Five new epiphytic species of Vishniacozyma (Bulleribasidiaceae, Tremellales) from China

The genus Vishniacozyma, globally distributed, encompasses numerous epiphytic and endophytic species. In this study, five new species are proposed to accommodate eleven yeast strains isolated from leaves of different plants: V.diospyri sp. nov. (holotype CICC 33574T), V.guiyangensis sp. nov. (holotype CICC 33569T), V.pingtangensis sp. nov. (holotype CICC 33596T), V.eriobotryae sp. nov. (holotype GDMCC 2.312T), and V.tianchiensis sp. nov. (holotype CICC 33617T) using phenotypic and phylogenetic characters. Phylogenetic analysis was based on the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit (LSU) rRNA gene. Illustrations and descriptions of these five taxa are provided, along with comparative analyses with closely related species within the genus. This research highlights the considerable diversity of Vishniacozyma species in China and contributes valuable data for future investigations in fungal systematics and evolution.

Vishniacozyma siamensis sp. nov., a new anamorphic tremellomycetous yeast species isolated from a mangrove forest in Thailand

Six strains (DMKU-SG26, DMKU-SG42, DMKU-SYM22, DMKU-RG41, DMKU-RX317 and DMKU-RGM25) representing a novel basidiomycetous yeast species were isolated from leaf surfaces of mangrove plants collected in Thailand. Pairwise sequence analysis indicated that the six strains either had identical nucleotide substitution in the D1/D2 domains of the large subunit (LSU) rRNA gene sequences or differed by one to three nucleotide(s). They also had identical or differed by one to five nucleotide substitution(s) in the internal transcribed spacer (ITS) regions. blastn searches of the GenBank database revealed that the six strains were closely related to the holotype of type strains of Vishniacozyma peneaus, V. terrae, V. phoenicis, V. taiwanica and V. europaea, but with 6-15 (1.14-2.48%) and 16-26 (5.4-8.8%) nucleotide substitutions in the D1/D2 domains of the LSU rRNA gene and the ITS regions, respectively. Phylogenetic analysis based on the concatenated sequences of the ITS regions and D1/D2 domains of the LSU rRNA gene showed that these strains are placed in the Vishniacozyma clade but were at a distinctly different position from the other recognized species of the genus. Based on the phylogenetic analysis and phenotypic characteristics, these six strains are a novel species of the genus Vishniacozyma, for which the name Vishniacozyma siamensis sp. nov. is proposed to accommodate them. The holotype is TBRC 18499T and the ex-type culture is PYCC 10042 (=DMKU-SG26). The MycoBank number of the novel species is MB 855838.

Peltigera lichens as sources of uncharacterized cultured basidiomycete yeasts

Lichens represent one of the most successful examples of symbiosis. They are constituted by the association between a dominant fungus (i.e., the mycobiont), one or more photosynthetic partners (algae or cyanobacteria), and harbor an array of associated microorganisms, including bacteria and fungi. The associated fungal communities in lichens, known as the "lichen mycobiome", are composed of both ascomycetes and basidiomycetes, including filamentous and yeast taxa. Recently, basidiomycete yeasts have received considerable attention as a much-overlooked source of diversity within the lichen mycobiome, with hypothesized roles in lichen symbiosis. This study surveyed the diversity of cultivable basidiomycete yeasts associated with Peltigera lichens across southern Chile. A phylogenetic study based on sequences of 179 yeast isolates allowed the identification of 29 taxa from 13 genera in the classes Agaricostilbomycetes, Cystobasidiomycetes, Microbotryomycetes, and Tremellomycetes, with the latter being the most represented. This research revealed several yeast species, including members of the genera Boekhoutia and Goffeauzyma, in lichens for the first time, thereby expanding our understanding of lichen-associated fungal diversity. In addition, four new cultivable species isolated from Peltigera are formally described. These are Boekhoutia peltigerae sp. nov., Cystobasidium chilense sp. nov., Genolevuria patagonica sp. nov. and Pseudotremella navarinensis sp. nov. These results highlight the role of lichens as reservoirs of uncharacterized basidiomycete yeasts.

Vishniacozyma pseudocarnescens sp. nov., a new anamorphic tremellomycetous yeast species

Three strains belonging to the basidiomycetous yeast genus Vishniacozyma were isolated from marine water samples collected from intertidal zones in Liaoning province, northeast China. Phylogenetic analyses based on the sequences of the small subunit (SSU) ribosomal DNA (rDNA), the D1/D2 domain of the large subunit (LSU) ribosomal DNA (rDNA), the internal transcribed spacer region (ITS), the two subunits of DNA polymerase II (RPB1 and RPB2), the translation elongation factor 1-α (TEF1), and the mitochondrial gene cytochrome b (CYTB) showed that these strains together with 20 strains from various geographic and ecological origins from other regions of the world represent a novel species in the genus Vishniacozyma. We propose the name Vishniacozyma pseudocarnescens sp. nov. (holotype CGMCC 2.6457) for the new species, which differs phenotypically from its close relatives V. carnescens, V. tephrensis, and V. victoriae by its ability to grow at 30 °C and on 50 % (w/v) glucose-yeast extract agar.

The first two mitochondrial genomes from Apiotrichum reveal mitochondrial evolution and different taxonomic assignment of Trichosporonales

Apiotrichum is a diverse anamorphic basidiomycetous yeast genus, and its mitogenome characterization has not been revealed. In this study, we assembled two Apiotrichum mitogenomes and compared them with mitogenomes from Agaricomycotina, Pucciniomycotina and Ustilaginomycotina. The mitogenomes of Apiotrichum gracile and A. gamsii comprised circular DNA molecules, with sizes of 34,648 bp and 38,096 bp, respectively. Intronic regions were found contributed the most to the size expansion of A. gamsii mitogenome. Comparative mitogenomic analysis revealed that 6.85-38.89% of nucleotides varied between tRNAs shared by the two Apiotrichum mitogenomes. The GC content of all core PCGs in A. gamsii was lower than that of A. gracile, with an average low value of 4.97%. The rps3 gene differentiated the most among Agaricomycotina, Pucciniomycotina and Ustilaginomycotina species, while nad4L gene was the most conserved in evolution. The Ka/Ks values for cob and rps3 genes were > 1, indicating the two genes may be subjected to positive selection in Agaricomycotina, Pucciniomycotina and Ustilaginomycotina. Frequent intron loss/gain events and potential intron transfer events have been detected in evolution of Agaricomycotina, Pucciniomycotina and Ustilaginomycotina. We further detected large-scale gene rearrangements between the 19 mitogenomes from Agaricomycotina, Pucciniomycotina and Ustilaginomycotina, and fifteen of the 17 mitochondrial genes shared by Apiotrichum varied in gene arrangements. Phylogenetic analyses based on maximum likelihood and Bayesian inference methods using a combined mitochondrial gene dataset revealed different taxonomic assignment of two Apiotrichum species, wherein A. gamsii had a more closely relationship with Trichosporon asahii. This study served as the first report on mitogenomes from the genus Apiotrichum, which promotes the understanding of evolution, genomics, and phylogeny of Apiotrichum.

First two mitochondrial genomes for the order Filobasidiales reveal novel gene rearrangements and intron dynamics of Tremellomycetes

In the present study, two mitogenomes from the Filobasidium genus were assembled and compared with other Tremellomycetes mitogenomes. The mitogenomes of F. wieringae and F. globisporum both comprised circular DNA molecules, with sizes of 27,861 bp and 71,783 bp, respectively. Comparative mitogenomic analysis revealed that the genetic contents, tRNAs, and codon usages of the two Filobasidium species differed greatly. The sizes of the two Filobasidium mitogenomes varied greatly with the introns being the main factor contributing to mitogenome expansion in F. globisporum. Positive selection was observed in several protein-coding genes (PCGs) in the Agaricomycotina, Pucciniomycotina, and Ustilaginomycotina species, including cob, cox2, nad2, and rps3 genes. Frequent intron loss/gain events were detected to have occurred during the evolution of the Tremellomycetes mitogenomes, and the mitogenomes of 17 species from Agaricomycotina, Pucciniomycotina, and Ustilaginomycotina have undergone large-scale gene rearrangements. Phylogenetic analyses based on Bayesian inference and the maximum likelihood methods using a combined mitochondrial gene set generated identical and well-supported phylogenetic trees, wherein Filobasidium species had close relationships with Trichosporonales species. This study, which is the first report on mitogenomes from the order Filobasidiales, provides a basis for understanding the genomics, evolution, and taxonomy of this important fungal group.

Non-target impacts of fungicide disturbance on phyllosphere yeasts in conventional and no-till management

Fungicides reduce fungal pathogen populations and are essential to food security. Understanding the impacts of fungicides on crop microbiomes is vital to minimizing unintended consequences while maintaining their use for plant protection. However, fungicide disturbance of plant microbiomes has received limited attention, and has not been examined in different agricultural management systems. We used amplicon sequencing of fungi and prokaryotes in maize and soybean microbiomes before and after foliar fungicide application in leaves and roots from plots under long-term no-till and conventional tillage management. We examined fungicide disturbance and resilience, which revealed consistent non-target effects and greater resiliency under no-till management. Fungicides lowered pathogen abundance in maize and soybean and decreased the abundance of Tremellomycetes yeasts, especially Bulleribasidiaceae, including core microbiome members. Fungicide application reduced network complexity in the soybean phyllosphere, which revealed altered co-occurrence patterns between yeast species of Bulleribasidiaceae, and Sphingomonas and Hymenobacter in fungicide treated plots. Results indicate that foliar fungicides lower pathogen and non-target fungal abundance and may impact prokaryotes indirectly. Treatment effects were confined to the phyllosphere and did not impact belowground microbial communities. Overall, these results demonstrate the resilience of no-till management to fungicide disturbance, a potential novel ecosystem service provided by no-till agriculture.

Tremellomycetes Yeasts in Kernel Ecological Niche: Early Indicators of Enhanced Competitiveness of Endophytic and Mycoparasitic Symbionts against Wheat Pathobiota

Tremellomycetes rDNA sequences previously detected in wheat kernels by MiSeq were not reliably assigned to a genus or clade. From comparisons of ribosomal internal transcribed spacer region (ITS) and subsequent phylogenetic analyses, the following three basidiomycetous yeasts were resolved and identified: Vishniacozymavictoriae, V. tephrensis, and an undescribed Vishniacozyma rDNA variant. The Vishniacozyma variant’s clade is evolutionarily close to, but phylogenetically distinct from, the V. carnescens clade. These three yeasts were discovered in wheat kernel samples from the Canadian prairies. Variations in relative Vishniacozyma species abundances coincided with altered wheat kernel weight, as well as host resistance to chemibiotrophic Tilletia (Common bunt—CB) and necrotrophic Fusarium (Fusarium head blight—FHB) pathogens. Wheat kernel weight was influenced by the coexistence of Vishniacozyma with endophytic plant growth-promoting and mycoparasitic biocontrol fungi that were acquired by plants. Kernels were coated with beneficial Penicillium endophyte and Sphaerodes mycoparasite, each of which had different influences on the wild yeast population. Its integral role in the kernel microbiome renders Vishniacozyma a measurable indicator of the microbiome–plant interaction. The ability of NGS technology to detect specific endophytic DNA variants and early changes in dynamics among symbionts within the kernel ecological niche enables the prediction of crop disease emergence, suggesting that advanced microbiological testing may be a potentially useful tool for both phytoprotection and more efficient wheat breeding programs.

Vishniacozyma changhuana sp. nov., and Vishniacozyma taiwanica sp. nov., two novel yeast species isolated from mangrove forests in Taiwan

Mangroves grow in the intertidal zone, which alternates between fresh water and sea water, with abundant bioresources. In mangrove habitats, yeasts play an important role in the decomposition of organic matter, and such nutrient cycling has high ecological importance. During a study of the diversity of yeast from Taiwan mangroves, seven strains of basidiomycetous yeasts were isolated and these yeasts represent two novel yeast species belonging to the genus Vishniacozyma. According to the sequences of the D1/D2 domain of large subunit (LSU) rRNA and the internal transcribed spacer (ITS) region, these seven strains could be clearly classified into two groups representing two individual, distinct species. Strains HM5L06, HM6L07, HM11L11 and BJ3S01, differed from their closest relative species Vishniacozyma phoenicis by 4-5 nt substitutions (no gaps) in the sequences of the D1/D2 domain of LSU rRNA and by 23 nt substitutions (10 gaps) in the ITS region. Strains HM6L11, HM7L02 and HM8L19, differed from their closest relative species Vishniacozyma penaeus by 7 nt substitutions (one gap) in the sequences of the D1/D2 domain of LSU rRNA and by 27 nt substitutions (12 gaps) in the ITS region. The scientific names of Vishniacozyma taiwanica sp. nov. and Vishniacozyma changhuana sp. nov. are proposed for these strains. The holotypes are Vishniacozyma taiwanica BCRC 23477^T (ex-type HM5L06=CBS 16558; MycoBank number MB837428) and Vishniacozyma changhuana BCRC 23478^T (ex-type HM6L11=CBS 16556; MycoBank number MB837429).

Species Identification in Plant-Associated Prokaryotes and Fungi Using DNA

Species names are fundamental to managing biological information. The surge of interest in microbial diversity has resulted in an increase in the number of microbes that need to be identified and assigned a species name. This article provides an introduction to the principles of DNA-based identification of Archaea and Bacteria traditionally known as prokaryotes, and Fungi, the Oomycetes and other protists, collectively referred to as fungi. The prokaryotes and fungi are the most commonly studied microbes from plants, and we introduce the most relevant concepts of prokaryote and fungal taxonomy and nomenclature. We first explain how prokaryote and fungal species are defined, delimited, and named, and then summarize the criteria and methods used to identify prokaryote and fungal organisms to species.

Heterocephalacria sinensis sp. nov., Phaeotremella lacus sp. nov. and Solicoccozyma aquatica sp. nov., three novel basidiomycetous yeast species isolated from crater lakes

The Arxan-Chaihe volcanic field of the Da Hinggan mountains in north-East PR China hosts various typical crater lakes. In this study we performed a yeast diversity survey using water sampled from five crater lakes and a total of 122 yeast strains belonging to 33 species of 25 genera were isolated. Three strains, TFL1-L, TFL2B and ATC4C, were identified as three novel species belonging to the Tremellomycetes based on a multiple gene phylogeny and on the comparison of physiological data. A phylogenetic study employing the sequences of seven genes indicated that the new species were more related to three separated phylogenetic lineages of the Tremellomycetes and their closest relatives were Heterocephalacria arrabidensis, Phaeotremella skinneri and Solicoccozyma keelungensis. The divergence values of the D1/D2 domain of LSU sequences of strains TFL1-L, TFL2B and ATC4C from H. arrabidensis CBS 8678^T, P. skinneri CBS 5029^T and S. keelungensisSN-82^T were 4.8，3.4，2.1 %， respectively. The divergence values of the sequences of ITS regions between strains TFL1-L, TFL2B and ATC4C and their close relatives (H. arrabidensis, P. skinneri and S. keelungensis) were 16.1, 5.9 and 8.1  %, respectively. Moreover, the three strains differed from their phylogenetic neighbours by the ability to grow on distinct carbon and nitrogen sources. On the basis of these findings, it is suggested that these strains represent three novel species for which the names Heterocephalacria sinensis sp. nov. (holotype CGMCC 2.5595), Phaeotremella lacus sp. nov. (holotype CGMCC 2.5580) and Solicoccozyma aquatica sp. nov. (holotype CGMCC 2.5574) are proposed.