Xylariales

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Xylariales
Xylaria hypoxylon.jpg
Xylaria hypoxylon
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Sordariomycetes
Subclass: Xylariomycetidae
Order: Xylariales
Nannf. (1932)
Families

See text

The Xylariales are an order of fungi within the class Sordariomycetes (also known as Pyrenomycetes), subdivision Pezizomycotina, division Ascomycota. It was the original order of the subclass Xylariomycetidae. Xylariales was circumscribed in 1932 by Swedish mycologist John Axel Nannfeldt, [1] and Xylariomycetidae by Ove Erik Eriksson and Katarina Winka in 1997.

Contents

Taxonomy

Early classifications of the Xylariales varied considerably, with taxonomists recognising anywhere from three to eleven families within the order. A milestone in understanding the order's composition came from Smith, Liew, and Hyde's 2003 molecular phylogenetics study, which established the Xylariales as a monophyletic group containing seven families: Amphisphaeriaceae, Apiosporaceae, Clypeosphaeriaceae, Diatrypaceae, Graphostromataceae, Hyponectriaceae, and Xylariaceae. [2]

During this period, fungi in the order were characterised by several common morphological features. They typically possessed well-developed stromata (compact fungal tissues) and perithecial ascomata (flask-shaped fruiting bodies) with thick walls. Their asci, which contained eight spores, featured a distinctive apical structure that stained blue in iodine (a J+ reaction), and their paraphyses (specialised sterile filaments) were free at the tips and originated from the hymenium. The ascospores were often pigmented, with germ pores or slits, and sometimes had transverse divisions or a jelly-like coating. Their asexual forms (anamorphs) were mainly hyphomycetous, producing spores through a simple, budding process called holoblastic conidiation. [2]

Historical taxonomic debates centred around several key issues. The Myelospermataceae, which was tentatively included by some authors in the early 2000s, lacked sufficient molecular evidence for definitive placement. Earlier proposals to elevate certain groups to ordinal status (such as Amphisphaeriales and Diatrypales) were rejected based on molecular evidence. The Apiosporaceae's inclusion, formally proposed in 1998, represented one of the newer additions to the order at the time. [2]

The early molecular studies of the 2000s, while groundbreaking in establishing the monophyly of the order, also revealed limitations in using ribosomal DNA sequences for resolving family-level relationships within the Xylariales. This suggested either a relatively recent evolution of the group or slower evolutionary rates compared to other fungal orders. The relatively low genetic variation observed in commonly used molecular markers presented challenges for understanding the precise relationships between families, leaving many questions about internal phylogenetic structure unresolved. [2] More recent molecular studies have revised and enhanced the understanding of relationships within the order, such as the 2018 study that revised the families Graphostromataceae, Hypoxylaceae, Lopadostomataceae and Xylariaceae. [3] DNA analysis in 2018 confirmed the placement of the order and subclass, as sister to the order Amphisphaeriales in the subclass Xylariomycetidae. [4] [5]

The Xylariales represents a morphologically diverse group of fungi characterised by their complex stromatic structures and ecological roles as endophytes, pathogens, or saprobes. Molecular phylogenetic analyses suggest that Xylariales diverged from the related order Amphisphaeriales approximately 154 million years ago (MYA), during the Jurassic period, with the crown group of Xylariales estimated to have appeared around 147 MYA. This evolutionary timeline aligns with important diversification events, including the development of novel stromatic forms and pigmentation in ascospores, traits that distinguish many Xylariales species. [6]

Ancestral state reconstruction studies indicate that early members of Xylariales likely had inconspicuous, immersed ascomata with hyaline, septate ascospores lacking germ slits. Over time, these ancestral traits evolved into the more conspicuous and diverse stromatic structures observed in extant species, reflecting adaptations to varied ecological niches. Today, Xylariales is a highly polyphyletic group, encompassing families with considerable morphological and ecological diversity. Ongoing phylogenetic research continues to refine the taxonomy of the order, revealing previously unrecognised lineages and resolving uncertainties about its classification​. [6]

Genomics and mating systems

Genomic analyses of fungi in Xylariales have revealed an atypical organisation of mating type genes, diverging significantly from other members of the Pezizomycotina. Surveys of genomes from multiple Xylariales species, including economically important genera such as Xylaria and Daldinia , failed to identify canonical mating-type genes MAT1-1-1 and MAT1-1-2. While homologs of MAT1-2-1 and MAT1-1-3 genes were detected, these appear to be highly divergent, with some performing functions unrelated to mating. This suggests that mating and sexual development in Xylariales are controlled by mechanisms distinct from those observed in related fungal groups. The absence of significant divergence of traditional mating-type regions indicates potential evolutionary adaptations within Xylariales. It is hypothesised that these fungi might employ unisexual reproduction or alternative regulatory pathways for sexual development. [7]

Secondary metabolism

Xylaria cubensis Xylaria cubensis 741834.jpg
Xylaria cubensis

Fungi in the order Xylariales, particularly within the families Xylariaceae and Hypoxylaceae, are prolific producers of secondary metabolites, many of which exhibit bioactive properties. These compounds, often isolated from stromata and mycelial cultures, include unique carbon skeletons that have potential applications in pharmaceuticals, agrochemicals, and biological control. For example, the endophytic Xylariales have shown strong antagonistic effects against plant pathogens, making them candidates for developing environmentally friendly pest control solutions. Advances in genome sequencing have facilitated the identification of biosynthetic gene clusters, revealing insights into the molecular basis of these metabolites and opening new possibilities for synthetic biology applications​. [8]

Secondary metabolites produced by Xylariales encompass a broad spectrum of chemical classes, including terpenoids, polyketides, and nonribosomal peptides. Noteworthy discoveries include cytochalasans, which exhibit antifungal, cytotoxic, and phytotoxic properties. Some species, such as Xylaria cubensis , produce compounds with potent herbicidal activities, while others, like Hypoxylon fragiforme , generate cytochalasans that disrupt the cytoskeleton of eukaryotic cells in a reversible or irreversible manner depending on the compound. [8]

The study of secondary metabolism in Xylariales has also contributed to advances in fungal taxonomy. For example, the production of specific metabolites, combined with molecular phylogenetic techniques, has clarified the evolutionary relationships within this group. These efforts have led to the reclassification of genera and the identification of new species. This integrated approach, which combines chemical, genetic, and ecological data, continues to expand the understanding of the functional biodiversity of Xylariales and their role in natural ecosystems. [8]

Families

The collaborative fungal classification compilation The 2024 Outline of Fungi and fungus-like taxa include 22 families and 164 genera in the Xylariales. [9]

Genera of uncertain placement

There are many genera in the Xylariales that are of uncertain familial placement (incertae sedis). [9]

Related Research Articles

<span class="mw-page-title-main">Hypocreales</span> Order of fungi

The Hypocreales are an order of fungi within the class Sordariomycetes. In 2008, it was estimated that it contained some 237 genera, and 2647 species in seven families. Since then, a considerable number of further taxa have been identified, including an additional family, the Stachybotryaceae. Wijayawardene et al. in 2020 added more families and genera to the order. According to the Catalog of Life, As of April 2021 the Hypocreales contains 6 families, 137 genera, and 1411 species. Hyde et al. (2020a) listed 14 families under Hypocreales, while, Wijayawardene et al. (2022) accepted 15 families in the order, where Cylindriaceae was additionally added. Earlier, Hyde et al. (2020a) had placed Cylindriaceae in class Xylariomycetidae. Samarakoon et al. (2022) agreed. Hence, Cylindriaceae should have been excluded from Hypocreales and placed in Xylariomycetidae. Xiao et al. (2022) recently introduced a new family Polycephalomycetaceae to Hypocreales.

<span class="mw-page-title-main">Pleosporales</span> Order of fungi

The Pleosporales is the largest order in the fungal class Dothideomycetes. By a 2008 estimate, it contained 23 families, 332 genera and more than 4700 species. The majority of species are saprobes on decaying plant material in fresh water, marine, or terrestrial environments, but several species are also associated with living plants as parasites, epiphytes or endophytes. The best studied species cause plant diseases on important agricultural crops e.g. Cochliobolus heterostrophus, causing southern corn leaf blight on maize, Phaeosphaeria nodorum causing glume blotch on wheat and Leptosphaeria maculans causing a stem canker on cabbage crops (Brassica). Some species of Pleosporales occur on animal dung, and a small number occur as lichens and rock-inhabiting fungi.

<span class="mw-page-title-main">Botryosphaeriales</span> Order of fungi

The Botryosphaeriales are an order of sac fungi (Ascomycetes), placed under class Dothideomycetes. Some species are parasites, causing leaf spot, plant rot, die-back or cankers, but they can also be saprophytes or endophytes. They occur world-wide on many hosts. For example, in China, infections related to Botryosphaeriales have been recorded on numerous hosts such as grapes, Caragana arborescens,Cercis chinensis, Eucalyptus, Chinese hackberry, blueberry, forest trees, and various other woody hosts.

Xylariomycetidae is a subclass of sac fungi.

<span class="mw-page-title-main">Melanommataceae</span> Family of fungi

The Melanommataceae are a family of fungi in the order Pleosporales. Taxa are widespread in temperate and subtropical regions, and are saprobic on wood and bark.

<span class="mw-page-title-main">Phaeosphaeriaceae</span> Family of fungi

The Phaeosphaeriaceae are a family of fungi in the order Pleosporales. Species in the family have a cosmopolitan distribution, and are generally nectrotrophic or saprobic on a wide range of plants.

The Didymosphaeriaceae are a family of fungi in the order Pleosporales. The family was erected by Anders Munk in 1953.

<i>Iodosphaeria</i> Genus of fungi

Iodosphaeria is a genus of fungi in the family Amphisphaeriaceae. Most of species of Iodosphaeria are saprobes that feed on dead leaves and twigs of various hosts such as the Argentine white pine. No species have been reported as pathogenic to hosts. As of January 2022, it contains eleven species.

The Graphostromataceae are a family of fungi in the order Xylariales. This was a monotypic family, containing the single genus Graphostroma, which in turn contains the single species Graphostroma platystoma.

<span class="mw-page-title-main">Bionectriaceae</span> Family of fungi

The Bionectriaceae are a family of fungi in the order Hypocreales. A 2008 estimate places 35 genera and 281 species in the family. Species in the family tend to grow on plant material, including woody debris, while some species associate with algae, bryophytes, or other fungi.

<i>Leptosillia</i> Genus of fungi

Leptosillia is a fungal genus in the monogeneric family of Leptosilliaceae. The genus was circumscribed by Austrian mycologist Franz Xaver Rudolf von Höhnel in 1928. As the genus name suggests, Leptosillia was considered to be closely related to the diaporthalean genus of Sillia.

<i>Pestalotiopsis</i> Genus of fungi

Pestalotiopsis is a genus of ascomycete fungi in the Sporocadaceae family.

The Amphisphaeriales are an order of fungi within the class Sordariomycetes and subclass Xylariomycetidae.

<span class="mw-page-title-main">Sporocadaceae</span> Family of fungi

The Sporocadaceae are a family of fungi, that was formerly in the order Xylariales. It was placed in the Amphisphaeriales order in 2020.

<i>Sporocadus</i> Genus of fungi

Sporocadus is a genus of plant pathogens in the family Sporocadaceae.

<i>Discosia</i> Genus of fungi

Discosia is a genus of plant pathogens in the family Sporocadaceae.

<i>Neopestalotiopsis</i> Genus of fungi

Neopestalotiopsis is a genus of plant pathogens in the family Sporocadaceae.

Conioscypha is a genus of terrestrial and freshwater fungi in the monotypic family Conioscyphaceae and the monotypic order Conioscyphales. They are found on decayed wood, leaves, or bamboo stems. Except for Conioscypha japonica which was isolated from dog skin fragments and hair in 2017.

Pleurotheciaceae is a family of ascomycetous fungi within the monotypic order of Pleurotheciales in the subclass Savoryellomycetidae and within the class Sordariomycetes.

<i>Neocamarosporium</i> Genus of fungi

Neocamarosporium is a genus of ascomycete fungi, as accepted by Wijayawardene et al. 2020. The species are typically halotolerant, being commonly found in saline environments like in saline water, hypersaline soils and especially in association with halophytes.

References

  1. ↑ Nannfeldt, J.A. (1932). "Studien über die morphologie und systematik der nichtlichenisierten inoperculaten Discomyceten" [Studies on the morphology and systematics of non-lichenized inoperculate discomycetes]. Nova Acta Regiae Societatis Scientiarum Upsaliensis. IV (in German). 8 (2): 1–368 [66].
  2. 1 2 3 4 Smith, Gavin J.D.; Edward, C.Y. Liew; Hyde, Kevin D. (2003). "The Xylariales: a monophyletic order containing 7 families". Fungal Diversity. 13: 185–218.
  3. ↑ Daranagama, Dinushani A.; Hyde, Kevin D.; Sir, Esteban B.; Thambugala, Kasun M.; Tian, Qing; Samarakoon, Milan C.; McKenzie, Eric H.C.; Jayasiri, Subashini C.; Tibpromma, Saowaluck; Bhat, Jayarama D.; Liu, XingZhong; Stadler, Marc (2018). "Towards a natural classification and backbone tree for Graphostromataceae, Hypoxylaceae, Lopadostomataceae and Xylariaceae". Fungal Diversity. 88 (1): 1–165. doi:10.1007/s13225-017-0388-y.
  4. ↑ Cosoveanu, Andrea; Rodriguez Sabina, Samuel; Cabrera, Raimundo (2018). "Fungi as Endophytes in Artemisia thuscula: juxtaposed elements of diversity and phylogeny". Journal of Fungi. 4 (17): 70–82. doi: 10.3390/jof4010017 . PMC   5872320 . PMID   29382076.
  5. ↑ Gary A. Strobel (Editor) Fungal Endophytes in Plants , p. 83, at Google Books
  6. 1 2 Samarakoon, Milan C.; Hyde, Kevin D.; Maharachchikumbura, Sajeewa S.N.; Stadler, Marc; Gareth Jones, E.B.; Promputtha, Itthayakorn; Suwannarach, Nakarin; Camporesi, Erio; Bulgakov, Timur S.; Liu, Jian-Kui (2022). "Taxonomy, phylogeny, molecular dating and ancestral state reconstruction of Xylariomycetidae (Sordariomycetes)". Fungal Diversity. 112 (1): 1–88. doi: 10.1007/s13225-021-00495-5 .
  7. ↑ Robinson, Aaron J.; Natvig, Donald O. (2019). "Diverse members of the Xylariales lack canonical mating-type regions". Fungal Genetics and Biology. 122: 47–52. doi: 10.1016/j.fgb.2018.12.004 . PMC   6321786 . PMID   30557613.
  8. 1 2 3 Becker, Kevin; Stadler, Marc (2021). "Recent progress in biodiversity research on the Xylariales and their secondary metabolism". The Journal of Antibiotics. 74 (1): 1–23. doi: 10.1038/s41429-020-00376-0 . PMC   7732752 . PMID   33097836.
  9. 1 2 Hyde, K.D.; Noorabadi, M.T.; Thiyagaraja, V.; He, M.Q.; Johnston, P.R.; Wijesinghe, S.N.; et al. (2024). "The 2024 Outline of Fungi and fungus-like taxa". Mycosphere. 15 (1): 5332–5337. doi:10.5943/mycosphere/15/1/25.
  10. ↑ Wendt, Lucile; Sir, Esteban Benjamin; Kuhnert, Eric; Heitkämper, Simone; Lambert, Christopher; Hladki, Adriana I.; Romero, Andrea I.; Luangsa-ard, J. Jennifer; Srikitikulchai, Prasert; Peršoh, Derek; Stadler, Marc (2018). "Resurrection and emendation of the Hypoxylaceae, recognised from a multigene phylogeny of the Xylariales". Mycological Progress. 17 (1–2): 115–154. doi: 10.1007/s11557-017-1311-3 .
  11. ↑ Miller, A.N.; Réblová, M. (2021). "Phylogenetic placement of Iodosphaeriaceae (Xylariales, Ascomycota), designation of an epitype for the type species of Iodosphaeria, I. phyllophila, and description of I. foliicola sp. nov". Fungal Systematics and Evolution: 49–64. doi: 10.3114/fuse.2021.08.05 . PMC   8687054 . PMID   35005572.
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