Basidiomycota

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Basidiomycota
Basidiomycetes from Ernst Haeckel's 1904 Kunstformen der Natur
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Subkingdom: Dikarya
Division: Basidiomycota
Moore, R.T. 1980[1]
Subdivisions/Classes
Agaricomycotina
Pucciniomycotina
Ustilaginomycotina

Basidiomycota (

Cryptococcus
, the human pathogenic yeast.

Basidiomycota are filamentous fungi composed of

DNA sequence
data.

Classification

A 2007 classification, adopted by a coalition of 67

mycologists recognized three subphyla (Pucciniomycotina, Ustilaginomycotina, Agaricomycotina) and two other class level taxa (Wallemiomycetes, Entorrhizomycetes) outside of these, among the Basidiomycota.[5] As now classified, the subphyla join and also cut across various obsolete taxonomic groups (see below) previously commonly used to describe Basidiomycota. According to a 2008 estimate, Basidiomycota comprise three subphyla (including six unassigned classes) 16 classes, 52 orders, 177 families, 1,589 genera, and 31,515 species.[6]
Wijayawardene et al. 2020 produced an update that recognized 19 classes (
Monilielliomycetes, Pucciniomycetes, Spiculogloeomycetes, Tremellomycetes, Tritirachiomycetes, Ustilaginomycetes and Wallemiomycetes) with multiple orders and genera.[7]

Traditionally, the Basidiomycota were divided into two classes, now obsolete:

Nonetheless these former concepts continue to be used as two types of

Ustilago maydis).[3]

Agaricomycotina

The

Dacrymycetes, and the Tremellomycetes.[9]

The class Wallemiomycetes is not yet placed in a subdivision, but recent genomic evidence suggests that it is a sister group of Agaricomycotina.[10][11]

Pucciniomycotina

The Pucciniomycotina include the rust fungi, the insect parasitic/symbiotic genus Septobasidium, a former group of smut fungi (in the Microbotryomycetes, which includes mirror yeasts), and a mixture of odd, infrequently seen, or seldom recognized fungi, often parasitic on plants. The eight classes in the Pucciniomycotina are Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes, Cryptomycocolacomycetes, Cystobasidiomycetes, Microbotryomycetes, Mixiomycetes, and Pucciniomycetes.[12]

Ustilaginomycotina

The Ustilaginomycotina are most (but not all) of the former smut fungi and the Exobasidiales. The classes of the Ustilaginomycotina are the Exobasidiomycetes, the Entorrhizomycetes, and the Ustilaginomycetes.[13]

Genera included

There are several genera classified in the Basidiomycota that are 1) poorly known, 2) have not been subjected to DNA analysis, or 3) if analysed phylogenetically do not group with as yet named or identified families, and have not been assigned to a specific family (i.e., they are incertae sedis with respect to familial placement). These include:

Typical life cycle

Sexual reproduction cycle of basidiomycetes
Basidiomycota life cycle
Cell cycle of a Dikaryotic basidiomycete

Unlike animals and plants which have readily recognizable male and female counterparts, Basidiomycota (except for the

hyphae. Typically haploid Basidiomycota mycelia fuse via plasmogamy and then the compatible nuclei migrate into each other's mycelia and pair up with the resident nuclei. Karyogamy is delayed, so that the compatible nuclei remain in pairs, called a dikaryon. The hyphae are then said to be dikaryotic. Conversely, the haploid mycelia are called monokaryons. Often, the dikaryotic mycelium is more vigorous than the individual monokaryotic mycelia, and proceeds to take over the substrate in which they are growing. The dikaryons can be long-lived, lasting years, decades, or centuries. The monokaryons are neither male nor female. They have either a bipolar (unifactorial) or a tetrapolar (bifactorial) mating system. This results in the fact that following meiosis, the resulting haploid basidiospores and resultant monokaryons, have nuclei that are compatible with 50% (if bipolar) or 25% (if tetrapolar) of their sister basidiospores (and their resultant monokaryons) because the mating genes must differ for them to be compatible. However, there are sometimes more than two possible alleles for a given locus, and in such species, depending on the specifics, over 90% of monokaryons could be compatible with each other.[citation needed
]

The maintenance of the dikaryotic status in dikaryons in many Basidiomycota is facilitated by the formation of

sterigmata
which are tapered spine-like projections on basidia, and are typically curved, like the horns of a bull. In some Basidiomycota the spores are not ballistic, and the sterigmata may be straight, reduced to stubs, or absent. The basidiospores of these non-ballistosporic basidia may either bud off, or be released via dissolution or disintegration of the basidia.

Scheme of a typical basidiocarp, the dipoid reproductive structure of a basidiomycete, showing fruiting body, hymenium and basidia.

In summary, meiosis takes place in a diploid basidium. Each one of the four haploid nuclei migrates into its own basidiospore. The basidiospores are ballistically discharged and start new haploid mycelia called monokaryons. There are no males or females, rather there are compatible thalli with multiple compatibility factors. Plasmogamy between compatible individuals leads to delayed karyogamy leading to establishment of a dikaryon. The dikaryon is long lasting but ultimately gives rise to either fruitbodies with basidia or directly to basidia without fruitbodies. The paired dikaryon in the basidium fuse (i.e. karyogamy takes place). The diploid basidium begins the cycle again.

Meiosis

Coprinopsis cinerea is a basidiomycete mushroom. It is particularly suited to the study of meiosis because meiosis progresses synchronously in about 10 million cells within the mushroom cap, and the meiotic prophase stage is prolonged. Burns et al.[14] studied the expression of genes involved in the 15-hour meiotic process, and found that the pattern of gene expression of C. cinerea was similar to two other fungal species, the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. These similarities in the patterns of expression led to the conclusion that the core expression program of meiosis has been conserved in these fungi for over half a billion years of evolution since these species diverged.[14]

double-strand breaks. The ability of C. neoformans and U. maydis to undergo meiosis may contribute to their virulence by repairing the oxidative DNA damage caused by their host's release of reactive oxygen species.[15][16]

Variations in lifecycles

Many variations occur: some variations are self-compatible and spontaneously form dikaryons without a separate compatible thallus being involved. These fungi are said to be homothallic, versus the normal heterothallic species with mating types. Others are secondarily homothallic, in that two compatible nuclei following meiosis migrate into each basidiospore, which is then dispersed as a pre-existing dikaryon. Often such species form only two spores per basidium, but that too varies. Following meiosis, mitotic divisions can occur in the basidium. Multiple numbers of basidiospores can result, including odd numbers via degeneration of nuclei, or pairing up of nuclei, or lack of migration of nuclei. For example, the chanterelle genus

Cryptococcus, four nuclei following meiosis remain in the basidium, but continually divide mitotically, each nucleus migrating into synchronously forming nonballistic basidiospores that are then pushed upwards by another set forming below them, resulting in four parallel chains of dry "basidiospores".[citation needed
]

Other variations occur: some as standard lifecycles (that themselves have variations within variations) within specific orders.[citation needed]

Rusts

Autoecious rusts complete their life-cycles on one host instead of two, and microcyclic rusts cut out one or more stages.[citation needed
]

Smuts

The characteristic part of the life-cycle of

Tilletia caries, the elongated haploid basidiospores form apically, often in compatible pairs that fuse centrally resulting in H-shaped diaspores which are by then dikaryotic. Dikaryotic conidia may then form. Eventually the host is infected by infectious hyphae. Teliospores form in host tissue. Many variations on these general themes occur.[citation needed
]

Smuts with both a yeast phase and an infectious hyphal state are examples of

Cryptococcus, e.g. Cryptococcus neoformans[19] and Cryptococcus gattii.[18]

The dimorphic Basidiomycota with yeast stages and the pleiomorphic rusts are examples of fungi with

Decapitatus flavidus propagules
called gemmae.

See also

References

  1. ^ Moore, R. T. (1980). "Taxonomic proposals for the classification of marine yeasts and other yeast-like fungi including the smuts". Botanica Marina. 23: 371.
  2. ^ "Basidiomycota". Dictionary.com Unabridged (Online). n.d.
  3. ^
    PMID 17506673
    .
  4. S2CID 84615057
    . Retrieved 16 January 2019.
  5. S2CID 4686378
    .
  6. ^ Kirk, Cannon & Stalpers 2008, pp. 78–79
  7. hdl:10481/61998
    .
  8. ^ "Lecture 7 : Ustilaginomycets" (PDF). Cpb-us-e1.wpmucdn.com. Archived (PDF) from the original on 2020-07-30. Retrieved 2 March 2022.
  9. ^ Kirk, Cannon & Stalpers 2008, p. 13
  10. PMID 24034603
    .
  11. PMID 22326418
    .
  12. ^ Kirk, Cannon & Stalpers 2008, p. 581
  13. ^ Kirk, Cannon & Stalpers 2008, pp. 717–718
  14. ^
    PMID 20885784
    .
  15. S2CID 3195603
    .
  16. PMID 18295550
    .
  17. PMID 12102002
    . Retrieved 2024-03-12.
  18. ^
    PMID 20224779
    .
  19. PMID 789347
    .
  20. ^ "Archived copy". Archived from the original on 2007-10-25. Retrieved 2007-09-13.{{cite web}}: CS1 maint: archived copy as title (link)
  21. ^ "Microsoft Word – Machnicki revised for pdf final august 24" (PDF). Archived from the original (PDF) on 27 September 2007. Retrieved 3 March 2022.
  22. ^ a b "LUXGENE.COM: The glow-in-the-dark website". Archived from the original on 2007-09-28. Retrieved 2007-09-13.
  23. ^ "Hohenbue". Archived from the original on 2006-12-21. Retrieved 2007-04-17.
  24. ^ "8knobs". Archived from the original on 2006-12-21. Retrieved 2007-04-17.

Sources

  • Kirk, P. M.; Cannon, P. F.; Stalpers, J. A. (2008). Dictionary of the Fungi (10th ed.). CABI.

External links

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