasciodontia, Hastodontia, Hyphodontia, Lyomyces, Kneiffiella, and Xylodon) should be accepted to accommodate the members of Hyphodontia sensu lato. According to a further analysis of the ITS dataset, X. grandineus was retrieved as a sister to X. nesporii; X. punctus formed a monophyletic lineage and then grouped with X. filicinus, X. hastifer, X. hyphodontinus, and X. tropicus; and X. wenshanensis was a sister to X. xinpingensis.

https://www.mdpi.com/2309-608X/8/4/405/pdf?version=1650330425

Phylogenetic and Taxonomic Analyses of Three New Wood-Inhabiting Fungi of Xylodon (Basidiomycota) in a Forest Ecological System

Pleurotus eryngii (king oyster mushroom) is a popular and economically valuable edible mushroom; however, it suffers from various bacterial diseases, including soft rot disease caused by the bacterium Erwinia beijingensis. Here, we examined bacterial infection of the mushroom through morphological and ultrastructural observations as well as transcriptome analysis. ABSTRACT Pleurotus eryngii (king oyster mushroom) is a commercially important mushroom with high nutritional and economic value. However, soft rot disease, caused by the pathogenic bacterium Erwinia beijingensis, poses a threat to its quality and production. Morphological and ultrastructural observations of P. eryngii were conducted at early, middle, and late stages of infection. At 2 days postinoculation (dpi), small yellow spots on the fruiting body were observed. The infected tissue displayed hyphal deformations and breaks at 5 dpi. At 9 dpi, damage to cell wall integrity and absence of intact cellular organelles were observed and the diseased fruiting bodies were unable to grow normally. Transcriptome analysis identified 4,296 differentially expressed genes in the fruiting body following infection. In fact, broad transcriptional reprogramming was observed in infected fruiting bodies compared to controls. The affected pathways included antioxidant systems, peroxisome biogenesis, autophagy, and oxidation-reduction. More specifically, pex genes were downregulated during infection, indicating impaired peroxisome homeostasis and redox balance. Additionally, genes encoding chitinase, β-1,3-glucanase, and proteases associated with cell wall degradation were upregulated in infected P. eryngii. This study provides insights into the responses of P. eryngii during soft rot disease and facilitates the understanding of the pathogenic process of bacteriosis in mushrooms. IMPORTANCE Pleurotus eryngii (king oyster mushroom) is a popular and economically valuable edible mushroom; however, it suffers from various bacterial diseases, including soft rot disease caused by the bacterium Erwinia beijingensis. Here, we examined bacterial infection of the mushroom through morphological and ultrastructural observations as well as transcriptome analysis. Pathogen attack damaged the cell structure of P. eryngii, including the cell wall, and also induced high levels of reactive oxygen species. These results were reflected in differential gene expression in P. eryngii as a response to the pathogenic bacteria, including genes involved in antioxidant systems, peroxisome biogenesis, autophagy, oxidation-reduction, ribosome biogenesis, and cell-wall degradation, among others. This study provides insights into the structural and molecular responses of P. eryngii during soft rot disease, improving our understanding and the potential control of the pathogenic process of bacteriosis in mushrooms.

Bacterial Infection Induces Ultrastructural and Transcriptional Changes in the King Oyster Mushroom (Pleurotus eryngii)

Fungi are widely exploited for large-scale production in the biotechnological industry to produce a diverse range of substances due to their versatility and relative ease of growing on various substrates. The occurrence of a phenomenon-the so-called fungal strain degeneration-leads to the spontaneous loss or decline of production capacity and results in an economic loss on a tremendous scale. Some of the most commonly applied genera of fungi in the biotechnical industry, such as Aspergillus, Trichoderma, and Penicillium, are threatened by this phenomenon. Although fungal degeneration has been known for almost a century, the phenomenon and its underlying mechanisms still need to be understood. The proposed mechanisms causing fungi to degenerate can be of genetic or epigenetic origin. Other factors, such as culture conditions, stress, or aging, were also reported to have an influence. This mini-review addresses the topic of fungal degeneration by describing examples of productivity losses in biotechnical processes using Aspergillus niger, Aspergillus oryzae, Trichoderma reesei, and Penicillium chrysogenum. Further, potential reasons, circumvention, and prevention methods are discussed. This is the first mini-review which provides a comprehensive overview on this phenomenon in biotechnologically used fungi, and it also includes a collection of strategies that can be useful to minimize economic losses which can arise from strain degeneration. KEY POINTS: • Spontaneous loss of productivity is evident in many fungi used in biotechnology. • The properties and mechanisms underlying this phenomenon are very versatile. • Only studying these underlying mechanisms enables the design of a tailored solution. 

/pdf/the-phenomenon-of-strain-degeneration-in-biotechnologically-224bavwg.pdf

The phenomenon of strain degeneration in biotechnologically relevant fungi

Edible fungi are not only delicious but are also rich in nutritional and medicinal value, which is highly sought after by consumers. As the edible fungi industry continues to rapidly advance worldwide, particularly in China, the cultivation of superior and innovative edible fungi strains has become increasingly pivotal. Nevertheless, conventional breeding techniques for edible fungi can be arduous and time-consuming. CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/CRISPR-associated nuclease 9) is a powerful tool for molecular breeding due to its ability to mediate high-efficiency and high-precision genome modification, which has been successfully applied to many kinds of edible fungi. In this review, we briefly summarized the working mechanism of the CRISPR/Cas9 system and highlighted the application progress of CRISPR/Cas9-mediated genome-editing technology in edible fungi, including Agaricus bisporus, Ganoderma lucidum, Flammulina filiformis, Ustilago maydis, Pleurotus eryngii, Pleurotus ostreatus, Coprinopsis cinerea, Schizophyllum commune, Cordyceps militaris, and Shiraia bambusicola. Additionally, we discussed the limitations and challenges encountered using CRISPR/Cas9 technology in edible fungi and provided potential solutions. Finally, the applications of CRISPR/Cas9 system for molecular breeding of edible fungi in the future are explored.

/pdf/application-progress-of-crispr-cas9-genome-editing-1jomjyc5.pdf

Application progress of CRISPR/Cas9 genome-editing technology in edible fungi

Strain degeneration has been defined as a decrease or loss in the yield of important commercial traits resulting from subsequent culture, which ultimately leads to Reactive Oxygen Species (ROS) production. Pleurotus ostreatus is a lignin-producing nematophagous edible mushroom. Mycelia for mushroom production are usually maintained in subsequent culture in solid media and frequently show symptoms of strain degeneration. The dikaryotic strain P. ostreatus (DkN001) has been used in our lab as a model organism for different purposes. Hence, different tools have been developed to uncover genetic and molecular aspects of this fungus. In this work, strain degeneration was studied in a full-sib monokaryotic progeny of the DkN001 strain with fast (F) and slow (S) growth rates by using different experimental approaches (light microscopy, malondialdehyde levels, whole-genome transcriptome analysis, and chitosan effect on monokaryotic mycelia). The results obtained showed that: (i) strain degeneration in P. ostreatus is linked to oxidative stress, (ii) the oxidative stress response in monokaryons is genotype dependent, (iii) stress and detoxifying genes are highly expressed in S monokaryons with symptoms of strain degeneration, (iv) chitosan addition to F and S monokaryons uncovered the constitutive expression of both oxidative stress and cellular detoxifying genes in S monokaryon strains which suggest their adaptation to oxidative stress, and (v) the overexpression of the cell wall genes, Uap1 and Cda1, in S monokaryons with strain degeneration phenotype indicates cell wall reshaping and the activation of High Osmolarity Glycerol (HOG) and Cell Wall Integrity (CWI) pathways. These results could constitute a hallmark for mushroom producers to distinguish strain degeneration in commercial mushrooms.

Strain Degeneration in Pleurotus ostreatus: A Genotype Dependent Oxidative Stress Process Which Triggers Oxidative Stress, Cellular Detoxifying and Cell Wall Reshaping Genes.

María Ibañez-Vea

Papers

Strain Degeneration in Pleurotus ostreatus: A Genotype Dependent Oxidative Stress Process Which Triggers Oxidative Stress, Cellular Detoxifying and Cell Wall Reshaping Genes.