Molecular systematics and taxonomic overview of the bird's nest fungi (Nidulariaceae)

Ex Situ Conservation, DNA Barcoding and Enzymatic Potential Evaluation of Macrofungi (Basidiomycota, Ascomycota) from Vietnam

The diversity and resource potential of macroscopic fungi in tropical regions remain understudied. Vietnam, being in a biodiversity hotspot, has a large number of new fungal species that are of interest for biotechnology and medicine. The presence of a large number of protected areas in Vietnam creates favorable opportunities for the study and ex situ conservation of tropical biodiversity. From 2012 to 2023, 785 strains of macrofungi from National Parks of Vietnam were preserved in the LE-BIN collection, 327 of which were barcoded with the sequences deposited in the NCBI GenBank. A taxonomic analysis demonstrated that many of the preserved isolates are potentially new or poorly studied species, representing a useful resource for taxonomical studies and a search for new medicinal mushrooms. More than 180 strains were studied for the first time for growth rate and enzymatic activities. Of these, 53 strains showed high growth rate, 43-high cellulolytic activity, 73-high oxidative enzymes activity, and 27 showed high proteolytic activity, making them promising candidates for biotechnological and medical applications and opening new opportunities for sustainable biomass management, discovery of new enzymes and bioactive substances, development of new drugs and efficient plant waste treatment technologies. The results confirm the importance of the ex situ conservation of fungal diversity in tropical regions as a valuable source for scientific and commercial applications and suggest certain new active strains for biotechnological study.

Saprotrophic Wood Decay Ability and Plant Cell Wall Degrading Enzyme System of the White Rot Fungus Crucibulum laeve: Secretome, Metabolome and Genome Investigations

The basidiomycete Crucibulum laeve strain LE-BIN1700 (Agaricales, Nidulariaceae) is able to grow on agar media supplemented with individual components of lignocellulose such as lignin, cellulose, xylan, xyloglucan, arabinoxylan, starch and pectin, and also to effectively destroy and digest birch, alder and pine sawdust. C. laeve produces a unique repertoire of proteins for the saccharification of the plant biomass, including predominantly oxidative enzymes such as laccases (family AA1_1 CAZymes), GMC oxidoreductases (family AA3_2 CAZymes), FAD-oligosaccharide oxidase (family AA7 CAZymes) and lytic polysaccharide monooxygenases (family LPMO X325), as well as accompanying acetyl esterases and loosenine-like expansins. Metabolomic analysis revealed that, specifically, monosaccharides and carboxylic acids were the key low molecular metabolites in the C. laeve culture liquids in the experimental conditions. The proportion of monosaccharides and polyols in the total pool of identified compounds increased on the sawdust-containing media. Multiple copies of the family AA1_1, AA3_2, AA7 and LPMOs CAZyme genes, as well as eight genes encoding proteins of the YvrE superfamily (COG3386), which includes sugar lactone lactonases, were predicted in the C. laeve genome. According to metabolic pathway analysis, the litter saprotroph C. laeve can catabolize D-gluconic and D-galacturonic acids, and possibly other aldonic acids, which seems to confer certain ecological advantages.

Enhanced salt tolerance in Glycyrrhiza uralensis Fisch. via Bacillus subtilis inoculation alters microbial community

The widespread prevalence of saline environments poses a significant global environmental challenge. Salt stress, induced by saline soils, disrupts soil microecology and affects the plant-microbe-soil cycling process. Utilizing microbial fungicides stands as a primary strategy to mitigate salt stress-induced damage to plants and soils. This study investigated the influence of Bacillus subtilis (Bs) inoculation on the microbial community, assembly processes, and functional changes in bacteria and fungi in Glycyrrhiza uralensis Fisch. (licorice) seedlings under varying salt stress levels, primarily employing microbiomics techniques. Soil enzyme activities displayed a declining trend with increasing salt stress, which was mitigated by Bs inoculation. Microbiome analysis revealed a significant increase in bacterial and fungal operational taxonomic units, particularly in Ascomycetes and Nitrogen-fixing Bacteria, thereby enhancing soil denitrification. The abundance of Proteobacteria, Actinobacteriota, Bacteroidota, and Firmicutes in bacteria, as well as Ascomycota in fungi, increased with higher salt stress levels, a process facilitated by Bs inoculation. However, functional predictions indicated a reduction in the relative abundance of Dung Saprotrophs with Bs inoculation. Salt stress disrupted soil assembly processes, showcasing a continuous decline in diffusion limitation with increased salt concentration, where Bs inoculation reached a peak under moderate stress. In summary, this research elucidates the communication mechanism of Bs in enhancing salt tolerance in licorice from a microbiome perspective, contributing to a comprehensive understanding of abiotic and biotic factors.IMPORTANCELicorice is a herb that grows in deserts or saline soils. Enhancing the salt tolerance of licorice is necessary to maintain the quality of cultivated licorice and to ensure the supply of medicinal herbs. In the past, we have demonstrated the effectiveness of inoculation with Bacillus subtilis (Bs) to enhance the salt tolerance of licorice and revealed the key metabolic pathways for the development of salt tolerance through multi-omics. In this study, we used the microbiomics approach to reveal the plant-microbe-soil interactions at the level of inoculation of Bs affecting the dynamics of soil microbial communities from bacterial and fungal perspectives, thus bridging the interactions between biotic and abiotic factors.

Complete mitochondrial genome of the bird's nest fungus Nidula shingbaensis (Nidulariaceae, Agaricales)

Bird's nest fungi involve six different genera, but only one of these genera (i.e. Cyathus) have available mitochondrial genomes (mitogenomes) to date. In this study, we report the first mitogenome in the genus Nidula with Nidula shingbaensis K. Das & R.L. Zhao 2013 as a representative. The mitogenome is a circular molecule of 65,793 bp with a GC content of 26.2%. There are a total of 43 genes, including 14 typical protein-coding genes, 26 tRNA genes, two rRNA genes, and one free-standing intergenic open reading frame (ORF). Three introns (two in cox1 and one in cob) are present in the mitogenome, with each containing an ORF encoding for a LAGLIDADG endonuclease. Phylogenetic analysis based on mitochondrial amino acid sequences confirms the phylogenetic placement of N. shingbaensis in Nidulariaceae in Agaricales. This study serves as a springboard for future investigation on fungal evolution in Nidulariaceae.

Genome-wide characterization and metabolite profiling of Cyathus olla: insights into the biosynthesis of medicinal compounds

Cyathus olla, belonging to the genus Cyathus within the order Agaricales, is renowned for its bird's nest-like fruiting bodies and has been utilized in folk medicine. However, its genome remains poorly understood. To investigate genomic diversity within the genus Cyathus and elucidate biosynthetic pathways for medicinal compounds, we generated a high-quality genome assembly of C. olla with fourteen chromosomes. The comparative genome analysis revealed variations in both genomes and specific functional genes within the genus Cyathus. Phylogenomic and gene family variation analyses provided insights into evolutionary divergence, as well as genome expansion and contraction in individual Cyathus species and 36 typical Basidiomycota. Furthermore, analysis of LTR-RT and Ka/Ks revealed apparent whole-genome duplication (WGD) events its genome. Through genome mining and metabolite profiling, we identified the biosynthetic gene cluster (BGC) for cyathane diterpenes from C. olla. Furthermore, we predicted 32 BGCs, containing 41 core genes, involved in other bioactive metabolites. These findings represent a valuable genomic resource that will enhance our understanding of Cyathus species genetic diversity. The genome analysis of C. olla provides insights into the biosynthesis of medicinal compounds and establishes a fundamental basis for future investigations into the genetic basis of chemodiversity in this significant medicinal fungus.

On the origin of bird's nest fungi: Phylogenomic analyses of fungi in the Nidulariaceae (Agaricales, Basidiomycota)

Nidulariaceae, also known as bird's nest fungi, is an understudied group of mushroom-forming fungi. The common name is derived from their nest-like morphology. Bird's nest fungi are ubiquitous wood decomposers or saprobes on dung. Recent studies showed that species in the Nidulariaceae form a monophyletic group with five sub-clades. However, phylogenetic relationships among genera and placement of Nidulariaceae are still unclear. We present phylogenomic analyses of bird's nest fungi and related Agaricales fungi to gain insight into the evolution of Nidulariaceae. A species tree with 17 newly generated genomes of bird's nest fungi and representatives from all major clades of Agaricales was constructed using 1044 single-copy genes to explore the intergeneric relationships and pinpoint the placement of Nidulariaceae within Agaricales. We corroborated the hypothesis that bird's nest fungi are sister to Squamanitaceae, which includes mushroom-shaped fungi with a stipe and pileus that are saprobes and mycoparasites. Lastly, stochastic character mapping of discrete traits on phylogenies (SIMMAP) suggests that the ancestor of bird's nest fungi likely possessed an evanescent, globose peridium without strings attaching to the spore packets (funiculi). This analysis suggests that the funiculus was gained twice and that the persistent, cupulate peridium form was gained at least four times and lost once. However, alternative coding schemes and datasets with a wider array of Agaricales produced conflicting results during ancestral state reconstruction, indicating that there is some uncertainty in the number of peridium transitions and that taxon sampling may significantly alter ancestral state reconstructions. Overall, our results suggest that several key morphological characters of Nidulariaceae have been subject to homoplasy.

The First Five Mitochondrial Genomes for the Family Nidulariaceae Reveal Novel Gene Rearrangements, Intron Dynamics, and Phylogeny of Agaricales

The family Nidulariaceae, consisting of five genera including Cyathus, is a unique group of mushrooms commonly referred to as bird's nest fungi due to their striking resemblance to bird's nests. These mushrooms are considered medicinal mushrooms in Chinese medicine and have received attention in recent years for their anti-neurodegenerative properties. However, despite the interest in these mushrooms, very little is known about their mitochondrial genomes (mitogenomes). This study is the first comprehensive investigation of the mitogenomes of five Nidulariaceae species with circular genome structures ranging in size from 114,236 bp to 129,263 bp. Comparative analyses based on gene content, gene length, tRNA, and codon usage indicate convergence within the family Nidulariaceae and heterogeneity within the order Agaricales. Phylogenetic analysis based on a combined mitochondrial conserved protein dataset provides a well-supported phylogenetic tree for the Basidiomycetes, which clearly demonstrates the evolutionary relationships between Nidulariaceae and other members of Agaricales. Furthermore, phylogenetic inferences based on four different gene sets reveal the stability and proximity of evolutionary relationships within Agaricales. These results reveal the uniqueness of the family Nidulariaceae and its similarity to other members of Agaricales; provide valuable insights into the origin, evolution, and genetics of Nidulariaceae species; and enrich the fungal mitogenome resource. This study will help to expand the knowledge and understanding of the mitogenomes in mushrooms.

Rearranging the Bird's Nest Fungi: molecular review of internal clades in Cyathus (Nidulariaceae, Basidiomycota)

The genus Cyathus was established in 1768, but more in-depth taxonomic studies with the group only occurred after 1844. In the following years, changes in the infrageneric classification of Cyathus were proposed based mainly on morphology. With advances in phylogenetic studies, the morphological classifications were tested and a new subdivision into three groups was proposed in 2007. Based on the last two classifications, this work aims to expand and understand the internal phylogenetic relationships among the fungi of the genus Cyathus and examine how these relationships are reflected in the taxonomic classification, through molecular analyses covering most of the species in the group, based on materials obtained from type specimens deposited in major fungal collections worldwide, besides expanding sampling with tropical species. Molecular analyses followed the protocols available in the literature, including the design of specific primers for Cyathus. In the phylogenetic analysis, using Maximum Parsimony and Bayesian methods, sequences of ITS and LSU regions from 41 samples of 39 species of Cyathus, 26 were placed with some nomenclatural types. The monophyly of Cyathus was confirmed with maximum support in both tests, and the infrageneric groups of the most recent classification were unchanged, but the clade striatum showed segregation into four groups and three subgroups. The phylogenetic organization is supported morphological characters, and diagnoses are presented for each group, as well as a dichotomous key for the infrageneric separation.

Antimicrobial and Cytotoxic Cyathane-Xylosides from Cultures of the Basidiomycete Dentipellis fragilis

In our continued search for biologically active metabolites from cultures of rare Basidiomycota species, we found eight previously undescribed cyathane-xylosides from submerged cultures of Dentipellis fragilis, which were named dentifragilins A–H. In addition, the known cyathane derivatives striatal D and laxitextine A were isolated. All compounds were characterized by high-resolution electrospray ionization mass spectrometry (HR-ESIMS) as well as by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Several of the compounds exhibited significant activities in standardized cell-based assays for the determination of antimicrobial and cytotoxic effects. The discovery of cyathanes in the genus Dentipellis has chemotaxonomic implications, as this class of diterpenoids has already been shown to be characteristic for mycelial cultures of the related genera Hericium and Laxitextum, which are classified as Dentipellis in the family Hericiaceae.